Commutatorless Motor Research Articles

Development of the C-dump topology-based four-level converter for switched reluctance motor drives

Demand for brushless and commutator-less motor drives is increasing day by day for industrial applications. So improvement in switched reluctance motor (SRM) drives remains an important research area due to cheap and maintenance free motor construction. In literature, various converter topologies and their control strategies are described, however the C-dump-based converter topologies have gained interest owing to its ability to retrieve the stored magnetic energy. This can be further utilised to achieve desirable performance characteristics. The paper addresses the development of a drive system for a four phase, 8/6 switched reluctance motor. The drive system consists of a power circuit and its control scheme. The power components are designed for a 4-phase, 3 hp, 8/6 SRM which is used to obtain the experimental results. A simple PI-based speed control scheme is implemented which is suitable for low power applications such as cooling fan, blower, etc. A C-dump-based converter is proposed which allows reduction of switching losses, especially in the low speed range and it eliminates energy intake from the source during energy discharge process.

Harmonics Mitigation in LCI-Fed Synchronous Motor Drives

A load-commutated inverter (LCI) fed synchronous motor (SM) is operated as an adjustable speed drive (ASD) in high-power applications. These drives are known as commutatorless motor (CLM) drives and posses many promising features like high efficiency, economic operation, and flexibility of control in high-power ratings. The CLM drives are used in compressors, blowers, fans, pumps, and mill drives for a range of industries as mining, water treatment plants, chemical, paper, textile, cement, rolling mills, and petrochemical plants. However, the power quality (PQ) problems at ac mains have been the concerns in these drives as the LCI has front-end thyristor converter injecting harmonics in the supply. This paper investigates various topologies for the mitigation of PQ problems in LCI-fed SM drives using multipulse ac-dc converters. A set of hybrid topologies is proposed, which use a combination of a passive filter with a multipulse converter to feed CLM. A basis for selection of a suitable ac-dc converter is presented for PQ improvement at the input mains of the LCI-fed SM drives.

Power quality improvement in load commutated inverter-fed synchronous motor drives

The load commutated inverter (LCI)-fed synchronous motor (SM) drive, also known as commutatorless motor (CLM) drive, is popular in high power applications. Most promising features of these drives include high efficiency, economic operation, flexibility of operation and variable speed in high power range, which led to their applications in blowers, fans, pumps, mill drives for a range of industries as mining, water treatment plants, chemical, paper, textile, cement, rolling mills and petrochemical plants. However, the power quality (PQ) concerns have resulted in a set-back for such applications of these drives. This study investigates various topologies for the mitigation of PQ problems in LCI-fed SM drives using multi-pulse AC-DC converters. A set of hybrid topologies is proposed to feed CLM, which use a multi-winding transformer and diode rectifiers with a chopper cascaded named as -rectifier-chopper-. These topologies improve PQ at AC mains, that is, reduce total harmonic distortion in the input current and correct the power factor. It also presents a basis for selection of a suitable AC-DC converter for PQ improvement at the input AC mains of the LCI-fed SM drives.

A Simplified Analytical Averaged Model of a Thyristorized Commutatorless Series Motor

This paper proposes a simplified analytical averaged model of a thyristorized commutatorless series motor. The motor operation is generally complicated due to the complexities present in the three-phase synchronous machine used and the nonlinearities introduced by the switching operation of the power electronic converter that is feeding the electrical machine. The simple analytical model is formulated in light of a conventional dc series motor and is found to be approaching the simplicity of a conventional dc series motor both in dynamic condition and steady state. The developed simplified model is found to yield results closely tallying with those obtained from a "detailed numerical model" developed earlier, which is totally numerical in nature. The results are also validated experimentally on a small laboratory-built prototype. The developed model lays the foundation of controlling the motor for different industrial loading applications. One such application, viz., constant torque loading, is considered to show that the control strategy adopted on the basis of the discussed model works satisfactorily to develop a constant torque according to a given torque reference irrespective of load disturbances

Analysis, simulation and test results for a cycloconverter-fed AC commutator-less motor drive with a modified machine model

Digital simulation and practical implementation aspects of a self-controlled cycloconverter-fed synchronous motor drive for high-power and low-speed applications are discussed. The digital simulation is achieved in the Park reference frame with a modified machine model to account for discontinuous current operation in the armature and the field. The practical drive is realised using a hybrid controller developed around an inexpensive PC-based system to achieve high reliability and a lower sampling time. The test results are compared with the simulation results and they show close agreement.

