The document provides details about the syllabus for the course EE2301 Power Electronics. It includes 5 units:
1) Power Semiconductor Devices
2) Phase-Controlled Converters
3) DC to DC Converters
4) Inverters
5) AC to AC Converters
It lists the topics that will be covered in each unit along with the total number of periods (45) and references textbooks that will be used. It also provides short questions and answers related to the first two units on power semiconductor devices and phase-controlled converters.
3 phase half wave controlled converter with r Loadmechatronics jf
This document discusses three-phase converters that convert AC power to DC power for loads. It specifically describes three-phase half-wave controlled rectifiers, which are made up of three single-phase half-wave converters connected together. It provides the equation to calculate the average DC output voltage of a three-phase half-wave converter and discusses that the thyristor conducts from 30 degrees to 180 degrees for a resistive load. The document concludes by describing a problem to calculate firing angle, average/RMS load current, and efficiency for a 3-phase converter operating from a 230V 50Hz supply with a 10 ohm resistive load and 50% of maximum output voltage required.
The document discusses power system transients. It defines transients as pulses of very short duration but high intensity. Transients can be classified as ultra-fast, medium-fast, or slow depending on their speed. Causes of transients include lightning, switching operations, faults, and resonance. When a transmission line is energized, voltages build up gradually along it via traveling waves. The velocity and behavior of these waves are determined by the line's inductance and capacitance per unit length.
This document discusses methods for generating high direct current (DC) voltages, primarily for research in physics. It describes how rectifier circuits such as half-wave, full-wave, and voltage doubler configurations can be used to convert alternating current (AC) to high DC voltages of up to 100kV. Voltage doubler circuits are useful for producing higher voltages than full-wave rectifiers. Cascading multiple voltage doubler stages allows generating even higher DC outputs without changing the input transformer voltage. Special construction is needed for rectifier valves to withstand the high electric fields produced at voltages over 100kV.
The document discusses converter configurations and analyzes a 12 pulse converter. It begins by explaining pulse number and valve/switch types in converters. It then discusses how converter configuration is selected based on pulse number to maximize valve and transformer utilization. It provides equations for peak inverse voltage, utilization factor, and transformer rating calculations. Finally, it analyzes a 12 pulse converter, explaining how two transformers connected in star-star and star-delta configurations produce 12 pulses of output with each pulse having a 30 degree duration.
Gcsc gto thyristor controlled series capacitorLEOPAUL23
The document discusses the GTO Thyristor Controlled Series Capacitor (GCSC), which consists of a fixed capacitor in parallel with an anti-parallel GTO pair. The GCSC can continuously vary the voltage across the capacitor between zero and its maximum value by controlling the turn-off delay angle of the thyristor valve. It works by closing and opening the thyristor valve in synchronism with the supply frequency. The GCSC can operate in either voltage compensating mode, to maintain a rated compensating voltage over a range of line currents, or in reactance compensating mode, to maintain a maximum rated compensating reactance at any line current.
The concept of FACTS (Flexible Alternating Current Transmission System) refers to a family of power electronics-based devices able to enhance AC system controllability and stability and to increase power transfer capability.
Electrical fault is the deviation of voltages and currents from nominal values or states. Under normal operating conditions, power system equipment or lines carry normal voltages and currents which results in a safer operation of the system.
FACTS DEVICES AND POWER SYSTEM STABILITY pptMamta Bagoria
This presentation provides an overview of Flexible AC Transmission Systems (FACTS) and power system stability. It defines FACTS as using power electronics to control power flow and enhance transmission system capacity and stability. The document outlines different types of FACTS controllers including series compensation and shunt compensation. It also classifies power system stability into rotor angle stability, voltage stability, and frequency stability and discusses factors that can lead to losses of each type of stability.
3 phase half wave controlled converter with r Loadmechatronics jf
This document discusses three-phase converters that convert AC power to DC power for loads. It specifically describes three-phase half-wave controlled rectifiers, which are made up of three single-phase half-wave converters connected together. It provides the equation to calculate the average DC output voltage of a three-phase half-wave converter and discusses that the thyristor conducts from 30 degrees to 180 degrees for a resistive load. The document concludes by describing a problem to calculate firing angle, average/RMS load current, and efficiency for a 3-phase converter operating from a 230V 50Hz supply with a 10 ohm resistive load and 50% of maximum output voltage required.
The document discusses power system transients. It defines transients as pulses of very short duration but high intensity. Transients can be classified as ultra-fast, medium-fast, or slow depending on their speed. Causes of transients include lightning, switching operations, faults, and resonance. When a transmission line is energized, voltages build up gradually along it via traveling waves. The velocity and behavior of these waves are determined by the line's inductance and capacitance per unit length.
This document discusses methods for generating high direct current (DC) voltages, primarily for research in physics. It describes how rectifier circuits such as half-wave, full-wave, and voltage doubler configurations can be used to convert alternating current (AC) to high DC voltages of up to 100kV. Voltage doubler circuits are useful for producing higher voltages than full-wave rectifiers. Cascading multiple voltage doubler stages allows generating even higher DC outputs without changing the input transformer voltage. Special construction is needed for rectifier valves to withstand the high electric fields produced at voltages over 100kV.
The document discusses converter configurations and analyzes a 12 pulse converter. It begins by explaining pulse number and valve/switch types in converters. It then discusses how converter configuration is selected based on pulse number to maximize valve and transformer utilization. It provides equations for peak inverse voltage, utilization factor, and transformer rating calculations. Finally, it analyzes a 12 pulse converter, explaining how two transformers connected in star-star and star-delta configurations produce 12 pulses of output with each pulse having a 30 degree duration.
Gcsc gto thyristor controlled series capacitorLEOPAUL23
The document discusses the GTO Thyristor Controlled Series Capacitor (GCSC), which consists of a fixed capacitor in parallel with an anti-parallel GTO pair. The GCSC can continuously vary the voltage across the capacitor between zero and its maximum value by controlling the turn-off delay angle of the thyristor valve. It works by closing and opening the thyristor valve in synchronism with the supply frequency. The GCSC can operate in either voltage compensating mode, to maintain a rated compensating voltage over a range of line currents, or in reactance compensating mode, to maintain a maximum rated compensating reactance at any line current.
The concept of FACTS (Flexible Alternating Current Transmission System) refers to a family of power electronics-based devices able to enhance AC system controllability and stability and to increase power transfer capability.
Electrical fault is the deviation of voltages and currents from nominal values or states. Under normal operating conditions, power system equipment or lines carry normal voltages and currents which results in a safer operation of the system.
FACTS DEVICES AND POWER SYSTEM STABILITY pptMamta Bagoria
This presentation provides an overview of Flexible AC Transmission Systems (FACTS) and power system stability. It defines FACTS as using power electronics to control power flow and enhance transmission system capacity and stability. The document outlines different types of FACTS controllers including series compensation and shunt compensation. It also classifies power system stability into rotor angle stability, voltage stability, and frequency stability and discusses factors that can lead to losses of each type of stability.
The Unified Power Flow Controller (UPFC) was proposed in 1991 as a device to control real and reactive power flow in AC transmission systems using two voltage sourced converters. The UPFC can independently control parameters like voltage, impedance, and phase angle to regulate power flow. It consists of two back-to-back converters connected by a DC link that allow bidirectional real power flow and independent reactive power control at each converter. The UPFC can perform functions like voltage regulation, series compensation, phase shifting, and multifunctional power flow control by injecting a controlled compensating voltage into the transmission line.
This document discusses DC-DC converters known as choppers. It describes two types - step-down choppers and step-up choppers. A step-down chopper uses a thyristor switch to reduce input voltage to a lower output voltage for a load. Waveforms of the output voltage and current are shown. Different classes of choppers - Classes A through E - are defined based on the triggering schemes of the thyristors used. An example calculation is given to determine thyristor conduction period based on input voltage, output voltage, and operating frequency.
