A DC motor chapter is summarized in 3 sentences:
DC machines can operate as motors or generators and include DC motors which use a DC power source and have a stationary field coil and rotating armature. The speed of a DC motor is proportional to its back EMF and inversely proportional to the armature current. Examples show how to calculate the speed of DC motors under different load conditions by determining the back EMF using the motor's equivalent circuit.
This document provides an overview of DC machines, including DC motors and DC generators. It discusses:
- The basic components and construction of DC machines, including the stator, rotor, field winding, armature winding, commutator, and brushes.
- The fundamentals of how DC machines operate based on electromagnetic induction principles of generator and motor action.
- The equivalent circuits used to model DC machines, representing the armature and field circuits.
- Different types of DC motors like separately excited, shunt, series, and compound motors.
- Factors that determine the speed of DC motors like armature voltage, current, and magnetic flux.
- Examples calculating voltages,
1) DC machines operate based on the principles that voltage is induced in a conductor moving through a magnetic field (generator action) and a force is induced on a conductor with current in a magnetic field (motor action).
2) The simplest DC machine is a single loop of wire rotating through magnetic poles, which induces a voltage that can be extracted using a commutator and brushes.
3) Real DC machines have more complex windings and commutation systems to produce a DC output and overcome issues like armature reaction.
4) The main types of DC generators - separately excited, shunt, and series - have different characteristics based on how their fields are connected that determine how voltage and current vary with load
- DC machines can operate as either generators or motors. A generator produces voltage when its coil rotates through a magnetic field, while a motor produces torque on its coil when current passes through it in a magnetic field.
- The simplest DC machine is a single loop of wire rotating through magnetic poles. Induced voltage and torque depend on flux, speed/current, and construction constants.
- Real DC machines use commutators and brushes to produce DC output from the AC voltage induced in the rotor coils. Problems during commutation like sparking are reduced by techniques like interpoles.
- The internal voltage and torque equations account for flux, speed/current, and construction constants. Power losses include copper, brush,
Torque produced by a DC motor is proportional to the product of current in the armature winding (Ia) and the magnetic field flux (Φ).
The flux is produced by the current in the field winding (If).
Therefore, Torque (T) ∝ Ia × If
For different types of DC motors, the field current If is related differently to the armature current Ia.
2. Derive the Speed equation for a DC Motor.
Slides of DC Machines with detailed explanationOmer292805
This document provides an overview of DC machines, including DC motors and generators. It discusses the basic components and principles of operation for DC machines. Some key points:
- DC machines convert mechanical energy to electrical energy (generators) or vice versa (motors). They are commonly used to drive industrial loads.
- The main parts are the stator, rotor/armature, commutator, and brushes. The commutator converts the AC voltage in the rotor to DC.
- DC motors operate by applying a DC current to the armature in a magnetic field, producing a torque via the Lorentz force. Speed and torque can be regulated by controlling field and armature circuits.
-
The document describes the key components and operation of an AC generator. It includes:
- The main components are the field, armature, prime mover, rotor, stator, and slip rings. The rotor and stator can each be the field or armature depending on the generator type.
- In operation, the prime mover rotates the rotor through the stationary field, inducing voltage in the armature windings. Slip rings allow a continuous connection to the rotating armature.
- Losses occur from internal resistance, hysteresis in the iron cores, and mechanical factors like bearing friction. Efficiency is the ratio of output to input power. Generators are rated by voltage, current, power
DC motors have excellent speed and torque control characteristics and are often used to drive pumps and in transportation applications. A DC motor operates on the principle that a current-carrying conductor in a magnetic field experiences a force. It consists of a rotor that spins inside a stator. DC motors convert electrical energy into mechanical energy. The types of DC motors include shunt-wound, series-wound, and compound-wound motors, which have different characteristics related to torque, speed, and efficiency. The speed and direction of a DC motor can be controlled by varying the current in the field windings or armature. Losses include copper, iron, friction, and brush contact losses.
This document provides an overview of DC machines, including DC motors and DC generators. It discusses:
- The basic components and construction of DC machines, including the stator, rotor, field winding, armature winding, commutator, and brushes.
