R. Krishnan

Design and Development of Low-Cost and High-Efficiency Variable-Speed Drive System With Switched Reluctance Motor

Low-cost switched-reluctance-motor (SRM) drive systems are actively sought for high-efficiency home appliances and power tools. Minimizing the number of switching devices has been in power converters that is the main method to reduce drive costs. Single-switch-per-phase converters have been cost effective due to the compactness of the converter package resulting in a possible reduction in their cost. However, some of the single-switch-per-phase converters have the drawbacks that include higher losses and low-system efficiency. In order to overcome these shortcomings, the choice narrows down to the split ac converter through the quantitative analysis in terms of device ratings, cost, switching losses, conduction losses, and converter efficiency. Simulations to verify the characteristics of the converter circuit and control feasibility are presented. The motor drive is realized with a novel two-phase flux-reversal-free-stator SRM and a split ac converter. The efficiency with various loads is numerically estimated and experimentally compared from the viewpoint of subsystem and system in details. The acoustic noise with no load and full load is also compared. The focus of this paper is to compare the considered split ac converter to the asymmetric converter through experiments and demonstrate that the split ac converter is the most advantageous with respect to cost, efficiency, and acoustic noise

Single-Controllable-Switch-Based Switched Reluctance Motor Drive for Low Cost, Variable-Speed Applications

A new low-cost, brushless variable-speed drive requiring only a single controllable switch is presented. The proposed converter (referred to as new single-switch converter) overcomes the drawback of the original single-switch-based four-quadrant motor drive in terms of recovery energy circulation. The drive system is realized using an asymmetric two-phase switched reluctance motor (SRM), the proposed converter, and DSP controller. The new drive system retains the unique features of self-starting for all rotor position and four quadrant operation of the original single-switch-based SRM drive system. This paper presents operation principle, modeling, simulation, and design considerations of the converter in conjunction with the motor. Simulation results are based on a nonlinear model of the motor drive system. A prototype drive has been built and tested to verify its practical viability. The experimental results correlate well with the simulation, and demonstrate a performance comparable to conventional asymmetric bridge converter-based drive with two switches per phase. The market relevance of this new drive system is primarily due to its lowest cost structure, packaging compactness, self-starting feature, variable-speed operation and four-quadrant capability. Because of these features, the new drive system offers a viable alternative to conventional fixed-speed brush-commutator motors and variable-speed permanent magnet brushless dc motor drives in many high volume applications in the low-cost, energy efficient, high-volume categories such as fans, blowers, hand tools, and small appliances.

Novel Two-Switch-Based Switched Reluctance Motor Drive for Low-Cost High-Volume Applications

This paper presents a low-cost energy-efficient variable-speed drive for high-volume applications, such as home appliances, fans, and hand tools. A new low-cost power converter is proposed, and the drive system is realized using a two-phase switched reluctance motor and the proposed converter. The motor is capable of self-starting at any rotor position and four-quadrant operation. The converter is unique in that it has two capacitors for the energization of each phase and uses the main phase winding as energy storage for the secondary capacitor C2. The converter employs a single-switch-per-phase configuration, hence requiring only two controllable switching devices in total. The converter is inherently suited for two-phase motors having asymmetric stator phases to realize self-starting and speed reversal. Simple starting and C2 voltage control schemes are presented. This paper describes the analysis, modeling, control algorithm, and design considerations for a prototype drive system. Experimental verification and correlation with simulation results are presented. The proposed drive system offers a low-cost brushless variable-speed drive that is a potential alternative for conventional brush-commutator motors in high-volume applications.

Single-controllable-switch-based switched reluctance motor drive for low-cost variable- speed applications

A new low-cost, brushless variable-speed drive requiring only a single controllable switch is presented. The proposed converter (referred to as new single-switch converter) overcomes the drawback of the original single-switch-based four-quadrant motor drive [8] in terms of recovery energy circulation. The drive system is realized using an asymmetric two-phase switched reluctance motor (SRM) and the proposed converter. The new drive system retains the unique features of self-starting for all rotor position and four quadrant operation of the original single-switch-based switched reluctance motor drive system. The paper presents operation principle, modeling, simulation, and design considerations of the converter in conjunction with the motor. Simulation results are based on a nonlinear model of the motor drive system. A prototype drive has been built and tested to verify its practical viability. The experimental results correlate well with the simulation, and demonstrate a performance comparable to conventional asymmetric bridge converter based drive with two switches per phase. The market relevance of this new drive system is primarily due to its lowest cost structure, packaging compactness, self-starting feature, variable-speed operation and four-quadrant capability. Because of these features, the new drive system offers a viable alternative for conventional fixed speed brush-commutator motors and variable-speed permanent magnet brushless dc motor drives in many high volume applications in the low-cost, energy efficient, high-volume categories such as fans, blowers, hand tools and home appliances.

