This document describes a patent for a mechanical current converter (contact rectifier) with commutating reactors. The key aspects are that each reactor can be divided into two or more partial reactors that can be connected in series or parallel to vary the effective reactance. This allows the step current of the reactors to remain constant even if the supply voltage decreases, improving efficiency. The invention is particularly useful for plants that often operate at voltages lower than their nominal voltage.
Equal Switching Distribution Method for Multi-Level Cascaded Inverterijsrd.com
the paper proposes a new method of equal switching distribution that can be applied to cascaded multilevel inverters. This method is based on the fact that in the cascaded multilevel inverters, the output phase voltage is the sum of voltage waveforms produced by all cascaded cells. By periodically exchanging cells' voltage waveforms, the proposed method ensures equal average switching's distribution between all cascaded cells. This method is applied to the 13-level inverter, which consists of three cascaded 5-level H-bridge cells per phase. However, the proposed method can be extended to any desired number of voltage levels and applied to any type of cascaded multilevel inverter. Extensive simulation results of the tested 13- level inverter with the equal switching distribution are presented. Moreover, the proposed method is compared to the standard control approaches and its advantages are shown.
Multilevel inverters have become more popular over the years in electric high power application
with the promise of less disturbances and the possibility to function at lower switching frequencies than
ordinary two-level inverters. This paper presents information about several multilevel inverter topologies,
such as the Neutral-Point Clamped Inverter and the Cascaded Multi cell Inverter. These multilevel
inverters will also be compared with two-level inverters in simulations to investigate the advantages of
using multilevel inverters. Modulation strategies, component comparison and solutions to the multilevel
voltage source balancing problem will also be presented in this work.
Keywords — multilevel, Neutral-clamped, PWM.
Equal Switching Distribution Method for Multi-Level Cascaded Inverterijsrd.com
the paper proposes a new method of equal switching distribution that can be applied to cascaded multilevel inverters. This method is based on the fact that in the cascaded multilevel inverters, the output phase voltage is the sum of voltage waveforms produced by all cascaded cells. By periodically exchanging cells' voltage waveforms, the proposed method ensures equal average switching's distribution between all cascaded cells. This method is applied to the 13-level inverter, which consists of three cascaded 5-level H-bridge cells per phase. However, the proposed method can be extended to any desired number of voltage levels and applied to any type of cascaded multilevel inverter. Extensive simulation results of the tested 13- level inverter with the equal switching distribution are presented. Moreover, the proposed method is compared to the standard control approaches and its advantages are shown.
Multilevel inverters have become more popular over the years in electric high power application
with the promise of less disturbances and the possibility to function at lower switching frequencies than
ordinary two-level inverters. This paper presents information about several multilevel inverter topologies,
such as the Neutral-Point Clamped Inverter and the Cascaded Multi cell Inverter. These multilevel
inverters will also be compared with two-level inverters in simulations to investigate the advantages of
using multilevel inverters. Modulation strategies, component comparison and solutions to the multilevel
voltage source balancing problem will also be presented in this work.
Keywords — multilevel, Neutral-clamped, PWM.
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
This presentation explains completely about transformer. This is more important for Electrical Engineering students and all technical knowledge aspirants. I worked out in a manner to craft out a best presentation on Transformers. I hope you like it.
Space Vector Pulse Width Modulation Technique Applied to Two Level Voltage So...Qusai Abdelrahman
Space vector pulse width modulation SVPWM provides a better technique compared to the other pulse width modulation techniques. This paper presents simulation and implementation of SVPWM signal generation for driving three phase two level voltage source inverter VSI, also proposes and analyzes a new switching sequence for generating an SVPWM. Simulation results are obtained using the simulation package PSIM. and the inverter performance is evaluated in terms of total harmonic distortion (THD). The model is experimentally implemented and verified on Arduino Mega Atmega2560 microcontroller.
A Novel Transient Current Limiter Based on Three-Phase Thyristor Bridge for Y...IJPEDS-IAES
The transformer in flux current may be a transient current that happens in
electrical devices has been charged. This current depends on completely
different parameters probably the voltage magnitude, the switching on angle
the permanent flux, the core physical phemeon characteristics, the primary
circuit resistance, etc. To beat the issues arising owing to transients, these are
required to be suppressed.In this paper, an easy and economical techniquie is
conferred to limit the transient current of the Y-yg transformers. One
amongst the most benefit of this technique is it doesn’t would like any
negative feedback circuit or activity unit. The tactic relies on a three-phase
thyristors bridge single RL reactor with the individual phases of electrical
device. Since the amount of thyristors is reduced, the voltage ripple,
electrical losses and therefore the malfunction likelihood due to device
failure is reduced significantly. The projected technique has been simulated
by MATLAB simulation. It’s shown that the projected method is a lot of
economical for the transient current limitation of Y-yg transformers.