- The fundamentals of how DC machines operate based on electromagnetic induction principles of generator and motor action.
- The equivalent circuits used to model DC machines, representing the armature and field circuits.
- Different types of DC motors like separately excited, shunt, series, and compound motors.
- Factors that determine the speed of DC motors like armature voltage, current, and magnetic flux.
- Examples calculating voltages,
1) DC machines operate based on the principles that voltage is induced in a conductor moving through a magnetic field (generator action) and a force is induced on a conductor with current in a magnetic field (motor action).
2) The simplest DC machine is a single loop of wire rotating through magnetic poles, which induces a voltage that can be extracted using a commutator and brushes.
3) Real DC machines have more complex windings and commutation systems to produce a DC output and overcome issues like armature reaction.
4) The main types of DC generators - separately excited, shunt, and series - have different characteristics based on how their fields are connected that determine how voltage and current vary with load
- DC machines can operate as either generators or motors. A generator produces voltage when its coil rotates through a magnetic field, while a motor produces torque on its coil when current passes through it in a magnetic field.
- The simplest DC machine is a single loop of wire rotating through magnetic poles. Induced voltage and torque depend on flux, speed/current, and construction constants.
- Real DC machines use commutators and brushes to produce DC output from the AC voltage induced in the rotor coils. Problems during commutation like sparking are reduced by techniques like interpoles.
- The internal voltage and torque equations account for flux, speed/current, and construction constants. Power losses include copper, brush,
Torque produced by a DC motor is proportional to the product of current in the armature winding (Ia) and the magnetic field flux (Φ).
The flux is produced by the current in the field winding (If).
Therefore, Torque (T) ∝ Ia × If
For different types of DC motors, the field current If is related differently to the armature current Ia.
2. Derive the Speed equation for a DC Motor.
Slides of DC Machines with detailed explanationOmer292805
This document provides an overview of DC machines, including DC motors and generators. It discusses the basic components and principles of operation for DC machines. Some key points:
- DC machines convert mechanical energy to electrical energy (generators) or vice versa (motors). They are commonly used to drive industrial loads.
- The main parts are the stator, rotor/armature, commutator, and brushes. The commutator converts the AC voltage in the rotor to DC.
- DC motors operate by applying a DC current to the armature in a magnetic field, producing a torque via the Lorentz force. Speed and torque can be regulated by controlling field and armature circuits.
-
The document describes the key components and operation of an AC generator. It includes:
- The main components are the field, armature, prime mover, rotor, stator, and slip rings. The rotor and stator can each be the field or armature depending on the generator type.
- In operation, the prime mover rotates the rotor through the stationary field, inducing voltage in the armature windings. Slip rings allow a continuous connection to the rotating armature.
- Losses occur from internal resistance, hysteresis in the iron cores, and mechanical factors like bearing friction. Efficiency is the ratio of output to input power. Generators are rated by voltage, current, power
DC motors have excellent speed and torque control characteristics and are often used to drive pumps and in transportation applications. A DC motor operates on the principle that a current-carrying conductor in a magnetic field experiences a force. It consists of a rotor that spins inside a stator. DC motors convert electrical energy into mechanical energy. The types of DC motors include shunt-wound, series-wound, and compound-wound motors, which have different characteristics related to torque, speed, and efficiency. The speed and direction of a DC motor can be controlled by varying the current in the field windings or armature. Losses include copper, iron, friction, and brush contact losses.
A DC motor converts electrical energy into mechanical energy by using the interaction between a current-carrying conductor and a magnetic field. There are different types of DC motors including permanent magnet, shunt wound, series wound, and compound wound motors. The speed of a DC motor depends on the back emf generated, which is proportional to the flux and rotational speed. The torque depends on the current and flux. DC motors have characteristic curves showing the relationships between torque and current, speed and current, and speed and torque.
BEE - DC Machines basic of electronic and electrical enginnerringkavi7010764469
The document discusses the construction and working principles of DC machines. It describes how DC machines can operate as either generators or motors. As a generator, a DC machine converts mechanical energy into electrical energy via electromagnetic induction. As a motor, it converts electrical energy into mechanical torque by applying a current-carrying conductor in a magnetic field. The key components of a DC machine include an armature, commutator, field coils, and poles which allow it to generate or be driven by a DC current based on Faraday's law of induction.