1. Shunt compensation involves connecting FACTS devices in parallel with transmission lines to act as controllable current sources.
2. There are two types of shunt compensation: shunt capacitive compensation improves power factor by injecting a leading current, while shunt inductive compensation increases power transfer capability by reducing voltage amplification.
3. Examples of FACTS devices for shunt compensation include STATCOM, SVC using TCR, TSC and TSR to continuously or stepwise vary the equivalent reactance.
Introduction
HVDC transmission lines have become commercially successful in India and many other nations after 1980. High Voltage Direct Current Transmission is an alternative to 3 phase 50 Hz AC transmission. Particular applications of HVDC transmission lines are as follows:
Long 2 terminal Bipolar High Power HVDC systems – They have following advantages
• Economy in capital cost.
• Better power control.
• Lower transmission losses.
• Energy conservation.
• Higher stability limit.
Back to back HVDC Coupling Stations between two independently controlled AC networks
• Technically superior.
• Better stability of AC networks at both ends.
• Excellent interconnection.
• Large scale blackouts in interconnected ac networks are prevented.
Long High power submarine cable
• No continuous charging currents.
Multi terminal HVDC interconnection system between 3 or more independently controlled ac networks
• Accurate and fast control of power exchange between 3 or more ac networks.
• No total blackouts.
• Higher stability limits.
• Lower losses.
• Energy conversation.
Protection and switch gear requirements
The protection and switch gear requirements of HVDC systems is quite different from that of AC systems. In HVDC systems, protection and control functions are integrated with the thyristor converter control. There are no HVDC circuit breakers. For normal operation and control and for protection from abnormal currents and voltages etc. thyristor control is employed. In the event of single pole to ground faults which are beyond the capability of thyristor control; the AC circuit breakers of the faulty pole are tripped after reducing the power flow and fault is isolated. All the present HVDC systems are without HVDC circuit breaker in the DC poles. Circuit breakers are provided on AC side of converter transformers.
However, the HVDC Switching Devices in form of Metallic Return Transfer Breaker are necessary in the earth return path in present 2 terminal HVDC systems for interrupting earth return currents during change over from earth return to pole return.
Artificial current interruption principle
The artificial current zero principle must be employed in HVDC switching devices for interrupting of DC arcs. The artificial current zeroes are produced in the LC oscillatory circuit in the loop of circuit breaker while opening the contacts. The arc is extinguished by the circuit breaker. The HVDC circuit Breaker Pole has ZnO arresters in parallel with the main CB for absorbing switching overvoltages. Even though the development of HVDC Circuit breakers have been technically successful, they are not commercially used due to their high cost.
Schematic of DC Switching System and Waveform of Idc with Artificial Current zeroes.
As the main breaker opens at t1, the DC arc is initiated between the contacts. Idc flows through the arc in the MB. As the Triggered Vacuum Gap sparks over, the parall
The load dispatch center monitors and controls the power system to ensure reliable power supply. It collects data using a SCADA system and oversees elements like generators, transformers, and transmission lines. The load dispatch center performs economic and secure operation of the power system, and works to restore power lines after faults. It is responsible for functions like load forecasting, outage monitoring, voltage regulation, load scheduling, and coordination between grids.
Generation of High D.C. Voltage (HVDC generation)RP6997
Generation of high dc voltage using different methods like half wave and full wave rectifier, voltage doubler circuits, voltage multiplier circuits, cockcroft-walton circuits and van de graaff generators.
The UPFC is a FACTS device that can control all three parameters of line power flow - voltage, impedance, and phase angle. It consists of two voltage source inverters, one connected in series with the transmission line and one connected in shunt. The shunt inverter controls reactive power flow and voltage, while the series inverter controls real and reactive power flow by injecting a controllable voltage in series with the line. Control schemes for the UPFC include phase angle control, cross-coupling control, and a generalized control scheme that provides damping against power swings for improved stability. The UPFC offers benefits like improved power transfer capacity, transient stability, and independent control of real and reactive power flows.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
1. Substations are facilities that link power generation stations to transmission systems and distribution systems by increasing or decreasing voltage levels through transformers.
2. Key components of substations include power transformers, current and potential transformers, circuit breakers, isolators, earth switches, lightning arrestors, and wave traps.
3. Power transformers increase or decrease voltage to allow for efficient transmission of power over long distances and distribution to customers, while current and potential transformers adapt measurements to instrumentation.
Infinite bus bar is one which keeps constant voltage and frequency although the load varies. Thus it may behave like a voltage source with zero internal impedance and infinite rotational inertia.
1) Streamer theory was proposed in 1940 by Rather, Meek and Loeb to explain phenomena not accounted for by Townsend's theory of gas breakdown, such as dependence on gas pressure and geometry.
2) Streamer theory describes how a single avalanche can develop into a spark discharge through distortion of the electric field by space charge, generating further avalanches cumulatively at the avalanche head.
3) Positive ions are left behind the rapidly advancing avalanche head, enhancing the field in front and reducing it behind, while the field is also enhanced between the tail and cathode. This leads to further space charge increase and field enhancement around the anode, forming a streamer connecting anode to cathode.
This document discusses four types of modifications that can be made to an existing power network to revise the Z-bus representation. Type 1 involves adding a branch impedance between a new bus and the reference bus. Type 2 adds a branch between a new bus and an existing bus. Type 3 adds a branch between an existing bus and the reference bus. Type 4 adds a branch between two existing buses. The document presents figures to illustrate each type and provides the corresponding equations to update the Z-bus matrix for the network.
1) The document discusses inductance in electrical conductors and transmission lines. It defines internal and external inductance and provides formulas to calculate them.
2) Formulas are provided for the inductance of a single-phase two-wire transmission line, as well as a three-phase line with symmetrical and unsymmetrical conductor spacing.
3) Bundled conductors are described as having multiple sub-conductors to reduce losses at high voltages and transmit more power efficiently.
Tripping and control of impulse generatorsFariza Zahari
The document discusses methods for tripping and controlling impulse generators. A simple method uses a three electrode gap in the first stage, where the central electrode is maintained at a potential between the top and bottom electrodes. Tripping is initiated by applying a pulse to a thyraton, which produces a negative pulse to trigger the three electrode gap. Modern methods instead use a trigatron, which requires a smaller voltage for operation. A trigatron consists of a high voltage sphere, earthed main sphere, and trigger electrode. Tripping is achieved by a pulse causing a spark between the trigger electrode and earthed sphere, inducing a spark across the main gap.
Grounding or earthing offers two principal advantages. First, it provides protection to the power system. Secondly, earthing of electrical equipment ensures the safety of the persons handling the equipment.
This document contains 51 questions and answers related to power electronics topics such as IGBTs, thyristors, power MOSFETs, power BJTs, choppers, and converters. Some key points addressed are:
- IGBTs are popular due to lower heat requirements, lower switching losses, and smaller snubber circuit needs compared to other devices.
- Thyristors can be turned on through forward voltage, gate, or light triggering and turned off once their current reaches zero.
- Power diodes have higher voltage, current, and power ratings than signal diodes and operate at higher speeds.
- IGBTs, power MOSFETs, and power BJ
The document summarizes electric traction systems used for railways. It discusses the types of electric traction which include DC traction using direct current from overhead lines or third rails, and AC traction using alternating current from overhead lines. It describes the components of electric locomotives like transformers, rectifiers, inverters, traction motors. It also discusses track electrification systems like single catenary construction and compound catenary construction. The document provides an overview of the key elements of electric traction systems used for rail transport.
The document discusses reactive power and voltage control in power systems. It defines voltage collapse as occurring when the system is unable to meet the reactive power demand, typically due to heavy loading, faults, or insufficient reactive power generation/compensation. Voltage collapse can be studied by examining the generation, transmission, and consumption of reactive power in the system. The nature of voltage collapse can be transient or long-term depending on the time scale of the disturbance and system components involved. Analytical methods for assessing voltage stability treat the system as a two-bus model and define a critical voltage and reactance value below which the system becomes unstable. Reactive power support measures are needed to maintain voltage stability.