This paper presents a MATLAB/SIMULINK model of two multi-level inverter topologies. Algorithms based on space vector modulation (SVM) technique are developed in order to conduct a comparative study on diode clamped five and seven level inverters. The scheme used to develop these control algorithms are based on symmetrical sequence because of the symmetry of the switching wave. Both topologies are simulated and analyzed using a squirrel cage induction motor. The results have showed that the best motor dynamic response with less harmonic distortion and torque fluctuations is obtained when seven-level inverter is employed.
Comparison of Conventional Converter with Three-Phase Single- Stage Ac-Dc PWM...IJERA Editor
The main objective of this concept is to examine the operation of fundamental buck-based three-phase singlestage
ac–dc full-bridge converters. In this concept, the operation of this fundamental converter is explained and
analyzed, and a procedure for the design of its key components is derived and demonstrated with an example
and general concluding remarks comparing Buck-Based and Boost Based three Phase single-stage AC to DC
full Bridge converters are made.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
Analysis of on Load Tap Changing Transformer for Substationijtsrd
On load tap changing transformers play important roles in any modern power system since they allow voltages to be maintained at desired levels despite load changes. Traditionally, on load tap changer is a complex mechanical device, which has some deficiencies. On load tap changer of a transformer is presented, which can eliminate excessive conduction losses and suppress the arcing in the diverter switch, which is inherent in traditional on load transformer tap changers. The OLTC provides uninterrupted voltage is regulation of transformers under load. The transformer is equipped with a tapped winding whose tappings are connected with the tap selector of the OLTC. Most of the current commercially available automatic voltage regulators, just measure the low voltage side of the power transformer in order to control OLTC position. In this to improve tap changer control in order to perform properly also during a stressed situation in the 230 33 kV regulating power transformer for the substation. Zin Wah Aung | Aung Thike "Analysis of on Load Tap Changing Transformer for Substation" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26556.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/26556/analysis-of-on-load-tap-changing-transformer-for-substation/zin-wah-aung
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
This presentation explains completely about transformer. This is more important for Electrical Engineering students and all technical knowledge aspirants. I worked out in a manner to craft out a best presentation on Transformers. I hope you like it.
Space Vector Pulse Width Modulation Technique Applied to Two Level Voltage So...Qusai Abdelrahman
Space vector pulse width modulation SVPWM provides a better technique compared to the other pulse width modulation techniques. This paper presents simulation and implementation of SVPWM signal generation for driving three phase two level voltage source inverter VSI, also proposes and analyzes a new switching sequence for generating an SVPWM. Simulation results are obtained using the simulation package PSIM. and the inverter performance is evaluated in terms of total harmonic distortion (THD). The model is experimentally implemented and verified on Arduino Mega Atmega2560 microcontroller.
A Novel Transient Current Limiter Based on Three-Phase Thyristor Bridge for Y...IJPEDS-IAES
The transformer in flux current may be a transient current that happens in
electrical devices has been charged. This current depends on completely
different parameters probably the voltage magnitude, the switching on angle
the permanent flux, the core physical phemeon characteristics, the primary
circuit resistance, etc. To beat the issues arising owing to transients, these are
required to be suppressed.In this paper, an easy and economical techniquie is
conferred to limit the transient current of the Y-yg transformers. One
amongst the most benefit of this technique is it doesn’t would like any
negative feedback circuit or activity unit. The tactic relies on a three-phase
thyristors bridge single RL reactor with the individual phases of electrical
device. Since the amount of thyristors is reduced, the voltage ripple,
electrical losses and therefore the malfunction likelihood due to device
failure is reduced significantly. The projected technique has been simulated
by MATLAB simulation. It’s shown that the projected method is a lot of
economical for the transient current limitation of Y-yg transformers.
This paper presents a MATLAB/SIMULINK model of two multi-level inverter topologies. Algorithms based on space vector modulation (SVM) technique are developed in order to conduct a comparative study on diode clamped five and seven level inverters. The scheme used to develop these control algorithms are based on symmetrical sequence because of the symmetry of the switching wave. Both topologies are simulated and analyzed using a squirrel cage induction motor. The results have showed that the best motor dynamic response with less harmonic distortion and torque fluctuations is obtained when seven-level inverter is employed.