Electrical Power Systems Synchronous GeneratorMubarek Kurt
Here are the steps to solve this problem:
a) Given: Generator is 6 pole, 50 Hz
Using the synchronous speed formula: nm = 120f/P
nm = 120*50/6 = 1000 RPM
b) Terminal voltage at different power factors:
1) Given load: Ia = 60 A, PF = 0.8 lagging
Using phasor diagram: Vt = Ea - IaXs
Ea = Vt + IaXs = 480 + 60*1 = 540 V
Vt = 540*cos(cos-1(0.8)) = 480 V
2) PF = 1.0
Vt = Ea = 540 V
3) PF
1. A synchronous generator produces power by inducing a 3-phase voltage in its stator windings via a rotating magnetic field created by its rotor.
2. The rotor contains field windings that are supplied with DC current to produce the magnetic field.
3. When load is applied, armature reaction causes the induced voltage to differ from the output voltage based on the load power factor.
This document describes the components and operation of a DC motor. It discusses the stator, rotor, brushes, and commutator. It explains how current flowing through the rotor interacts with the magnetic field from the stator to generate torque. The document also covers different types of DC motors including permanent magnet, series, shunt, and compound wound motors. It provides equations for torque, speed, power, EMF, and terminal voltage.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, and terminal voltage of DC motors.
- How shunt wound, series wound, and separately excited motors differ in their field and armature windings connections.
- Formulas for calculating speed, torque, induced emf, and armature current as a function of motor parameters like resistance, flux, and supply voltage.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, terminal voltage, and methods of connection for DC motors.
- How to analyze performance and calculate characteristics like torque, speed, current, and voltage for DC motors.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, terminal voltage, and methods of connection for DC motors.
- How to analyze performance and calculate characteristics like torque, speed, current, and voltage for DC motors.
This document describes the principles of operation of a 3-phase alternator. It discusses how a synchronous generator works using Faraday's law of electromagnetic induction. It also describes the different components of a 3-phase alternator including the stator, rotor, and different winding configurations. The document also discusses how varying the field current can control the output voltage of the alternator and how the number of poles and rotor speed determine the output frequency. Open and short circuit testing characteristics are also summarized.
The document discusses direct current (DC) generators, including:
1. DC generators operate by converting mechanical energy to electrical energy as conductors move through a magnetic field, inducing an electromotive force (EMF) based on Faraday's law of induction.
2. The construction of DC generators includes a yoke, rotor, stator, field electromagnets, pole cores, brushes, shaft, armature coils, commutator, and bearings. The commutator is needed to produce steady DC output from the pulsating current induced in the armature coils.
3. There are different types of DC generators including separately excited, self-excited (shunt-wound,
1. The document discusses the syllabus and basics of synchronous generators or alternators.
2. Synchronous generators convert mechanical power into electrical power through electromagnetic induction. They are used as the primary source of electrical energy in large power grids.
3. The basic parts are the rotor with field windings, and the stator with 3-phase armature windings. The frequency of the induced EMF depends on the rotor speed and number of poles.
This document provides information about experiments conducted in an electrical machines lab at Mehran University of Engineering and Technology. It includes an index listing 12 experiments conducted between August and October on topics like DC generators, motors, and control systems. Practical 1 provides an introduction to electrical machine equipment like DC motors, generators, transformers, and control panels. It describes the components and operating principles. The document also includes circuit diagrams, readings tables and conclusions from experiments verifying open circuit characteristics of separately excited DC generators and self-excited series DC generators.
The document discusses the basics of DC motors and generators. It covers topics like:
- The operating principles of DC machines and how they work as motors and generators.
- Fleming's left and right hand rules for determining the direction of motion, induced voltage, and magnetic fields.
- Components of DC machines like the armature, commutator, field windings.
- How armature reaction affects the magnetic field and how it can be minimized.
- Deriving equations for the induced voltage and electromagnetic torque in DC machines.
- Characteristics and speed control methods for separately excited, series, and shunt DC motors.