Design and Development of Brushless Variable Speed Motor Drive for Low Cost and High Efficiency

Low cost brushless motor drive systems are actively sought for high efficiency home appliances and power tools. Minimizing the number of switching devices has been in power converters is the main method to reduce drive costs. Single-switch-per-phase converters have been cost-effective due to compactness of the converter package resulting in a possible reduction in their cost. However, some of single-switch-per-phase converters have the drawbacks that include higher losses and low system efficiency. In order to overcome these shortcomings, the choice narrows down to the split AC converter through the quantitative analysis in terms of device ratings, cost, switching losses, conduction losses, and converter efficiency. Simulations to verify the characteristics of the converter circuit and control feasibility are presented. The motor drive is realized with a novel two-phase flux-reversal-free-stator switched reluctance motor and a split AC converter. The efficiency with various loads is numerically estimated and experimentally compared in this paper. The acoustic noise with no load and full load is also compared. The focus of this paper is to compare the considered split AC converter to the asymmetric converter through experiments and demonstrate that the split AC converter is the most advantageous with respect to cost, efficiency, and acoustic noise

An automated reconfigurable FPGA-based magnetic characterization of switched reluctance machines

The flux-linkage profile of a switched reluctance machine (SRM) is an important parameter in the verification of the design and performance of the drive. Due to the double salient structure of the SRM, the profile is a function of both rotor position and excitation current. In addition, the effects of eddy current losses and resistance changes make the measurement of SRM magnetic characteristics challenging. This paper describes an automated method to measure the magnetic characteristics of SRM drives using reconfigurable FPGA hardware programmed graphically with National Instruments LabVIEW. The FPGA-based measurement system provides advantages for the measurement and control of electric machines due to the timing, triggering, and custom logic capabilities of the reconfigurable chipset. A measurement methodology based on 60 Hz sinusoidal excitation using a variable AC power supply is developed which provides an alternative to time domain integration approaches for magnetic characterization. An automated software environment provides the ability to accurately measure voltage and current waveforms, perform sensor calibration, acquire rotor angular position, and eliminate error from thermal and eddy currents effects. The measured flux-linkage profile is correlated with finite element analysis results for validation of the proposed method.

Low-Cost Position Sensorless Switched Relutance Motor Drive Using a Single-Controllable Switch Converter

Elimination of rotor position sensors mechanically coupled with the rotor shaft is attractive to variable speed drives primarily due to increased system reliability and cost reduction. In this regard, search for a simple and robust position sensorless control has been intensified in past few years specifically for low-cost, high-volume applications such as home appliances. This paper describes a new parameter insensitive position sensorless control for switched reluctance motor (SRM) drives satisfying such a need in this market segment. Two consecutive switch-on times of the controllable switch in hysteresis current control are compared to estimate the rotor position and speed. The proposed sensorless control algorithm is very simple to implement since it does not depend on extensive computation or any additional hardware. In addition, the proposed method is robust in that its dynamic performance is least affected by system parameter variations. The proposed approach is demonstrated on a single-controllable-switch-converterdriven SRM with two-phases that lends itself to a system with low cost and compact packaging which comes close to the intended applications. Analysis and simulation results followed by experimental verification are presented to demonstrate the feasibility of the proposed sensorless control method.

M-Phase N-Segment Flux-Reversal-Free Stator Switched Reluctance Machines

This paper describes a class of switched reluctance machines (SRM) whose stators have no flux reversals. Previously published work describes a two-phase flux-reversal-free-stator SRM and this paper extends the concept to an SRM with any number of phases. For the first time in literature, SRMs with flux reversal free stators and flux reversal free rotor back irons are developed in concept and presented in their realizable forms. Reversal of magnetic flux in the iron core results in increased core-loss when compared to iron cores which do not experience flux-reversals. The novel SRMs in this paper have balanced radial forces. In addition, the stators can be constructed in a segmental fashion. The stators of the segmental SRM are magnetically isolated from one another. Segmental stators are advantageous in high power applications and applications where the stator diameter is limited by the maximum size of the stamping die. This paper also contains a generalized design method which describes how to accomplish an n-segment stator from an m-phase SRM. Furthermore, a sub-class of SRMs is also presented which, in addition to be above stated advantages has no flux-reversals in the rotor back-iron. Three novel three- phase SRMs are compared to a conventional SRM through finite element (FE) simulations. Static and dynamic finite element simulations presented show core-loss, efficiency, output power, torque ripple and radial forces for all four machines. The flux- reversal-free-stator concept is verified by FE simulations.

Parameter insensitive sensorless control of single-controllable-switch-based switched reluctance motor drive

Elimination of rotor position sensors mechanically coupled with the rotor shaft is attractive to variable speed drives primarily due to increased system reliability and cost reduction. In this regard, search for a simple and robust position sensorless control has been intensified in past few years specifically for low-cost, high-volume applications such as home appliances. This paper describes a new parameter insensitive position sensorless control for switched reluctance motor (SRM) drives satisfying such a need in this market segment. Two consecutive switch-on times of the controllable switch in hysteresis current control are compared to estimate the rotor position and speed. The proposed sensorless control algorithm is very simple to implement since it does not depend on extensive computation or any additional hardware. In addition, the proposed method is robust in that its dynamic performance is least affected by system parameter variations. The proposed approach is demonstrated on a single-controllable-switch-converter-driven SRM with two-phases that lends itself to a system with low cost and compact packaging which comes close to the intended applications. Analysis and simulation results followed by experimental verification are presented to demonstrate the feasibility of the proposed sensorless control method.

Comparison of Two Switched Reluctance Motors with No Flux-Reversal in the Stator

A comparison of two configurations of a novel two-phase switched reluctance machine (SRM) with no flux reversal in the stator iron is presented in this paper. Conventional SRMs have flux reversals that occur in sections of the yoke during commutation. The two novel SRMs compared in this paper have six stator poles. Each phase comprises of three poles separated by 120deg. The two rotor configurations contain three poles and nine poles, respectively. The comparison includes inductance and torque profiles, self-starting capability and torque ripple, weight, radial forces, core losses and in addition the unique features of the flux-reversal-free-stator SRMs. The results provide an indication of which machine is best suited for a particular application. Data for the comparison is obtained from dynamic finite element simulations