DataShare - Pauline Ward to University of Edinburgh School of Chemistry - 3 f...University of Edinburgh
Talk targeted at researchers at the University of Edinburgh, explaining how they can use DataShare to publish their research results, and some of the benefits of doing so.
This document outlines the course contents for Electrical Machine Design II, including the design of various electric machines. It covers the design of 3-phase induction motors, including calculations for the stator, rotor, slots, windings and operating characteristics. The design of single-phase induction motors is also addressed, including auxiliary windings. Synchronous machine design is covered as well, including dimensions, magnetic circuits, field windings and performance evaluation. Design considerations for large, high voltage, high speed, and vertically operated alternators are discussed. The term work includes designing induction and synchronous machines, drawing schematics, and tutorials. Relevant textbooks on electrical machine design are also listed.
The Unified Power Flow Controller (UPFC) was proposed in 1991 as a device to control real and reactive power flow in AC transmission systems using two voltage sourced converters. The UPFC can independently control parameters like voltage, impedance, and phase angle to regulate power flow. It consists of two back-to-back converters connected by a DC link that allow bidirectional real power flow and independent reactive power control at each converter. The UPFC can perform functions like voltage regulation, series compensation, phase shifting, and multifunctional power flow control by injecting a controlled compensating voltage into the transmission line.
This document discusses DC-DC converters known as choppers. It describes two types - step-down choppers and step-up choppers. A step-down chopper uses a thyristor switch to reduce input voltage to a lower output voltage for a load. Waveforms of the output voltage and current are shown. Different classes of choppers - Classes A through E - are defined based on the triggering schemes of the thyristors used. An example calculation is given to determine thyristor conduction period based on input voltage, output voltage, and operating frequency.
1. Shunt compensation involves connecting FACTS devices in parallel with transmission lines to act as controllable current sources.
2. There are two types of shunt compensation: shunt capacitive compensation improves power factor by injecting a leading current, while shunt inductive compensation increases power transfer capability by reducing voltage amplification.
3. Examples of FACTS devices for shunt compensation include STATCOM, SVC using TCR, TSC and TSR to continuously or stepwise vary the equivalent reactance.
Introduction
HVDC transmission lines have become commercially successful in India and many other nations after 1980. High Voltage Direct Current Transmission is an alternative to 3 phase 50 Hz AC transmission. Particular applications of HVDC transmission lines are as follows:
Long 2 terminal Bipolar High Power HVDC systems – They have following advantages
• Economy in capital cost.
• Better power control.
• Lower transmission losses.
• Energy conservation.
• Higher stability limit.
Back to back HVDC Coupling Stations between two independently controlled AC networks
• Technically superior.
• Better stability of AC networks at both ends.
• Excellent interconnection.
• Large scale blackouts in interconnected ac networks are prevented.
Long High power submarine cable
• No continuous charging currents.
Multi terminal HVDC interconnection system between 3 or more independently controlled ac networks
• Accurate and fast control of power exchange between 3 or more ac networks.
• No total blackouts.
• Higher stability limits.
• Lower losses.
• Energy conversation.
Protection and switch gear requirements
The protection and switch gear requirements of HVDC systems is quite different from that of AC systems. In HVDC systems, protection and control functions are integrated with the thyristor converter control. There are no HVDC circuit breakers. For normal operation and control and for protection from abnormal currents and voltages etc. thyristor control is employed. In the event of single pole to ground faults which are beyond the capability of thyristor control; the AC circuit breakers of the faulty pole are tripped after reducing the power flow and fault is isolated. All the present HVDC systems are without HVDC circuit breaker in the DC poles. Circuit breakers are provided on AC side of converter transformers.
However, the HVDC Switching Devices in form of Metallic Return Transfer Breaker are necessary in the earth return path in present 2 terminal HVDC systems for interrupting earth return currents during change over from earth return to pole return.
Artificial current interruption principle
The artificial current zero principle must be employed in HVDC switching devices for interrupting of DC arcs. The artificial current zeroes are produced in the LC oscillatory circuit in the loop of circuit breaker while opening the contacts. The arc is extinguished by the circuit breaker. The HVDC circuit Breaker Pole has ZnO arresters in parallel with the main CB for absorbing switching overvoltages. Even though the development of HVDC Circuit breakers have been technically successful, they are not commercially used due to their high cost.
Schematic of DC Switching System and Waveform of Idc with Artificial Current zeroes.
As the main breaker opens at t1, the DC arc is initiated between the contacts. Idc flows through the arc in the MB. As the Triggered Vacuum Gap sparks over, the parall
The load dispatch center monitors and controls the power system to ensure reliable power supply. It collects data using a SCADA system and oversees elements like generators, transformers, and transmission lines. The load dispatch center performs economic and secure operation of the power system, and works to restore power lines after faults. It is responsible for functions like load forecasting, outage monitoring, voltage regulation, load scheduling, and coordination between grids.
Generation of High D.C. Voltage (HVDC generation)RP6997
Generation of high dc voltage using different methods like half wave and full wave rectifier, voltage doubler circuits, voltage multiplier circuits, cockcroft-walton circuits and van de graaff generators.
The UPFC is a FACTS device that can control all three parameters of line power flow - voltage, impedance, and phase angle. It consists of two voltage source inverters, one connected in series with the transmission line and one connected in shunt. The shunt inverter controls reactive power flow and voltage, while the series inverter controls real and reactive power flow by injecting a controllable voltage in series with the line. Control schemes for the UPFC include phase angle control, cross-coupling control, and a generalized control scheme that provides damping against power swings for improved stability. The UPFC offers benefits like improved power transfer capacity, transient stability, and independent control of real and reactive power flows.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
1. Substations are facilities that link power generation stations to transmission systems and distribution systems by increasing or decreasing voltage levels through transformers.
2. Key components of substations include power transformers, current and potential transformers, circuit breakers, isolators, earth switches, lightning arrestors, and wave traps.
3. Power transformers increase or decrease voltage to allow for efficient transmission of power over long distances and distribution to customers, while current and potential transformers adapt measurements to instrumentation.
Infinite bus bar is one which keeps constant voltage and frequency although the load varies. Thus it may behave like a voltage source with zero internal impedance and infinite rotational inertia.
1) Streamer theory was proposed in 1940 by Rather, Meek and Loeb to explain phenomena not accounted for by Townsend's theory of gas breakdown, such as dependence on gas pressure and geometry.
2) Streamer theory describes how a single avalanche can develop into a spark discharge through distortion of the electric field by space charge, generating further avalanches cumulatively at the avalanche head.
3) Positive ions are left behind the rapidly advancing avalanche head, enhancing the field in front and reducing it behind, while the field is also enhanced between the tail and cathode. This leads to further space charge increase and field enhancement around the anode, forming a streamer connecting anode to cathode.
This document discusses four types of modifications that can be made to an existing power network to revise the Z-bus representation. Type 1 involves adding a branch impedance between a new bus and the reference bus. Type 2 adds a branch between a new bus and an existing bus. Type 3 adds a branch between an existing bus and the reference bus. Type 4 adds a branch between two existing buses. The document presents figures to illustrate each type and provides the corresponding equations to update the Z-bus matrix for the network.
1) The document discusses inductance in electrical conductors and transmission lines. It defines internal and external inductance and provides formulas to calculate them.
2) Formulas are provided for the inductance of a single-phase two-wire transmission line, as well as a three-phase line with symmetrical and unsymmetrical conductor spacing.
3) Bundled conductors are described as having multiple sub-conductors to reduce losses at high voltages and transmit more power efficiently.