Comparison of Conventional Converter with Three-Phase Single- Stage Ac-Dc PWM...IJERA Editor
The main objective of this concept is to examine the operation of fundamental buck-based three-phase singlestage
ac–dc full-bridge converters. In this concept, the operation of this fundamental converter is explained and
analyzed, and a procedure for the design of its key components is derived and demonstrated with an example
and general concluding remarks comparing Buck-Based and Boost Based three Phase single-stage AC to DC
full Bridge converters are made.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
Analysis of on Load Tap Changing Transformer for Substationijtsrd
On load tap changing transformers play important roles in any modern power system since they allow voltages to be maintained at desired levels despite load changes. Traditionally, on load tap changer is a complex mechanical device, which has some deficiencies. On load tap changer of a transformer is presented, which can eliminate excessive conduction losses and suppress the arcing in the diverter switch, which is inherent in traditional on load transformer tap changers. The OLTC provides uninterrupted voltage is regulation of transformers under load. The transformer is equipped with a tapped winding whose tappings are connected with the tap selector of the OLTC. Most of the current commercially available automatic voltage regulators, just measure the low voltage side of the power transformer in order to control OLTC position. In this to improve tap changer control in order to perform properly also during a stressed situation in the 230 33 kV regulating power transformer for the substation. Zin Wah Aung | Aung Thike "Analysis of on Load Tap Changing Transformer for Substation" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26556.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/26556/analysis-of-on-load-tap-changing-transformer-for-substation/zin-wah-aung
This sermon will consider the two strongest arguments for God's Existence, The Argument from Design (Teleological Argument) and the Moral Argument. We will consider the fine tuning of the universe and complexity of biological systems as evidence of Intelligent Design. We will also consider the Moral Argument, rejecting notions that morality is somehow expressed genetically or through sheer reason and demonstrating that Christian morality is not capriciously prescriptivist, but flows from God's character organically.
International Journal of Engineering and Science Research. It is a international journal publishing high-quality articles dedicated to all aspects of engineering. IJESR is to publish peer reviewed research and review articles. fastly without delay in the developing field of engineering and science Research.
To overcome the problem of mismatched voltage levels between parallel-connected low voltage photovoltaic (PV)
arrays and the higher grid voltage, a hybrid boost three level dc-dc converter is developed based on three level inverter with
the traditional single phase diode clamping. Only one inductor, two capacitors in series, and those power switches and diodes,
which are easy to be integrated, are used for establish the topology with transformerless high voltage gain. The operation
principle of the topology is analyzed, and then the pulse width modulation (PWM) control method is obtained according to
the switching functions about the output pulse voltages of both half-bridges. Therefore, the converter can not only operate
with high voltage gain, but also make the duty cycles of power switches closer to 0.5. A feedforward closed loop control
operation is proposed such that even in varying input the converter is capable of giving a constant output. Finally an
experimental is set up in the laboratory for open loop control operation. All experimental results verify the feasibility of the
circuit and validity of the PWM control method.
AC - AC power conversions were traditionally done by using thyristor power controllers, phase angle control or by
integral cycle control, but had low PF and other disadvantages. Variable voltage, variable frequency high power conversions
are nowadays use DC link and Matrix converters, with higher efficiency and better regulation. But in situations where only
voltage regulation is required and the circuit need to be simple and less complicated, directed PWM AC-AC converters are
more preferred, due to reduced size and components. This project presents the design and simulation of a new type of AC-AC
converter which can operate as traditional non-inverting buck and boost converters, and inverting buck-boost converter as
well. This converter uses six unidirectional current flowing and bidirectional voltage blocking switches, implemented by six
reverse blocking IGBTs or series MOSFET-diode pairs, two input and output filter capacitors, and one inductor. It has no
shoot-through problem of voltage source (or capacitor) even when all switches are turned-on and therefore; PWM dead times
are not needed resulting in high quality waveforms, and solves the commutation problem without using bulky and lossy RC
snubbers or dedicated soft-commutation strategies. It has smaller switching losses because; only two switches out of six are
switched at high frequency during each half cycle of input voltage, and it can use power MOSFETs as body diode never
conducts, making it immune from MOSFET failure risk..
