Cheewoo Lee

Novel Two-phase Switched Reluctance Machine using Common-Pole E-Core Structure: Concept, Analysis, and Experimental Verification

A novel two-phase switched reluctance machine (SRM) with a stator composed of E-core structure having minimum stator core iron is proposed. The E-core stator has three poles with two poles at the ends having windings and a center pole containing no copper windings. The center stator pole in the E-core is shared by both phases during operation. The air gap around the common stator pole has constant and minimum reluctance irrespective of rotor position by its unique design, and the two remaining stator poles at the ends experience variable reluctance with respect to rotor position. The stator is constructed with two independent and physically separate E-cores, and the rotor is composed of ten poles. Other pole combinations are possible. Phase excitation in the novel SRM gives short flux paths, hence reducing the magnetomotive force required to drive the machine, resulting in significant reduction of copper wire and core losses compared to existing two-phase SRMs with flux paths that traverse the entire stator back iron. The concept and principle of operation of this novel SRM and its comparison to existing two-phase SRMs are detailed in this paper. Comparison between finite-element simulations and magnetic equivalent circuit (MEC) analysis for inductance are made and compared to experimentally measured characteristics. Furthermore, comparisons between a conventional two-phase SRM and the novel SRM are made in terms of its weight and output torque. Manufacturability and cost savings of the unique SRM structure are presented. It is shown that the E-core SRM using common stator pole has 50% less iron in the magnetic path compared to a conventional two-phase SRM.

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

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

A Study on Comparison of Two phase SRMs

In small-power applications, variable-speed motors having high efficiency and controllability become more dominant than brushed DC motors. BLDC motors with permanent magnets in the rotor and SRMs directed by reluctance torque due to no permanent magnets have been strongly studied as a candidate. Compared to the BLDC motors, SRMs are more suitable for low-cost applications since the magnetic structure is simple, mechanically robust, and cheap due to no additional excitation in the rotor such as copper wire, aluminum, and permanent magnets. In addition, relatively small number of phases in single and two-phase SRMs allows more cost savings with regards to material in the motor and switching devices in the converter. In this paper, several 2 phase SRMs are compared to a 3 phase 6/4 SRM in terms of flux distribution in key parts of the motors.

The Study on Magnetic Characteristics of 2 Phase SRM with Self-Starting Capability

Cost reduction requires lowering number of power devices used in the converter driving SRM. This is quite feasible in SRM drive systems than in other drive systems. This paper deals with analysis and simulation of a novel two phase SRM. A novel two phase SRM has high performance, self-starling capability, high efficiency, and low manufacturing cost. Additionally, the stator back iron does not experience any flux reversal as the flux is in the same direction whether phase A or B is excited leading to a greater reduction in core losses. The magnetic analysis and design considerations of the novel two phase SRM have been obtained by the finite element analysis (FEM).

PLL control scheme for high performance SRM drive

The switched reluctance motor (SRM) provides good adjustable speed characteristics. However, higher torque ripple is one of a few disadvantages of SRM drives. The SRM has torque ripple if it is not operated with an MMF current specified for switching angle and phase voltage. This paper describes the robust control scheme that permits the developed torque to be flat by using a PLL (phase locked loop) controller. In this control scheme, the locked phase signal of the PLL robustly controls the switching dwell angle and its loop filter signal controls the switching voltage adaptively. Experimental results show that stable dynamic performance is obtained for torque and speed together with low torque ripple on the operation of variable loads.