Tripping and control of impulse generatorsFariza Zahari
The document discusses methods for tripping and controlling impulse generators. A simple method uses a three electrode gap in the first stage, where the central electrode is maintained at a potential between the top and bottom electrodes. Tripping is initiated by applying a pulse to a thyraton, which produces a negative pulse to trigger the three electrode gap. Modern methods instead use a trigatron, which requires a smaller voltage for operation. A trigatron consists of a high voltage sphere, earthed main sphere, and trigger electrode. Tripping is achieved by a pulse causing a spark between the trigger electrode and earthed sphere, inducing a spark across the main gap.
Grounding or earthing offers two principal advantages. First, it provides protection to the power system. Secondly, earthing of electrical equipment ensures the safety of the persons handling the equipment.
This document contains 51 questions and answers related to power electronics topics such as IGBTs, thyristors, power MOSFETs, power BJTs, choppers, and converters. Some key points addressed are:
- IGBTs are popular due to lower heat requirements, lower switching losses, and smaller snubber circuit needs compared to other devices.
- Thyristors can be turned on through forward voltage, gate, or light triggering and turned off once their current reaches zero.
- Power diodes have higher voltage, current, and power ratings than signal diodes and operate at higher speeds.
- IGBTs, power MOSFETs, and power BJ
The document summarizes electric traction systems used for railways. It discusses the types of electric traction which include DC traction using direct current from overhead lines or third rails, and AC traction using alternating current from overhead lines. It describes the components of electric locomotives like transformers, rectifiers, inverters, traction motors. It also discusses track electrification systems like single catenary construction and compound catenary construction. The document provides an overview of the key elements of electric traction systems used for rail transport.
The document discusses reactive power and voltage control in power systems. It defines voltage collapse as occurring when the system is unable to meet the reactive power demand, typically due to heavy loading, faults, or insufficient reactive power generation/compensation. Voltage collapse can be studied by examining the generation, transmission, and consumption of reactive power in the system. The nature of voltage collapse can be transient or long-term depending on the time scale of the disturbance and system components involved. Analytical methods for assessing voltage stability treat the system as a two-bus model and define a critical voltage and reactance value below which the system becomes unstable. Reactive power support measures are needed to maintain voltage stability.
DataShare - Pauline Ward to University of Edinburgh School of Chemistry - 3 f...University of Edinburgh
Talk targeted at researchers at the University of Edinburgh, explaining how they can use DataShare to publish their research results, and some of the benefits of doing so.
This document outlines the course contents for Electrical Machine Design II, including the design of various electric machines. It covers the design of 3-phase induction motors, including calculations for the stator, rotor, slots, windings and operating characteristics. The design of single-phase induction motors is also addressed, including auxiliary windings. Synchronous machine design is covered as well, including dimensions, magnetic circuits, field windings and performance evaluation. Design considerations for large, high voltage, high speed, and vertically operated alternators are discussed. The term work includes designing induction and synchronous machines, drawing schematics, and tutorials. Relevant textbooks on electrical machine design are also listed.
This document summarizes a seminar presentation on current source inverters (CSI). It introduces CSI and compares them to voltage source inverters. CSI use thyristors as self-commutating switching devices and do not require antiparallel diodes for current reversal. The document outlines the contents which include single phase CSI with ideal switches, advantages and disadvantages of CSI, single phase capacitor commutated CSI, and single phase auto sequential commutated inverter. Advantages of CSI include not requiring feedback diodes, simple commutation, and inherent short circuit protection for the supply. Disadvantages include high reverse voltages requiring devices like SCRs and continuous discharging of commutating
This document was prepared by C. Gokul, an assistant professor in the senior grade of electrical and electronics engineering at Velalar College of Engineering and Technology in Erode. It does not contain any other information besides repeating C. Gokul's name and credentials three times.
This document contains lecture notes on the fundamentals of electrical machine design from the EE-1352 ELECTRICAL MACHINE DESIGN course. It defines electrical machine design as the creative physical realization of theoretical concepts to produce machines that perform specified tasks with optimum economy and efficiency. The notes discuss basic considerations in developing a design including the design base, specifications, design transfer, and information updating. It also outlines major considerations like lower cost, durability, and meeting performance criteria, as well as limitations in design such as magnetic saturation, temperature rise, insulation, and customer specifications. Finally, it describes the basic structure of electrical machines including the magnetic, electric, dielectric, thermal, and mechanical circuits.
The document outlines the aims, objectives, and units of an electrical machine design course. The aims are to obtain complete dimensions of machine parts to provide to manufacturers, with goals of lower cost, weight, and size while achieving better performance. The objectives are to familiarize students with electrical materials properties, magnetic and electric fields laws, circuit laws, electromagnetic induction laws, magnetic circuits calculations, and machine construction and behavior. The 5 units cover introduction, DC machine design, transformer design, induction motor design, and synchronous machine design.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise boosts blood flow, releases endorphins, and promotes changes in the brain which help regulate emotions and stress levels.
The document discusses the 8085 microprocessor. It describes that the 8085 is an 8-bit microprocessor that can address 64KB of memory using 40 pins that operate at 5V with a maximum frequency of 3MHz. It has registers, ALU, instruction decoder, address buffer and other functional blocks. The registers include general purpose registers, temporary registers, flags register and program counter and stack pointer. The document also discusses the addressing modes, instruction formats and types of instructions of the 8085 microprocessor.
This document discusses the classification and operation of different types of electrical machines. It begins by classifying electrical machines as either static machines like transformers, or rotating machines like DC and AC machines. Within rotating machines, it further divides them into DC machines like DC generators and motors, and AC machines like asynchronous and synchronous machines. The document then focuses on describing the basic components and working principles of DC generators and DC motors. It explains how DC generators use electromagnetic induction to convert mechanical energy to electrical energy, and how DC motors convert electrical energy back to mechanical energy using the interaction of magnetic and electric fields.
This document discusses power electronics and provides an overview of key concepts:
1. Power electronics refers to controlling and converting electrical power using power semiconductor devices like SCRs. Main applications include rectification, inversion, DC-DC conversion, and AC-AC conversion.
2. Rectification can be uncontrolled using diodes or controlled using SCRs. Common rectifier configurations include single and three-phase bridge rectifiers. Inversion converts DC to AC using devices like SCRs, IGBTs, and MOSFETs.
3. DC-DC conversion is commonly done using switch-mode power supplies with devices like BJTs and MOSFETs. AC-AC conversion using cycloconverters
This document outlines and describes the key components and operating principles of three-phase induction motors, which are widely used in industrial applications due to their continuous operation. It discusses the main types of electrical machines and induction motors, including squirrel cage and slip ring induction motors. The document explains the basic working principle of three-phase induction motors, involving the generation of a rotating magnetic field in the stator that induces current in the rotor. It also describes the main components of three-phase induction motors such as the frame, stator, rotor, and windings.
The document discusses the typical parts and structure of a report. It outlines the key sections as the title page, table of contents, executive summary, introduction, findings, conclusions, recommendations, bibliography/references, and appendices. It focuses on explaining the introduction section in detail. The introduction typically includes the purpose, background, method of investigation, and scope. It provides examples and emphasizes using the present tense for purpose and past tense for background. The method discusses primary and secondary sources of data.
This document contains questions and answers related to power electronics devices and converters. It begins with definitions of key power electronics terms:
- IGBT is popular due to lower switching losses and smaller snubber circuit requirements.
- Thyristors can be turned on through forward voltage, gate, dv/dt, temperature, or light triggering.
- Power diodes have higher voltage, current, and power ratings than signal diodes due to a drift region construction.
- IGBTs, power MOSFETs, and power BJTs are voltage, voltage, and current controlled devices respectively due to how their output current is controlled by their input signals.
- There are N-channel and P-channel
This document contains questions and answers related to power electronics topics like phase controlled converters. Some key points:
- Phase controlled rectifiers convert fixed AC voltage to variable DC voltage by controlling the firing delay angle. Common applications include motor drives, traction systems, and process control.
- Freewheeling diodes improve input power factor and output current waveform quality in controlled rectifiers.
- Single phase bridge converters have advantages over midpoint converters like lower peak inverse voltages on SCRs and lower transformer ratings.