The document discusses the basics of DC motors and generators. It covers topics like:
- The operating principles of DC machines and how they work as motors and generators.
- Fleming's left and right hand rules for determining the direction of motion, induced voltage, and magnetic fields.
- Components of DC machines like the armature, field coils, commutators, and different winding configurations.
- How voltage, current, torque, speed and power are related in DC motors and generators based on the magnetic flux and field excitation.
- Different types of DC machines like separately excited, shunt, series and compound motors/generators.
- Speed control methods and torque-speed characteristics of DC
A DC motor converts electrical energy into mechanical energy by using the interaction between a current-carrying conductor and a magnetic field. There are different types of DC motors including permanent magnet, shunt wound, series wound, and compound wound motors. The speed of a DC motor depends on the back emf generated, which is proportional to the flux and rotational speed. The torque depends on the current and flux. DC motors have characteristic curves showing the relationships between torque and current, speed and current, and speed and torque.
BEE - DC Machines basic of electronic and electrical enginnerringkavi7010764469
The document discusses the construction and working principles of DC machines. It describes how DC machines can operate as either generators or motors. As a generator, a DC machine converts mechanical energy into electrical energy via electromagnetic induction. As a motor, it converts electrical energy into mechanical torque by applying a current-carrying conductor in a magnetic field. The key components of a DC machine include an armature, commutator, field coils, and poles which allow it to generate or be driven by a DC current based on Faraday's law of induction.
Electrical Power Systems Synchronous GeneratorMubarek Kurt
Here are the steps to solve this problem:
a) Given: Generator is 6 pole, 50 Hz
Using the synchronous speed formula: nm = 120f/P
nm = 120*50/6 = 1000 RPM
b) Terminal voltage at different power factors:
1) Given load: Ia = 60 A, PF = 0.8 lagging
Using phasor diagram: Vt = Ea - IaXs
Ea = Vt + IaXs = 480 + 60*1 = 540 V
Vt = 540*cos(cos-1(0.8)) = 480 V
2) PF = 1.0
Vt = Ea = 540 V
3) PF
1. A synchronous generator produces power by inducing a 3-phase voltage in its stator windings via a rotating magnetic field created by its rotor.
2. The rotor contains field windings that are supplied with DC current to produce the magnetic field.
3. When load is applied, armature reaction causes the induced voltage to differ from the output voltage based on the load power factor.
This document describes the components and operation of a DC motor. It discusses the stator, rotor, brushes, and commutator. It explains how current flowing through the rotor interacts with the magnetic field from the stator to generate torque. The document also covers different types of DC motors including permanent magnet, series, shunt, and compound wound motors. It provides equations for torque, speed, power, EMF, and terminal voltage.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, and terminal voltage of DC motors.
- How shunt wound, series wound, and separately excited motors differ in their field and armature windings connections.
- Formulas for calculating speed, torque, induced emf, and armature current as a function of motor parameters like resistance, flux, and supply voltage.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, terminal voltage, and methods of connection for DC motors.
- How to analyze performance and calculate characteristics like torque, speed, current, and voltage for DC motors.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited and their characteristics.
- The principles of operation, construction, and torque-speed characteristics of DC motors.
- How to calculate torque, speed, induced emf, and other parameters for DC motors.
- Applications of the different DC motor types.
- Circuit diagrams and equations for analyzing DC motor performance.
This document provides information about direct current (DC) motors, including:
- The three main types of DC motors: shunt wound, series wound, and separately excited.
- How to calculate torque-speed characteristics for each type.
- The construction, principle of operation, induced electromotive force (emf), torque, terminal voltage, and methods of connection for DC motors.
- How to analyze performance and calculate characteristics like torque, speed, current, and voltage for DC motors.
This document describes the principles of operation of a 3-phase alternator. It discusses how a synchronous generator works using Faraday's law of electromagnetic induction. It also describes the different components of a 3-phase alternator including the stator, rotor, and different winding configurations. The document also discusses how varying the field current can control the output voltage of the alternator and how the number of poles and rotor speed determine the output frequency. Open and short circuit testing characteristics are also summarized.