Fpga implementation of race control algorithm for full bridge prcp convertereSAT Journals
Abstract In this paper, the unedited race-control algorithm (RCA) for the full-bridge passive resonant commutated poles (FB-PRCP) converter is presented and implemented in cost effective field programmable gate-array. It compensates the drawbacks of that topology that are related to the slow dynamics of the auxiliary poles which are necessary to obtain zero-voltage transitions both at turn-on and turn-off conditions and makes possible its use in more general welding applications, such as manual metal arc welding, in which very fast responses are required. The proposed RCA is a simple variation of the traditional phase-shift technique, which leads to significant efficiency improvements. The guiding idea is to apply the phase-shift technique to both legs of the converter, contrarily to what has been done to date. The limitation in dynamics of the converter is completely eliminated and it gains much more readiness. The effectiveness of the RCA has been verified in simulation and it can be experimentally tested on a true converter..
Fpga implementation of race control algorithm for full bridge prcp convertereSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Development of a Novel Three Phase Grid-Tied Multilevel Inverter TopologyIAES-IJPEDS
The conventional line-commutated ac-to-dc converters/ inverters have square-shaped line current. It contains higher-order harmonics which generates EMI and it causes more heating of the core of distribution or power transformers. PWM based inverters using MOSFET/IGBT have higher switching losses, and the power handling capability and reliability are quite low in comparison to thyristors/ SCR. A thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal voltage output or waveform with low harmonic contents is most desirable for ac load using dc to ac conversion. This paper presents a new multilevel inverter topology in which three phase ac- to-dc converter circuits are used in inversion mode by controlling the switching angle. Due to natural commutation, no separate circuit is required for synchronization. In this paper simulation and analysis are done for grid-tied three-phase 6-pulse, Two three-phase, 3-pulse and 12-pulse converter. These converters are analysed for different battery voltage and different switching angle combinations in order to reduce the total harmonic distortion (THD). Three-phase harmonic filters are further added to the grid side to reduce the harmonic content in the line current. A comparative study of these converters is also presented in this paper.
SIMULATION ANALYSIS OF CLOSED LOOP DUAL INDUCTOR CURRENT-FED PUSH-PULL CONVER...Journal For Research
The current electronic devices require DC power source, which is taken from a battery or DC power supply. DC-DC converter is utilized to get regulated dc voltage from unregulated one. Switched mode power supply (SMPS) are commonly used in industrial applications, because of more advantages compared to linear power supply. In SMPS we have isolated and non-isolated converters, where isolated converters are frequently used, in order to get more voltage with multiple outputs. So among different isolated converters, push-pull converter is chosen for micro converter applications to obtain high voltage conversion ratio by using HF transformer, due to their better utilization of transformer. New methodology of control is implemented for making ZVS and ZCS at same time and to reduce the number of switches in the secondary side of dual inductor CFPP converter, which is a voltage doubler circuit. This becomes the solution for problem identification. Thus this converter with soft-switching reduces the switching losses.The current-fed push-pull converters are used in many applications like photo-voltaic (PV) power converters for boosting the output voltage. Push-pull converter is chosen for micro converter applications, to obtain high voltage conversion ratio by using high frequency (HF) transformer, due to their better utilization of transformer. This deals with the design of dual inductor CFPP converter, where zero voltage switching (ZVS) and zero current switching (ZCS) is achieved for the primary side of the converter by using secondary switches. Primary side switches are controlled by closed loop control topology. The secondary side is made with voltage doubler to obtain high voltage. Open loop and closed loop control of dual inductor current fed push pull converter simulation is finished by MATLAB/SIMULINK and their outcomes are analyzed.
This paper presents a study on a new full bridge series resonant converter (SRC) with wide zero voltage switching (ZVS) range, and higher output voltage. The high frequency transformer is connected in series with the LC series resonant tank. The tank inductance is therefore increased; all switches having the ability to turn on at ZVS, with lower switching frequency than the LC tank resonant frequency. Moreover, the step-up high frequency (HF) transformer design steps are introduced in order to increase the output voltage to overcome the gain limitation of the conventional SRC. Compared to the conventional SRC, the proposed converter has higher energy conversion, able to increase the ZVS range by 36%, and provide much higher output power. Finally, the a laboratory prototypes of the both converters with the same resonant tank parameters and input voltage are examined based on 1 and 2.2 kW power respectively, for veryfing the reliability of the performance and the operation principles of both converters.