- Firing circuits for line commutated converters include UJT, cosine wave crossing pulse timing control, and digital schemes.
- Six-pulse converters have simpler commutation and reduced lower order
The document provides questions and answers related to power electronics topics such as IGBTs, thyristors, power diodes, MOSFETs, choppers, and inverters. Some key highlights include:
IGBTs are popular due to their lower heat requirements and switching losses compared to other devices. Thyristors can be turned on through various methods including forward voltage, gate, and light triggering. Power diodes have higher voltage, current, and power ratings than signal diodes. IGBTs, MOSFETs, and BJTs are voltage, voltage, and current controlled devices respectively based on their gate/base characteristics. PWM is a common control method for inverters and choppers
The document contains short questions and answers related to power electronics topics like IGBTs, thyristors, power diodes, power MOSFETs, choppers, inverters, and AC voltage controllers. Some key points covered include:
- IGBT is popular due to lower heat requirements and switching losses compared to other power devices.
- Thyristors can be turned on through various methods including forward voltage, gate, and light triggering.
- Power diodes have higher voltage, current, and power ratings than signal diodes.
- Power devices like IGBT, MOSFET and thyristor are voltage controlled while BJT is current controlled.
- Choppers provide
Industrial electronics 1 marks- polytechnicSukesh R
The document discusses power electronic devices such as SCR, IGBT, MOSFET and GTO. It provides definitions of key terms related to these devices such as triggering, gate triggering, latching current, and applications. Specific topics covered include:
1. SCR, IGBT, MOSFET and GTO are power semiconductor switching devices. SCR can be triggered through its gate or by increasing voltage.
2. Inverters, choppers, and UPS systems are discussed as applications that use these devices to convert power efficiently.
3. Forced and natural commutation methods are described for turning devices off in different circuit configurations.
The document discusses programmable logic controllers (PLCs) and their applications in industrial electronics. It provides definitions and explanations of key concepts such as:
1) PLCs use programmable memory to store instructions to implement logic, timing and sequencing functions to control machines and processes.
2) Relays are electrically operated switches used to control high voltage/current devices with low voltage/current control signals in PLC systems.
3) PLC programming uses ladder logic diagrams to create control programs that represent the logical functions of relay-based hardwired controllers.
Industrial electronics 1 marks- polytechnicSukesh R
The document discusses various power semiconductor devices and their applications. It provides definitions and explanations of silicon controlled rectifier (SCR), insulated gate bipolar transistor (IGBT), gate turn-off thyristor (GTO), metal-oxide-semiconductor field-effect transistor (MOSFET), and other related terms. Some key applications mentioned include motor drives, UPS systems, static breakers, and industrial uses. The document also covers triggering mechanisms, commutation methods, and inverters.
Power electronics deals with applying electronic principles to power-level situations rather than signal-level. It involves devices like power diodes, thyristors (SCRs), and transistors (BJT, MOSFET, IGBT) that can control high currents and voltages. A thyristor maintains conduction below its holding current and latches on above its latching current. Snubber circuits protect thyristors from high dv/dt. Controlled rectifiers use thyristors to vary DC output voltage. Choppers vary DC voltage using switching circuits. Inverters convert DC to AC. AC voltage controllers vary AC output voltage using phase control or on-off control of thyristors. Cycloconverters directly convert AC power
High Voltage Direct Current Transmission Systems 2Mark MaterialsSanthosh Kumar
The document provides information about HVDC transmission, including:
1. It lists two merits of AC transmission (power can be generated at high voltages, maintenance of AC substations is easy and cheaper) and two merits of DC transmission (it requires only two conductors, there is no skin effect).
2. It discusses types of DC link including monopolar, bipolar, and homopolar links.
3. It lists types of power devices used for HVDC transmission including thyristor, IGBT, GTO, LTT, and MCT.
4. It provides advantages and disadvantages of HVDC transmission such as full control over power, reduced transmission lines, and inability to change voltage
SPEED CONTROL OF SEPARATELY EXCITED DC MOTOR USING POWER ELECTRONIC CONVERTER ijiert bestjournal
In a modern technology the use of power electronic devices in the control strategies of
electrical drives is increasing. The speed of a DC motor can be varied by controlling the field
flux, the armature resistance or the terminal voltage applied to the armature circuit. The three
most common speed control methods are field resistance control, armature voltage control,
and armature resistance control. But here a technique of drive has been used for DC motor’s
speed control is chopper and some power electronics devices. It has been shown here the use
of chopper and power electronics devices which paves the way of controlling also torque and
speed characteristics of DC motor. Now the simulation of model is done and analysed in
MATLAB (Simulink) under varying speed and torque condition
This document contains 68 questions and answers related to power electronics interview questions. It covers topics like IGBTs, thyristors, power diodes, MOSFETs, BJTs, snubber circuits, choppers, controlled rectifiers, inverters, and PWM control. The questions define key power electronics terms and concepts and discuss the advantages and applications of different power devices and converter topologies.
IRJET- Design and Implementation of Isolated Multi-Output Flyback ConverterIRJET Journal
This document describes the design and implementation of an isolated multi-output flyback converter. A flyback converter uses a single switch and transformer to provide isolated output voltages from an input source. The designed converter uses a toroidal transformer with multiple secondary windings to generate multiple isolated output voltages at fixed levels. Simulation results and specifications for the transformer, switch, and outputs are provided. The flyback converter provides an efficient and low-cost solution for applications requiring multiple isolated low-power DC outputs.
This document summarizes a research paper on a novel soft switching LCL-T buck DC-DC converter system. The proposed converter uses an LCL-T topology with four switches to step down the input voltage. It connects capacitors in series with the input to generate a midpoint voltage of Vin/2, allowing each switch to experience only half the input voltage during operation. Simulation results show this converter achieves zero voltage switching and reduces switching losses compared to a conventional full bridge buck converter. Both open and closed loop models are developed and simulated in MATLAB, demonstrating constant output voltage regulation can be achieved.
This document provides an overview of power electronics. It discusses different types of power electronic converters including rectifiers, inverters, DC-DC converters, and AC-AC converters. It also covers topics like harmonics, semiconductor devices used in power electronics, and applications of power electronics. The document is divided into multiple chapters that go into further details on specific topics like diode and thyristor rectifiers, Fourier analysis, and effects of harmonics on power system components.
This document provides an overview of power electronics. It discusses different types of power electronic converters including rectifiers, inverters, DC-DC converters, and AC-AC converters. It also covers topics like harmonics, semiconductor devices used in power electronics, and applications of power electronics. The document contains chapters that go into more detail on specific topics like diode rectifiers, thyristor rectifiers, Fourier analysis, and more.
Speed Control Of Separately Excited Dc Motor Using A High Efficiency Flyback ...IJERA Editor
This paper deals with Speed control of separately excited DC motor using flyback converter with a new non complementary active clamp control method to achieve soft switching and high efficiency for heavy motor load and light load conditions. This is quite attractive for low power application with universal ac inputs, such as external adaptors. With the proposed control technique, the energy in the leakage inductance can be fully recycled. The soft switching can be achieved for the main switch and the absorbed leakage energy is transferred to the output and input side. In the Proposed model the resistive and DC motor is connected to flyback converter and it is simulated with different nominal voltages and rated speed is controlled at different levels for the N-type active clamp flyback converter and P-type active clamp flyback converter respectively. N-type active clamp flyback converter is suitable for high speed variation applications and P-type active clamp flyback converter is suitable for low speed variation applications.
This document provides an overview of the Power Electronics 17EC73 subject. It discusses the key topics that will be covered, including the basic theory of power semiconductor devices, practical applications of devices in power electronic systems, AC-DC and DC-DC conversion circuits. It also outlines the objectives and outcomes of Module 1, which will cover the construction, characteristics and applications of power devices and power electronic converters. The document then provides details on the history and applications of power electronics, as well as the characteristics, types and design of key power semiconductor devices and power electronic circuits.