The document discusses direct current (DC) generators, including:
1. DC generators operate by converting mechanical energy to electrical energy as conductors move through a magnetic field, inducing an electromotive force (EMF) based on Faraday's law of induction.
2. The construction of DC generators includes a yoke, rotor, stator, field electromagnets, pole cores, brushes, shaft, armature coils, commutator, and bearings. The commutator is needed to produce steady DC output from the pulsating current induced in the armature coils.
3. There are different types of DC generators including separately excited, self-excited (shunt-wound,
1. The document discusses the syllabus and basics of synchronous generators or alternators.
2. Synchronous generators convert mechanical power into electrical power through electromagnetic induction. They are used as the primary source of electrical energy in large power grids.
3. The basic parts are the rotor with field windings, and the stator with 3-phase armature windings. The frequency of the induced EMF depends on the rotor speed and number of poles.
This document provides information about experiments conducted in an electrical machines lab at Mehran University of Engineering and Technology. It includes an index listing 12 experiments conducted between August and October on topics like DC generators, motors, and control systems. Practical 1 provides an introduction to electrical machine equipment like DC motors, generators, transformers, and control panels. It describes the components and operating principles. The document also includes circuit diagrams, readings tables and conclusions from experiments verifying open circuit characteristics of separately excited DC generators and self-excited series DC generators.
The document discusses the basics of DC motors and generators. It covers topics like:
- The operating principles of DC machines and how they work as motors and generators.
- Fleming's left and right hand rules for determining the direction of motion, induced voltage, and magnetic fields.
- Components of DC machines like the armature, commutator, field windings.
- How armature reaction affects the magnetic field and how it can be minimized.
- Deriving equations for the induced voltage and electromagnetic torque in DC machines.
- Characteristics and speed control methods for separately excited, series, and shunt DC motors.
The document discusses the basics of DC motors and generators. It covers topics like:
- The operating principles of DC machines and how they work as motors and generators.
- Fleming's left and right hand rules for determining the direction of motion, induced voltage, and magnetic fields.
- Components of DC machines like the armature, field coils, commutators, and different winding configurations.
- How voltage, current, torque, speed and power are related in DC motors and generators based on the magnetic flux and field excitation.
- Different types of DC machines like separately excited, shunt, series and compound motors/generators.
- Speed control methods and torque-speed characteristics of DC
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2. Introduction
• An electrical machine is link between an electrical
system and a mechanical system.
• Conversion from mechanical to electrical: generator
• Conversion from electrical to mechanical: motor
3. Introduction
Machines are called
• AC machines (generators or motors) if the electrical
system is AC.
• DC machines (generators or motors) if the
electrical system is DC.
4. DC machines can be divide by:
a) DC motor
b) DC Generator
DC Machines
DC Motor DC Generator
9. DC Machines Fundamentals
• Stator: is the stationary part of the machine. The
stator carries a field winding that is used to
produce the required magnetic field by DC
excitation.
• Rotor (Armature): is the rotating part of the
machine. The rotor carries a distributed winding,
and is the winding where the e.m.f. is induced.
• Field winding: Is wound on the stator poles to
produce magnetic field (flux) in the air gap.
• Armature winding: Is composed of coils placed in
the armature slots.
• Commutator: Is composed of copper bars,
insulated from each other. The armature winding is
connected to the commutator.
• Brush: Is placed against the commutator surface.
Brush is used to connect the armature winding to
external circuit through commutator
10. DC Machines Fundamentals
In DC machines, conversion of energy from electrical to mechanical
form or vice versa results from the following two electromagnetic
phenomena
1.When a conductor moves in a magnetic field, voltage is induced in
the conductor.
2. When a current carrying conductor is placed in magnetic field, the
conductor experiences a mechanical forces.
11. DC Machines Fundamentals
Generator action:
An e.m.f. (voltage) is induced in a conductor if it
moves through a magnetic field.
Motor action:
A force is induced in a conductor that has a current
going through it and placed in a magnetic field
•Any DC machine can act either as a generator or
as a motor.
12. DC Machines Equivalent Circuit
The equivalent circuit of DC machines has two
components:
Armature circuit:
• It can be represented by a voltage source and a
resistance connected in series (the armature
resistance). The armature winding has a
resistance, RA.