Simplified steady-state model of an SCR-inverter-based load-commutated commutatorless series motor

This paper presents a simplified analytical model of a silicon-controlled-rectifier based, load-commutated inverter driven, commutatorless series motor to predict its speed-current, torque-current and torque-speed characteristics. The model has been formulated, keeping in view the steady state equivalent circuit of a conventional DC series motor. The proposed analytical expressions relating torque and current with speed are found to follow an inverse law and that relating torque and current is found to be parabolic, as is expected in a "series" machine. The drive has been implemented, loaded with a DC generator and experimentally similar characteristics have been obtained, as predicted by the analytical model. The characteristics obtained experimentally are seen to follow the ones, predicted by the analytical model closely.

High output power characteristics of revolving‐armature type commutatorless motor

The authors and others developed a 15 kW revolving-armature type commutatorless motor deriving high magnetic loading. The commutatorless motor was first manufactured with interpole and compensating windings having a construction allowing easy installation and removal of interpoles. It was found from this experiment that this motor was improved in overload torque and the effect of interpoles did not affect compensating windings of the spare angle improvement. Therefore, the compound commutatorless motor (with compensating windings) was manufactured as an experiment. A high output of 190% power was derived by this motor and compensating windings were not needed. By characteristics analysis and simulation, the main factor by which this high output was obtained was that the leakage reactance Xl of this motor was half that of old commutatorless motors. This paper reports this effect, including the experimental data. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 82–95, 1997

An inverter-fed self-controlled commutatorless series motor with the field winding in the DC link

This paper examines the basic operation of a self-controlled synchronous motor driven by a three-phase MOSFET inverter with the field winding located in the DC link, yielding inherent series characteristics like a DC series motor. A new approach to the analytical and experimental study of the drive with the switches conducting for both 120/spl deg/ and 180/spl deg/ is presented, and typical results, both simulation and experimental, are shown and the performance characteristics compared. The effect of shifting the rotor position sensor is studied for both cases, as well as for four-quadrant operation. It is observed that the resulting drive system is simple, able to operate with reduced torque ripples and voltage spikes, and the characteristics of the drive are well suited for traction/transit propulsion applications and battery/flywheel energy storage systems.

Fundamental design and electrical characteristics of superconducting commutatorless motor

AbstractSince there are no iron cores in the rotor and stator windings of superconducting synchronous motors, some reactances are intrinsically smaller than those of conventional motors. Thus the low synchronous reactance would be expected to improve the torque‐ampere ratio stability and the overload capacity in case of the variable‐speed drive system of a load‐commutated inverter due to the small armature reaction. Moreover, the low subtransient reactance may contribute to lessen the voltage stress during the shortened commutating period, especially in current source‐type inverter (CSI) systems.In this paper, after presenting analytical formulas needed for a machine design, one design algorithm is described, citing one example of an experimental CSI‐fed superconducting motor of 30 kVA which will be fabricated. Further, the distinguished features in its operation, as expected in the foregoing, are verified by the computer simulation study in comparison with a conventional machine in terms of a high specific power density, an extension of stable power limit, and so on.

Fundamental Design and Electrical Characteristics of Superconducting Commutatorless Motor.

Since there are no iron cores in the rotor and stator windings of superconducting synchronous motors, some reactances are intrinsically smaller than the ones of conventional motors. So the low synchronous reactance would be expected to improve the torque-ampere ratio stability and the overload capacity in case of the variable speed drive system of a load commutated inverter due to the small armature reaction. Moreover, the low sub-transient reactance may contribute to lessen the voltage stress during the shortened commutating period, especially in current source type inverter (CSI) systems.In this paper, after presenting analytical formulas needed for a machine design, one design algorithm is described, citing one example of an experimental CSI fed superconducting motor of 30 kVA which will be fabricated. Further, the distinguished features in its operation, as expected just above, are verified by the computer simulation study in comparison with a conventional machine in terms of a high specific power density, an extension of stable power limit and so on.