This document provides an overview of the Power Electronics 17EC73 subject. It discusses the key topics that will be covered, including the basic theory of power semiconductor devices, practical applications of devices in power electronic systems, AC-DC and DC conversion circuits. It also outlines the objectives and outcomes of Module 1, which will cover the construction, characteristics and applications of power devices and different power electronic converter types.
Design & Implementation of Zero Voltage Switching Buck ConverterIJERA Editor
Zero voltage switching (ZVS) buck converter is more preferable over hard switched buck converter for low power, high frequency DC-DC conversion applications. In Zero voltage switching converter, turn on & turn off of a switch occurs at zero voltage that results in lower switching losses. In this converter soft switching is achieved by using resonant components. The optimal values of resonant components are determined by using electric functions derived from circuit configuration. This type of soft switched resonant converter offers very low electromagnetic interference (EMI).This study presents the circuit configuration with least components to realize highly efficient zero voltage switching resonant converter. It’s feasibility is confirmed with the developed proto type model and experimental results are verified.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
1. OM SATHI
1
EE2301 – POWER ELECTRONICS
1.1 SYLLABUS
EE2301 POWER ELECTRONICS 3 0 0 3
1. POWER SEMI-CONDUCTOR DEVICES 9
Study of switching devices, - Frame, Driver and snubber circuit of SCR, TRIAC,
BJT, IGBT, MOSFET,- Turn-on and turn-off characteristics, switching losses,
Commutation circuits for SCR,
2. PHASE-CONTROLLED CONVERTERS 9
2-pulse, 3-pulse and 6-pulse converters – Effect of source inductance – performance
parameters – Reactive power control of cnverters – Dual converters - Battery
charger.
3. DC TO DC CONVERTER 9
Step-down and step-up chopper – Time ratio control and current limit control –
Buck, boost, buck-boost converter, concept of Resonant switching – SMPS.
4. INVERTERS 9
Single phase and three phase (both 1200
mode and 1800
mode) inverters – PWM
techniques: Sinusoidal PWM, modified sinusoidal PWM - multiple PWM –
Introduction to space vector modulations - Voltage and harmonic control – Series
resonant inverter – Current source inverter.
5. AC TO AC CONVERTERS 9
Single phase AC voltage controllers – Multistage sequence control - single and
three phase cycloconverters –Introduction to Integral cycle control, Power factor
control and Matrix converters.
TOTAL : 45 PERIODS
TEXT BOOKS
1. M.H. Rashid, „Power Electronics: Circuits, Devices and Applications‟,
Pearson Education, PHI Third edition, New Delhi 2004.
2. Philip T.Krein, “Elements of Power Electronics” Oxford University Press, 2004 Edition.
REFERENCES
2. Ashfaq Ahmed Power Electronics for Technology Pearson Education, Indian reprint,
2003.
3. P.S.Bimbra “Power Electronics” Khanna Publishers, third Edition 2003.
3. Ned Mohan, Tore.M.Undeland, William.P.Robbins, „Power Electronics: Converters,
Applications and Design‟, John Wiley and sons, third edition, 2003.
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1.2 SHORT QUESTIONS AND ANSWERS
UNIT-I
POWER SEMI-CONDUCTOR DEVICES
1. Why IGBT is very popular nowadays?
a. Lower hate requirements
b. Lower switching losses
c. Smaller snubbed circuit requirements
2. What are the different methods to turn on the thyristor?
a. Forward voltage triggering
b. Gate triggering
c. dv/dt triggering
d. Temperature triggering
e. Light triggering
3. What is the difference between power diode and signal diode?
Power diode Signal diode
1.Constructed with n-layer, called
drift region between p+ layer and
n+ layer.Drift region is not present.
2.The voltage, current and power
ratings are higher.Lower3.Power diodes operate at high speeds. Operates at higher
switching speed.
4. IGBT is a voltage controlled device. Why?
Because the controlling parameter is gate-emitter voltage.
5. Power MOSFET is a voltage controlled device. Why?
Because the output (drain) current can be controlled by gate-source voltage.
6. Power BJT is a current controlled device. Why?
Because the output (collector) current can be controlled by base current.
7. What are the different types of power MOSFET?
a. N-channel MOSFET
b. P-channel MOSFET
8. How can a thyristor turned off?
A thyristor can be turned off by making the current flowing through it to zero.
9. Define latching current.
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The latching current is defined as the minimum value of anode current which it
must attain during turn on process to maintain conduction when gate signal is removed.
10. Define holding current.
The holding current is defined as the minimum value of anode current below which
it must fall to for turning off the thyristor.
11. What is a snubber circuit?
It consists of a series combination of a resistor and a capacitor in parallel with the
thyristors. It is mainly used for dv / dt protection.
12. What losses occur in a thyristor during working conditions?
a. Forward conduction losses
b. Loss due to leakage current during forward and reverse blocking.
c. Switching losses at turn-on and turn-off.
d. Gate triggering loss.
13. Define hard-driving or over-driving.
When gate current is several times higher than the minimum gate current required, a
thyristor is said to be hard-fired or over-driven. Hard-firing of a thyristor reduces its turn-on
time and enhances its di/dt capability.
14. Define circuit turn off time.
It is defined as the time during which a reverse voltage is applied across the
thyristor during its commutation process.
15. Why circuit turn off time should be greater than the thyristor turn-off time?
Circuit turn off time should be greater than the thyristor turn-off time for reliable
turn-off, otherwise the device may turn-on at an undesired instant, a process called
commutation failure.
17. What is the turn-off time for converter grade SCRs and inverter grade SCRs?
Turn-off time for converter grade SCRs is 50 – 100 ms turn-off time for converter
grade SCRs and inverter grade SCRs and for inverter grade SCRs is 3 – 50 ms.
18. What are the advantages of GTO over SCR?
a. Elimination of commutation of commutating components in forced commutation,
resulting in reduction in cost, weight and volume.
b. Reduction in acoustic noise and electromagnetic noise due to elimination of
commutation chokes.
c. Faster turn-off, permitting high switching frequencies.
d. Improved efficiency of the converters.
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19. What is meant by phase controlled rectifier?
It converts fixed ac voltage into variable dc voltage.
20. Mention some of the applications of controlled rectifier.
a. Steel rolling mills, printing press, textile mills and paper mills employing dc
motor drives.
b. DC traction
c. Electro chemical and electro-metallurgical process
d. Portable hand tool drives
e. Magnet power supplies
f. HVDC transmission system
PART- B
1. a) Discuss the different modes of operation of thyristor with the help of static
VI characteristics. (8)
1. b) Explain the construction of SCR with neat sketch. (8)
2. Draw the switching characteristics of SCR and explain it. (16)
3. Discuss the different modes of operation of TRIAC with the help of VI
characteristics. (16)
4. Explain the switching characteristics of TRIAC (16)
5. With the help of neat diagram explain the operation of BJT. (16)
UNIT-II
PHASE-CONTROLLED CONVERTERS
1. What is the function of freewheeling diodes in controlled rectifier?
It serves two process.
a. It prevents the output voltage from becoming negative.
b. The load current is transferred from the main thyristors to the freewheeling diode,
thereby allowing all of its thyristors to regain their blocking states.
2. What are the advantages of freewheeling diodes in a controlled in a controlled
rectifier?
a. Input power factor is improved.
b. Load current waveform is improved and thus the load performance is better.
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3. What is meant by delay angle?
The delay angle is defined as the angle between the zero crossing of the input
voltage and the instant the thyristors is fired.
4. What are the advantages of single phase bridge converter over single phase mid-
point converter?
a. SCRs are subjected to a peak-inverse voltage of 2Vm in a fully controlled bridge
rectifier. Hence for same voltage and current ratings of SCrs, power handled by
mid-point configuration is about
b. In mid-point converter, each secondary winding should be able to supply the load
power. As such, the transformer rating in mid-point converter is double the load
rating.