The field circuit:
• It is represented by a winding that generates the
magnetic field and a resistance connected in
series. The field winding has resistance RF.
14. • In a dc motor, the stator poles
are supplied by dc excitation
current, which produces a dc
magnetic field.
• The rotor is supplied by dc
current through the brushes,
commutator and coils.
• The interaction of the
magnetic field and rotor
current generates a force that
drives the motor.
Basic Operation of DC Motor
15. • The magnetic field lines enter into
the rotor from the north pole (N)
and exit toward the south pole (S)
• The poles generate a magnetic
field that is perpendicular to the
current carrying conductors
• The interaction between the field
and the current produces a
Lorentz force
• The force is perpendicular to both
the magnetic field and conductor
Basic Operation of DC Motor
16. Basic Operation of DC Motor
• The generated force turns the
rotor until the coil reaches the
neutral point between the poles.
• At this point, the magnetic field
becomes practically zero
together with the force.
• However, inertia drives the motor
beyond the neutral zone where
the direction of the magnetic field
reverses.
• To avoid the reversal of the force
direction, the commutator
changes the current direction,
which maintains the counter
clockwise rotation.
17. • Before reaching the neutral
zone, the current enters in
segment 1 and exits from
segment 2
• Therefore, current enters the coil
end at slot ‘a’ and exits from slot
‘b’ during this stage
• After passing the neutral zone,
the current enters segment 2 and
exits from segment 1,
• This reverses the current
direction through the rotor coil,
when the coil passes the neutral
zone
• The result of this current reversal
is the maintenance of the
rotation
Basic Operation of DC Motor
19. Classification of DC Motor
1. Separately Excited DC Motor
• Field and armature windings are either connected
separate.
2. Shunt DC Motor
• Field and armature windings are either connected in
parallel.
3. Series DC Motor
• Field and armature windings are connected in
series.
4. Compound DC Motor
• Has both shunt and series field so it combines
features of series and shunt motors.
20. Important terms
• VT – supply voltage
• EA – internal generated voltage/back e.m.f.
• RA – armature resistance
• RF – field/shunt resistance
• RS – series resistance
• IL – load current
• IF – field current
• IA – armature current
• IL – load current
• n – speed
21. Generated or back e.m.f. of DC
Motor
• General form of back e.m.f.,
Φ = flux/pole (Weber)
Z = total number of armature conductors
= number of slots x number of conductor/slot
P = number of poles
A = number of parallel paths in armature
[A = 2 (for wave winding), A = P (for lap winding)]
N = armature rotation (rpm)
EA = back e.m.f.
A
P
ZN
EA
60
22. Torque Equation of a DC Motor
• The armature torque of a DC motor is given by
Φ = flux/pole (Weber)
Z = total number of armature conductors
= number of slots x number of conductor/slot
P = number of poles
A = number of parallel paths in armature
IA = armature current
Ta = armature torque
)
(
2
meter
Newton
A
P
ZI
T A
a
23. Equivalent Circuit of DC Motor
F
T
F
R
V
I
A
A
A
T R
I
E
V
F
F
F
R
V
I
A
A
A
T R
I
E
V
A
L I
I
Separately Excited DC Motor
Shunt DC Motor
F
A
L I
I
I
24. )
( S
A
A
A
T R
R
I
E
V
L
S
A I
I
I
Series DC Motor
)
( S
A
A
A
T R
R
I
E
V
F
T
F
R
V
I F
L
A I
I
I
Compound DC Motor
25. Speed of a DC Motor
• For shunt motor
• For series motor
1
2
1
2
1
2
2
1
1
2
1
2
,
A
A
A
A
E
E
n
n
then
If
E
E
n
n
2
1
1
2
2
1
1
2
1
2
A
A
A
A
A
A
I
I
E
E
E
E
n
n
26. Example 1
A 250 V, DC shunt motor takes a line
current of 20 A. Resistance of shunt
field winding is 200 Ω and resistance of
the armature is 0.3 Ω. Find the
armature current, IA and the back e.m.f.,
EA.