This paper presents a phase shifted series resonant converter with step up high frequency transformer to achieve the functions of high output voltage, high power density and wide range of Zero Voltage Switching (ZVS). In this approach, the output voltage is controlled by varying the switching frequency. The controller has been designed to achieve a good stability under different load conditions. The converter will react to the load variation by varying its switching frequency to satisfy the output voltage requirements. Therefore in order to maintain constant output voltage, for light load (50% of the load), the switching frequency will be decreased to meet the desired output, while for the full load (100%) conditions, the switching frequency will be increased. Since the controlled switching frequency is limited by the range between the higher and lower resonant frequencies , the switches can be turned on under ZVS. In this study, a laboratory experiment has been conducted to verify the effectiveness of the system performance.
Mitigation of Power Quality Issues by Nine Switches UPQC Using PI & ANN with ...IJERA Editor
A nine-switch power converter having two sets of output terminals was recently proposed in place of the traditional back-to-back power converter that uses 12 switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to its many perceived performance tradeoffs like requiring an oversized dc-link capacitor, limited amplitude sharing, and constrained phase shift between its two sets of output terminals. Instead of accepting these tradeoffs as limitations, a nine-switch power conditioner is proposed here that virtually ―converts‖ most of these topological short comings into interesting performance advantages. Aiming further to reduce its switching losses, Harmonics, Voltage Sag & Swell an appropriate discontinuous modulation scheme is proposed and studied here in detail to doubly ensure that maximal reduction of commutations is achieved. With an appropriately designed control scheme with PI and ANN with Hysteresis controller then incorporated, the nine-switch converter is shown to favorably raise the overall power quality in Simulation, hence justifying its role as a power conditioner at a reduced cost.
Solid-State Transformer (S2T) also known as Power Electronic Transformer (PET) is applied in various industrial fields compared to the conventional transformer due to it flexible voltage transfer ratio, high power density, and low harmonic distortion. This paper presents the S2T of Single Phase Matrix Converter (SPMC) that acts as cyclo-converter. A 1kHz frequency was synthesized on the primary side of the transformer using Pulse Width Modulation (PWM) technique, whilst, the output converted by the SPMC that produces the 50Hz frequency. A part of AC to AC operation, the switching algorithm for safe-commutation technique is also presented to solve the commutation problem caused by the usage of inductive load. Minimization of size, losses and optimal efficiency are the advantages of this approach. The proposed model was simulated by using MATLAB/Simulink (MLS).
Сытник В. С. Основы расчета и анализа точности геодезических измерений в стро...Иван Иванов
В книге изложены вопросы теории и практики расчета, бценки
и анализа точности геодезических измерений, выполняемых при
возведении промышленных, жилых и общественных зданий й\цн-
женериых сооружений. На основе существующих в теории вероят^~—-
ностей
математической статистики и ошибок измерений рассмат
риваются методы расчета необходимой и достаточной точности гео
дезических измерений
применительно к определенным стадиям
строительно-монтажных работ и конструктивным решениям зданий
и сооружений. Значительное внимание уделено анализу точности
результатов геодезических измерений
Заковряшин А. И. Конструирование РЭА с учетом особенностей эксплуатацииИван Иванов
Показана роль конструкторского проектирования в обеспечении эффективности технического обслуживания РЭА по фактическому состоянию. В книге
взаимосвязанно решаются вопросы обеспечения ремонто- и контролепригодности
при конструировании РЭА. Ремонтопригодность рассматривается лак решающи”
фактор обеспечения эффективности применения аппаратуры. Область значений
конструктивных показателей РЭА определяется как результат решения задачи
оптимизации заданного качества функционирования.
1. * GB780016 (A)
Description: GB780016 (A) ? 1957-07-31
A mechanical current converter (contact rectifier) with commutating reactors
Description of GB780016 (A)
PATENT SPECIFICATION
Date of Application and filing Complete Specification: Oct. 27, 1954.
' y Application made in Germany on Nov. 3, 1953.
Complete Specification Published: July 31, 1957.
Index at acceptatice:-Class 38(2), Fl(AW:P:1).
International Classification:-H02n.