5. What is commutation angle or overlap angle?
The commutation period when outgoing and incoming thyristors are conducting
isknown as overlap period. The angular period, when both devices share conduction is
known as the commutation angle or overlap angle.
6. What are the different methods of firing circuits for line commutated converter?
a. UJT firing circuit.
b. The cosine wave crossing pulse timing control.
c. Digital firing schemes.
7. Give an expression for average voltage of single phase semiconverters.
Average output voltage Vdc = (Vm / _) (1 + cos _ ).
8. What is meant by input power factor in controlled rectifier?
The input power factor is defined as the ratio of the total mean input power to
thetotal RMS input volt-amperes.
PF = ( V1 I1 cos _1 ) / ( Vrms Irms) where V1 = phase voltage, I1 =
fundamentalcomponent of the supply current, _1 = input displacement angle, Irms = supply
rms current.
9. What are the advantages of six pulse converter?
a. Commutation is made simple.
b. Distortion on the ac side is reduced due to the reduction in lower order
harmonics.
c. Inductance reduced in series is considerably reduced.
10. What is meant by commutation?
It is the process of changing the direction of current flow in a particular path of the
circuit. This process is used in thyristors for turning it off.
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11. What are the types of commutation?
a. Natural commutation
b. Forced commutation
12. What is meant by natural commutation?
Here the current flowing through the thyristor goes through a natural zero and
enable the thyristor to turn off.
13. What is meant by forced commutation?
In this commutation, the current flowing through the thyristor is forced to become
zero by external circuitry.
14. What is meant by dc chopper?
A dc chopper is a high speed static switch used to obtain variable dc voltage from
a constant dc voltage.
15. What are the applications of dc chopper?
a. Battery operated vehicles
b. Traction motor control in electric traction
c. Trolly cars
d. Marine hoists
e. Mine haulers
f. Electric braking.
16. What are the applications of dc chopper?
Chopper provides
a. High efficiency
b. Smooth acceleration
c. Fast dynamic response
d. Regeneration
17. What is meant by step-up and step-down chopper?
In a step- down chopper or Buck converter, the average output voltage is less than
the input voltage. In a step- up chopper or Boost converter, the average output voltage is
more than the input voltage.
18. Write down the expression for average output voltage for step down chopper.
Average output voltage for step down chopper V0 = _ Vs, _ is the duty cycle
19. Write down the expression for average output voltage for step up chopper.
Average output voltage for step down chopper V0 = Vs, _ is the duty cycle
1-
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20. What is meant by duty-cycle?
Duty cycle is defined as the ratio of the on time of the chopper to the total time
period of the chopper. It is denoted by .
PART-B
1. Discuss the working of 1_ two pulse bridge converter with RLE load using
relevant waveforms. (16)
2. A 1_ two pulse bridge converter feeds power to RLE load with R=6_, L= 6mH,
E = 60v, ac source voltage is 230v, 50Hz for continuous conduction. Find the
average value of load current for firing angle of 50 °. In case one of four SCR‟S
gets open circuited. Find the new value of average load current assuming the
output current as continuous. (16)
3. a) Explain the operation of 1_ semi converter and derive the expressions for its
average and rms output voltage. (8)
3. b) Derive the expressions for harmonic , displacement and power factor of a 1_ full
converter from the fundamental principle. (8)
4. Explain the working of 1_ full converter with RL load and derive the expression
for the average and rms value. (16)
UNIT-III
DC TO DC CONVERTER
1. What are the two types of control strategies?
a. Time Ratio Control (TRC)
b. Current Limit Control method (CLC)
2. What is meant by TRC?
In TRC, the value of Ton / T is varied in order to change the average output
voltage.
3. What are the two types of TRC?
a. Constant frequency control
b. Variable frequency control
4. What is meant by FM control in a dc chopper?
In frequency modulation control, the chopping frequency f (or the chopping
period T) is varied. Here two controls are possible.
a. On-time Ton is kept constant
b. Off period Toff is kept constant.
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5. What is meant by PWM control in dc chopper?
In this control method, the on time Ton is varied but chopping frequency is kept
constant. The width of the pulse is varied and hence this type of control is known as Pulse
Width Modulation (PWM).
6. Write down the expression for the average output voltage for step down and step up
chopper.
Average output voltage for step down chopper is VO = VS. Average output
voltage for step up chopper is VO = VS x [1/ ( 1- )].
7. What are the different types of chopper with respect to commutation process?
a. Voltage commutated chopper.
b. Current commutated chopper.
c. Load commutated chopper.
8. What is meant by voltage commutation?
In this process, a charged capacitor momentarily reverse biases the conducting
thyristor and turn it off.
9. What is meant by current commutation?
In this process, a current pulse is made to flow in the reverse direction through the
conducting thyristor and when the net thyristor current becomes zero, it is turned off.
10. What is meant by load commutation?
In this process, the load current flowing through the thyristor either becomes zero or
is transferred to another device from the conducting thyristor.
11. What are the advantages of current commutated chopper?
a. The capacitor always remains charged with the correct polarity.
b. Commutation is reliable as load current is less than the peak commutation current
ICP.
c. The auxiliary thyristor TA is naturally commutated as its current passes through
zero value.
12. What are the advantages of load commutated chopper?
a. Commutating inductor is not required.
b. It is capable of commutating any amount of load current.
c. It can work at high frequencies in the order of kHz.
d. Filtering requirements are minimal.
13. What are the disadvantages of load commutated chopper?
a. For high power applications, efficiency becomes very low because of high
switching losses at high operating frequencies.
b. Freewheeling diode is subjected to twice the supply voltage.
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c. Peak load voltage is equal to twice the supply voltage.
d. The commutating capacitor has to carry full load current at a frequency of half
chopping frequency.
e. One thyristor pair should be turned-on only when the other pair is commutated.
This can be realized by sensing the capacitor current that is alternating.
14. What is meant by inverter?
A device that converts dc power into ac power at desired output voltage and
frequency is called an inverter.
15. What are the applications of an inverter?
a. Adjustable speed drives
b. Induction heating
c. Stand-by aircraft power supplies
d. UPS
e. HVDC transmission
16. What are the main classification of inverter?
a. Voltage Source Inverter
b. Current Source Inverter
17. Why thyristors are not preferred for inverters?
Thyristors require extra commutation circuits for turn off which results in increased
complexity of the circuit. For these reasons thyristors are not preferred for inverters.
18. How output frequency is varied in case of a thyristor?
The output frequency is varied by varying the turn off time of the thyristors in the
inverter circuit, i.e. the delay angle of the thyristors is varied.
19. Give two advantages of CSI.
a. CSI does not require any feedback diodes.
b. Commutation circuit is simple as it involves only thyristors.
20. What is the main drawback of a single phase half bridge inverter?
It require a 3-wire dc supply.
PART – B
1. Discuss the principle of operation of DC-DC step down chopper with suitable
waveforms. Derive the expression for its average dc voltage. (16)
2. A step down dc chopper has input voltage of 230v with 10 ohm load, voltage
drop across chopper is 2v, when it is on. For a duty cycle of 0.5.
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Calculate i) average and rms value of output voltage ii) power delivered to the
load. (16)
3. Explain the two quadrant dc chopper operation with RLE load using suitable
waveforms. (16)
4. a) Explain time ratio control and current limit control strategies. (8)
b) Explain the resonant switching based SMPS. . (8)
5. Explain any one type of switched mode regulator and derive the expression
for it. (16)
UNIT-IV
INVERTERS
1. Why diodes should be connected in antiparallel with the thyristors in inverter
circuits?
For RL loads, load current will not be in phase with load voltage and the diodes
connected in anti parallel will allow the current to flow when the main thyristors are turned
off. These diodes are called feedback diodes.
2. What types of inverters require feedback diodes?
VSI with RL load.
3. What is meant a series inverter?
An inverter in which the commutating elements are connected in series with the
load is called a series inverter.