27. Solution
Given quantities:
• Terminal voltage, VT = 250 V
• Field resistance, RF = 200 Ω
• Armature resistance, RA = 0.3 Ω
• Line current, IL = 20 A
Figure 1
28. Solution (cont..)
the field current,
the armature current,
VT = EA + IARA
the back e.m.f.,
EA = VT – IARA = 250 V – (18.75)(0.3) = 244.375 V
A
25
.
1
200
V
250
F
T
F
F
A
L
R
V
I
I
I
I
18.75A
A
25
.
1
A
20
F
L
A I
I
I
29. Example 2
A 50hp, 250 V, 1200 r/min dc shunt motor
with compensating windings has an
armature resistance (including the
brushes, compensating windings, and
interpoles) of 0.06 Ω. Its field circuit has a
total resistance Radj + RF of 50 Ω, which
produces a no-load speed of 1200 r/min.
There are 1200 turns per pole on the
shunt field winding.
30. Example 2 (cont..)
a) Find the speed of this motor when its
input current is 100 A.
b) Find the speed of this motor when its
input current is 200 A.
c) Find the speed of this motor when its
input current is 300 A.
31. Solution
Given quantities:
• Terminal voltage, VT = 250 V
• Field resistance, RF = 50 Ω
• Armature resistance, RA = 0.06 Ω
• Initial speed, n1 = 1200 r/min
Figure 2
32. Solution (cont..)
(a) When the input current is 100A, the armature
current in the motor is
Therefore, EA at the load will be
A
95
A
5
A
100
50
V
250
A
100
F
T
L
F
L
A
R
V
I
I
I
I
V
3
.
244
V
7
.
5
V
250
)
06
.
0
)(
A
95
(
V
250
A
A
T
A R
I
V
E
33. Solution (cont..)
• The resulting speed of this motor is
min
/
r
1173
min
/
r
1200
250
3
.
244
1
1
2
2
1
2
1
2
V
V
n
E
E
n
E
E
n
n
A
A
A
A
34. Solution (cont..)
(b) When the input current is 200A, the armature
current in the motor is
Therefore, EA at the load will be
A
195
A
5
A
200
50
V
250
A
200
F
T
L
F
L
A
R
V
I
I
I
I
V
3
.
238
V
7
.
11
V
250
)
06
.
0
)(
195
(
V
250
A
R
I
V
E A
A
T
A
35. Solution (cont..)
• The resulting speed of this motor is
min
/
r
1144
min
/
r
1200
250
3
.
238
1
1
2
2
1
2
1
2
V
V
n
E
E
n
E
E
n
n
A
A
A
A
36. Solution (cont..)
(c) When the input current is 300A, the armature
current in the motor is
Therefore, EA at the load will be
A
295
A
5
A
300
50
V
250
A
300
F
T
L
F
L
A
R
V
I
I
I
I
V
3
.
232
V
7
.
17
V
250
)
06
.
0
)(
295
(
V
250
A
R
I
V
E A
A
T
A
37. Solution (cont..)
• The resulting speed of this motor is
min
/
r
1115
min
/
r
1200
V
250
V
3
.
232
1
1
2
2
1
2
1
2
n
E
E
n
E
E
n
n
A
A
A
A
38. Example 3
The motor in Example 2 is now connected in
separately excited circuit as shown in Figure 3.
The motor is initially running at speed, n = 1103
r/min with VA = 250 V and IA = 120 A, while
supplying a constant-torque load. If VA is reduced
to 200 V, determine
i). the internal generated voltage, EA
ii). the final speed of this motor, n2
40. Solution
Given quantities
• Initial line current, IL = IA = 120 A
• Initial armature voltage, VA = 250 V
• Armature resistance, RA = 0.06 Ω
• Initial speed, n1 = 1103 r/min
41. Solution (cont..)
i) The internal generated voltage
EA = VT - IARA
= 250 V – (120 A)(0.06 Ω)
= 250 V – 7.2 V
= 242.8 V
42. Solution (cont..)
ii) Use KVL to find EA2
EA2 = VT - IA2RA
Since the torque is constant ant he flux is constant,
IA is constant. This yields a voltage of
EA2 = 200 V – (120 A)(0.06 Ω)
= 200 V – 7.2 V
= 192.8 V
43. Solution (cont..)
• The final speed of this motor
min
/
r
876
min
/
r
1103
V
8
.
