A Novel Controller for Switched Reluctance Motor

Abstract

Electrical drives are playing an important role in modern industries. In the last two decades an electrical drive named the Switched Reluctance Motor (SRM) drive is receiving considerable attention from industry in adjustable speed drives since it is characterized by robust construction, high operation reliability and efficiency. The successful application of SRM in automobiles depends on the proper motor design and overall cost of the drive which includes converter and controller costs. However, there have been inadequate design experience for SRM’s as compared with more mature BLDC motors and induction motors, and applications are limited so far due to complex design procedure. Therefore, it is necessary to develop a set of design procedures for SRMs. Although the design principles of SRMs are available in different literatures; there is no clear idea in the basic design procedure. These procedures require extensive prior knowledge and experience in designing. The procedure outlined in this thesis requires only basic dimension data for SRM’s. The empirical formulas are used for basic design and since it is difficult to accurately incorporate the saturation effect and the detailed geometrical information in the empirical formulas, the FEM was used for fine-tuning and validating the design. For dynamic behaviour of a SRM and for controller and converter design, the knowledge of the magnetization curves is very essential. Therefore this thesis discusses how the magnetic characteristics of SRMs are obtained by experimental, analytic and FEM. Thereafter a new method of finding the motor winding inductance at different rotor position using 3D FEM is carried out to validate the results as obtained by experimental method. The SRM drive consists of a power converter section that sequentially connects the motor phases independently and a control section that processes rotor position information form a position sensor and generates the phase excitation pulses. A new method to estimate the initial rotor position of the SRM at stand still and during running condition is proposed without the need of magnetisation curves. A pair of position sensors is used to detect the rotor positions and the output signals of the sensors are used as the basic triggering pulses for main switches. The proposed method was implemented by the simple microcontroller based systems. A known sensorless method of finding the rotor position is used to validate the correctness of the proposed method. The proposed method is implemented with the 8/6,1 kW,12000 RPM 8/6 SRM. The experimental results shows that the proposed rotor estimation technique provides good accuracy at different operating conditions