4. What is the condition to be satisfied in the selection of L and C in a series inverter?
R2 < 4L
5. What is meant a parallel inverter?
An inverter in which the commutating elements are connected in parallel with the
load is called a parallel inverter.
6. What are the applications of a series inverter?
The thyristorised series inverter produces an approximately sinusoidal waveform at a high
output frequency, ranging from 200 Hz to 100kHz. It is commonly used for fixed output
applications such as
a. Ultrasonic generator.
b. Induction heating.
c. Sonar Transmitter
d. Fluorescent lighting.
7. How is the inverter circuit classified based on commutation circuitry?
a. Line commutated inverters.
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b. Load commutated inverters.
c. Self commutated inverters.
d. Forced commutated inverters.
8. What is meant by McMurray inverter?
It is an impulse commutated inverter which relies on LC circuit and an auxiliary
thyristor for commutation in the load circuit.
9. What are the applications of a CSI?
a. Induction heating
b. Lagging VAR compensation
c. Speed control of ac motors
d. Synchronous motor starting.
10. What is meant by PWM control?
In this method, a fixed dc input voltage is given to the inverter and a controlled
ac output voltage is obtained by adjusting the on and off periods of the inverter
components. This is the most popular method of controlling the output voltage and this
method is termed as PWM control
.
11. What are the advantages of PWM control?
a. The output voltage can be obtained without any additional components.
b. Lower order harmonics can be eliminated or minimized along with its output
voltage control. As the higher order harmonics can be filtered easily, the filtering
requirements are minimized.
12. What are the disadvantages of the harmonics present in the inverter system?
a. Harmonic currents will lead to excessive heating in the induction motors. This
will reduce the load carrying capacity of the motor.
b. If the control and the regulating circuits are not properly shielded, harmonics
from power ride can affect their operation and malfunctioning can result.
c. Harmonic currents cause losses in the ac system and can even some time produce
resonance in the system. Under resonant conditions, the instrumentation and
metering can be affected.
d. On critical loads, torque pulsation produced by the harmonic current can be
useful.
13. What are the methods of reduction of harmonic content?
a. Transformer connections
b. Sinusoidal PWM
c. Multiple commutation in each cycle
d. Stepped wave inverters
14. Compare CSI and VSI.
S. No. VSI CSI
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1.Input voltage is maintained Constant
Input current is constant but adjustable
2.The output voltage does not depend on the load The output current does not
depend on the load
3.The magnitude of the output current and its waveform depends on the nature of
the load impedance The magnitude of the output voltage
and its waveform depends on the nature of the load impedance
4.It requires feedback diodes It does not requires feedback diodes
5. Commutation circuit is complicated i.e. it contains capacitors and inductors.
Commutation circuit is simple i.e. it contains only capacitors.
15. What are the disadvantages of PWM control?
SCRs are expensive as they must possess low turn-on and turn-off times.
16. What does ac voltage controller mean?
It is device which converts fixed alternating voltage into a variable voltage
without change in frequency.
17. What are the applications of ac voltage controllers?
a. Domestic and industrial heating
b. Lighting control
c. Speed control of single phase and three phase ac motors
d. Transformer tap changing
18. What are the advantages of ac voltage controllers?
a. High efficiency
b. Flexibility in control
c. Less maintenance
19. What are the disadvantages of ac voltage controllers?
The main draw back is the introduction of harmonics in the supply current and the
load voltage waveforms particularly at low output voltages
.
20. What are the two methods of control in ac voltage controllers?
a. ON-OFF control
b. Phase control
PART – B
1. Explain the operation of single phase half bridge inverter with a neat
sketch. (16)
2. The single phase half bridge inverter has resistive load of R=10 ohm and dc
input voltage is 220v. Determine rms output voltage, average value, rms
current and output power. (16)
3. Explain the operation of single phase full bridge inverter with neat
sketch. (16)
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4. The single phase full bridge inverter has resistive load of R=2.4 ohm and dc
input voltage is 48v. Determine rms output voltage at the fundamental
frequency, output power. And the total harmonic distortion. (16)
5. Describe the working of three phase inverter with suitable waveform (16)
UNIT-V
AC TO AC CONVERTERS
1. What is the difference between ON-OFF control and phase control?
ON-OFF control: In this method, the thyristors are employed as
switches to connect the load circuit to the source for a few cycles of the load voltage and
disconnect it for another few cycles. Phase control: In this method, thyristor switches
connect the load to the ac source for a portion of each half cycle of input voltage.
2. What is the advantage of ON-OFF control?
Due to zero-voltage and zero current switching of thyristors, the harmonics
generated by the switching action are reduced.
3. What is the disadvantage of ON-OFF control?
This type of control is applicable in systems that have high mechanical inertia and
high thermal time constant.
4. What is the duty cycle in ON-OFF control method?
Duty cycle K = n/ (n + m), where n = no. of ON cycles, m = no. of OFF cycles.
5. What is meant by unidirectional or half-wave ac voltage controller?
Here the power flow is controlled only during the positive half-cycle of the input
voltage.
6. What are the disadvantages of unidirectional or half-wave ac voltage controller?
a. Due to the presence of diode on the circuit, the control range is limited and the
effective RMS output voltage can be varied between 70.7% and 100%.
b. The input current and output voltage are asymmetrical and contain a dc
component. If there is an input transformer, saturation problem will occur
c. It is only used for low power resistive load.
7. What is meant by bidirectional or half-wave ac voltage controller?
Here the power flow is controlled during both cycles of the input voltage.
8. What is the control range of firing angle in ac voltage controller with RL load?
The control range is F < a <180°, where F = load power factor angle.
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9. What type of gating signal is used in single phase ac voltage controller with RL
load?
High frequency carrier gating signal is used for single phase ac voltage controller
with RL load.
10. What are the disadvantages of continuous gating signal?
a. More heating of the SCR gate.
b. Increases the size of pulse transformer.
11. What is meant by high frequency carrier gating?
Thyristor is turned on by using a train of pulses from a to p. This type of signal
is called as high frequency carrier gating.
12. What is meant by sequence control of ac voltage regulators?
It means that the stages of voltage controllers in parallel triggered in a proper
sequence one after the other so as to obtain a variable output with low harmonic content.
13. What are the advantages of sequence control of ac voltage regulators?
a. System power factor is improved.
b. Harmonics are reduced in the source current and the load voltage.
14. What is meant by cyclo-converter?
It converts input power at one frequency to output power at another frequency
with one-stage conversion. Cycloconverter is also known as frequency changer.
15. What are the two types of cyclo-converters?
a. Step-up cyclo-converters
b. Step-down cyclo-converters
16. What is meant by step-up cyclo-converters?
In these converters, the output frequency is less than the supply frequency.
17. What is meant by step-down cyclo-converters?
In these converters, the output frequency is more than the supply frequency.
18. What are the applications of cyclo-converter?
a. Induction heating
b. Speed control of high power ac drives
c. Static VAR generation
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d. Power supply in aircraft or ship boards
19. What is meant by positive converter group in a cyclo converter?
The part of the cycloconverter circuit that permits the flow of current during
Positive half cycle of output current is called positive converter group.
20. What is meant by negative converter group in a cyclo converter?
The part of the cyclo converter circuit that permits the flow of current during
negative half cycle of output current is called negative converter group.
PART-B
1. Draw the circuit diagram of 1_ capacitor commutated current source inverter
and explain its operation with equivalent circuits for different modes and
necessary waveforms.
2. Explain the operation of multistage control of AC voltage controllers with neat
diagram.
3. .Explain the operation of 1_ AC voltage controller with RL load.
4. Explain the operation of sequence control of AC voltage controller..
5. Explain the operation of 1_ sinusoidal AC voltage controller..
6. For a 1_ voltage controller, feeding a resistive load, draw the waveforms of source
voltage, gating signals, output voltage and voltage across the SCR. Describe the working
with reference to waveforms drawn.
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