242
V
8
.
192
1
1
2
2
1
2
1
2
n
E
E
n
E
E
n
n
A
A
A
A
44. Example 4
A DC series motor is running with a speed
of 800 r/min while taking a current of 20 A
from the supply. If the load is changed
such that the current drawn by the motor
is increased to 50 A, calculate the speed
of the motor on new load. The armature
and series field winding resistances are
0.2 Ω and 0.3 Ω respectively. Assume the
flux produced is proportional to the
current. Assume supply voltage as 250 V.
45. Solution
Given quantities
• Supply voltage, VT = 250 V
• Armature resistance, RA = 0.2 Ω
• Series resistance, RS = 0.3 Ω
• Initial speed, n1 = 800 r/min
• Initial armature current, Ia1 = IL1 = 20 A
Figure 4
46. Solution (cont..)
For initial load, the armature current, Ia1 = 20 A and
the speed n1 = 800 r/min
V = EA1 + Ia1 (RA + RS)
The back e.m.f. at initial speed
EA1 = V - Ia1 (RA + RS)
= 250 – 20(0.2 + 0.3)
= 240 V
47. Solution (cont..)
When the armature current increased, Ia2 = 50 A, the
back emf
EA2 = V – Ia2 (RA + RS)
= 250 – 50(0.2 + 0.3)
= 225 V
min
/
r
300
50
20
240
225
800
2
1
1
2
1
2
2
1
1
2
1
2
2
1
1
2
1
2
I
I
E
E
n
n
I
I
E
E
n
n
E
E
n
n
A
A
A
A
A
A
The speed of the motor on new load
49. Generating of an AC Voltage
• The voltage generated
in any dc generator
inherently alternating
and only becomes dc
after it has been rectified
by the commutator
51. Armature windings
• The armature windings are usually former-
wound. This are first wound in the form of flat
rectangular coils and are then puller.
• Various conductors of the coils are insulated
each other. The conductors are placed in the
armature slots which are lined with tough
insulating material.
• This slot insulation is folded over above the
armature conductors placed in the slot and is
secured in place by special hard wooden or fiber
wedges.
52. Lap and wave Windings
There are two types of windings mostly
employed:
• Lap winding
• Wave winding
The difference between the two is merely
due to the different arrangement of the end
connection at the front or commutator end of
armature.
53. Generated or back e.m.f. of DC
Generator
• General form of generated e.m.f.,
Φ = flux/pole (Weber)
Z = total number of armature conductors
= number of slots x number of conductor/slot
P = number of poles
A = number of parallel paths in armature
[A = 2 (for wave winding), A = P (for lap winding)]
N = armature rotation (rpm)
E = e.m.f. induced in any parallel path in armature
A
P
ZN
E
60
54. Classification of DC Generator
1. Separately Excited DC Generator
• Field and armature windings are either connected
separate.
2. Shunt DC Generator
• Field and armature windings are either connected in
parallel.
3. Series DC Generator
• Field and armature windings are connected in
series.
4. Compound DC Generator
• Has both shunt and series field so it combines
features of series and shunt motors.
55. Equivalent circuit of DC generator
F
A
L I
I
I
A
L I
I
Separately excited DC generator
F
F
F
R
V
I
A
A
A
T R
I
E
V
Shunt DC generator
F
T
F
R
V
I
A
A
A
T R
I
E
V
56. F
A
L I
I
I
A
S
L I
I
I
Series DC generator
)
( S
A
A
A
T R
R
I
E
V
Compound DC generator
F
T
F
R
V
I
A
A
A
T R
I
E
V
57. Example
• A DC shunt generator
has shunt field winding
resistance of 100Ω. It
is supplying a load of
5kW at a voltage of
250V. If its armature
resistance is 0.02Ω,
calculate the induced
e.m.f. of the generator.
58. Solution
Given quantities
• Terminal voltage, VT = 250V
• Field resistance, RF = 100Ω
• Armature resistance, RA = 0.22Ω
• Power at the load, P = 5kW