Efficiency optimized speed regulator system for commutatorless motor.

A new variable speed control method for the Commutatorless Motor is proposed on the basis of Modern Control Theory, to provide not only a quick response for speed reference but a high efficiency operation. The summarized contents of the proposed method are the following.(1) The optimum ratio of armature current to field current making the efficiency maximum is derived.(2) Ordinarily, as a commutatorles motor has an unstable tendency when it is driven in the manner of a constant commutation margin angle, the air gap flux is necessary to keep constant by sensing the air gap flux. However, the proposed method does not need the flux sensing because of estimating all the state variables with accessible state variables.(3) For reducing the production cost, the technique that constructs the feedback control system using the accessible state variables is employed.(4) As a result from considering thyristor commutating mechanism, a new current controller which protects the motor system from the commutation failure is introduced.Finally, the proposed control method is applied for the numerical commutatorless motor model, and its usefulness is confirmed through the simulation.

Fundamental characteristics of an exciterless and brushless‐type commutatorless motor driven by a voltage source inverter

Fundamental characteristics of an exciterless and brushless‐type commutatorless motor driven by a voltage source inverter

An exciterless- and brushless-type commutatorless motor fed from a transformer in parallel with a voltage source inverter

A novel exciterless- and brushless-type commutatorless motor driven by a voltage source inverter is presented, and the analysis of the characteristics and the test results are reported. In the commutatorless motor, the stator armature winding is connected electrically with the secondary winding of a transformer. An AC exciting current flows in the armature winding simultaneously with the load current. The ratio between the number of poles made by the load current and the number of poles by the AC exciting current is 2 or 1/2. Thus, the motor can be made exciterless and brushless. Since the rotating direction of the rotating field made by the AC exciting current is opposite to that of the rotor in this commutatorless motor, speed control in a low-speed range is possible, because a large current can flow in the field winding even if the rotor rotates in a low-speed range. As a result, the motor can be controlled in a wide range, from high speed to low speed. It has been found from the analysis and the test results that a shunt wound characteristic between the speed and the torque and other characteristics can be obtained. >

複巻励磁サイリスタ直流機

The quick response characteristics and good controllability of a 7-phase compound type D.C. commutatorless motor (abbreviated as 7-phase compound TBM) are comparable, in principal, to those of ordinary D.C. compound motor. Its operation modes can be accompalished by phase control through the use of 3-phase and 7-phase thyristor rectifiers.This report summarizes both the design for the compound excitation circuit and the experimental results of the 7-phase compound TBM. When the motor with usual separate or shunt excitation is started or impressed by a large load, the circuit generally yields a large rush current. So that the motor needs the large capacity of a power source. Contrary to this, the 7-phase compound TBM generates a large starting torque and small rush current since the motor speed goes down for a suddenly impress load. Therfore the capacity of a power source of the 7-phase compound TBM can be small.This report shows that (i) the characteristics of the compound excitation can be changed by the turn ratio of a current transformer, (ii) the margin angle of commutation of the 7-phase compound TBM is larger than that of the shunt TBM, and (iii) the 7-phase compound TBM fits for the various machines with the wide speed varying load, such as winches and electric propulsion systems.

Fundamental characteristics of an exciterless and brushless type commutatorless motor drive with a voltage source inverter.

Fundamental characteristics of an exciterless and brushless type commutatorless motor drive with a voltage source inverter.

Brushless self-excited type commutatorless motor based on microcomputer control.

Brushless self-excited type commutatorless motor based on microcomputer control.

High‐power factor operation scheme for adjustable speed commutatorless motor drives

High‐power factor operation scheme for adjustable speed commutatorless motor drives

Steady analysis and adjustable speed drive of brushless self-excited type commutatorless motor with non-salient pole.

Steady analysis and adjustable speed drive of brushless self-excited type commutatorless motor with non-salient pole.

High power factor operation scheme for adjustable speed commutatorless motor drives.

High power factor operation scheme for adjustable speed commutatorless motor drives.

Analysis of characteristics of claw‐pole commutatorless motor using equivalent magnetic circuit

Analysis of characteristics of claw‐pole commutatorless motor using equivalent magnetic circuit