COMPLETE SPECIFICATION
A Mechanical Current Converter (Contact Rectifier) with Commutating
Reactors We, LICENTIA PATENT-VERWALTUNGSGMBH, a German Body Corporate,
of 31-32 Hohe Bleichen, Hamburg, Germany, do hereby declare the
invention for which we 5pray that a patent may be granted to us, and
the method by which it is to be performed to be particularly described
in and by the following statement: -
With mechanical current converters (contact converters) commutating
reactors are used in order to ensure a satisfactory operation of the
contacts. These reactors produce during the change of magnetisation a
low current step during which the contacts operate. If the alternating
voltage supplying such mechanical converters decreases below the
normal value, then it may happen that the low-current steps of the
commutating reactors become too long; moreover, the reactors' losses
and their inductance make themselves increasingly felt. It is possible
to reduce the length of the step by providing the reactors with a
winding which is provided with taps or with two or more windings which
can be switched-in in different ways. This possibility has the
disadvantage that, as a result of the change of the connection, the
magnitude of the step current (magnetising current) of the reactors
varies and that, therefore, also other auxiliary circuits of the
rectifier, such as contact by-pass circuits have to be changed. If the
number of turns is reduced it may happen that the magnetising current
2. increases to such an extent that the current converter does no longer
operate satisfactorily. Moreover, the change of the winding
connections of commutating reactors is difficult to perform.
Therefore, a multi-phase mechanical contact converter which is
connected to a multiphase transformer and has a reactor in series with
and at the alternating current side of each contact so as to produce a
low-current step each time the current wave passes through zero in
order to facilitate the current lPrice 3/6] commutation, is
characterised according to the invention in that each reactor is
divided into two or more partial commutating reactors which are
arranged in such a manner that the effective reactance can be varied
by 50 an alternative series or parallel connection of the individual
reactors, or by short-circuiting some or all but one of the reactors.
In order to secure that the step current of all the reactors in a
phase remains constant 55 or substantially constant, the individual
reactors may be so designed that they produce substantially the same
step current. A particularly simple arrangement can be obtained by
providing for each phase in series two 60 equal reactors.
The invention can be applied with particular advantage to an
arrangement with sixphase double-way connection of the rectifying
contacts in conjunction with an open 6 three-phase transformer
connection. Such an arrangement actually requires only three
commutating reactors in double-way connection. In view of the small
number of reactors which such an arrangement requires, a subdivision
of the reactors in each phase can be effected without increasing
unduly the first costs for the commutating reactors.
The above described rectifier connection is represented in the
accompanying drawing 75 as an example for an arrangement according to
the invention. As shown, the primary windings of the converter
transformer is delta-connected, and the secondary windings 1, 2, 3,
instead of being connected at their 80 centre points to form the
conventional sixphase diametric transformer connection, are completely
separated and form, what is called for the purpose of this
specification, an "open three-phase transformer connection". 85 Each
phase 1, 2, 3 is provided with two serially connected commutating
reactors 11, 12 and 21, 22 and 31, 32 respectively, one of each pair
of commutating reactors being adapted to be shunted by a disconnecting
90 7809016 No. 31001154.
780,016 switch 13, 23, 33 respectively. If the disconnecting switch is
in its position a (open position), then the shunt connection is
removed, whilst it is effective in the position b (closed position).
If one reactor is shortcircuited, the losses and the inductance of the
commutating reactance are reduced by one half, so that the efficiency
and the power factor of the converter are increased. Moreover, the
3. disadvantages of too long commutating reactor steps in connection with
commutating reactors used alternately for the positive and for the
negative current direction (double-way connection) as shown in the
drawing are overcome. With too long commutating reactor steps there is
a danger with arrangements of this kind that the reactors, after
termination of the contact period for current in one direction, have
not changed their saturation quickly enough at the start of the
current flow in the opposite direction.
As a result of the application of the invention it is possible to
dimension the serially connected commutating reactors in respect of
full supply voltage in such a manner that the length of the step is
comparatively large whereby the rectifier is safeguarded against
voltage or current disturbances. On the other hand, if the three-phase
supply voltage is reduced to a half of the original value, then one of
the reactors can be short-circuited so that again the same favourable
length of the step is obtained as without short-circuiting at full
supply voltage.
Apart from the commutating reactors, also the secondary winding of the
transformer may be switched over in order to avoid transformer losses
and leakage inductances during operation with partial voltage. For
this purpose the secondary winding of the transformer is provided, for
instance at its centre, with a tap b' to which at partial voltage the
one conductor feeding the contacts is switched over from contact a.
And if one of the reactors, e.g., 12, 22, 32, is arranged in the said
conductor adjacent to the transformer winding, it is then possible to
short-circuit this reactor and part of the transformer winding by a
single switching manipulation from ad to b'.
But it also possible to subdivide the secondary windings of the
transformer and to connect them alternatively in series or in parallel
as required.
The invention is of particular interest in its application to plants,
e.g., electrolytic plants, which work over long periods with a voltage
considerably lower than their nominal voltage and which require, for
economic reasons that the efficiency and the power 60 factor should be
as high as possible.
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* 5.8.23.4; 93p