Document Type : Review Article
Authors
1 Department of Electrical Engineering, Shahid Beheshti University G. C., Tehran, Iran
2 Department of Electrical Engineering, West Tehran Branch, Islamic Azad University, Tehran, Iran
Abstract
The switched reluctance motor is a singly excited, doubly salient machine which can be used in the generation mode by selecting the proper firing angles of the phases. Due to its robustness, it has the potential and the ability to become one of the generators to be used in the harsh environment. This paper briefly discusses the energy conversion by a switched reluctance generator (SRG) when two switches per phase converter circuit and discrete position sensors are employed. It is well known fact that, as the generator’s speed increases by a prime mover and the shape of the current waveform changes in such a way that limits the production of generating voltage. At high speeds, it is possible for the phase current never reaches the desired value to produce enough back-EMF for sufficient voltage generation, therefore, the output power falls off. In order to remedy this problem, the phase turn on angle is advanced in a way that the phase commutation begins sooner. Since one of the advantages of this type of generator is its variable speed then, the amount of advancing for the turn on angle should be accomplished automatically to obtain the desired output voltage according to the speed of the generator, meaning, as the generator speed increases so should the turn on angle and vice versa. In this respect, this paper introduces an electronic circuit in conjunction with time reshaping of the command pulses obtained from position sensors and the drive converter to achieve this task for a desired output voltage when a SRG feeding a resistive load. To evaluate the generator performance, two types of analysis, namely numerical technique and experimental studies have been utilized on a 6 by 4, 30 V, SRG. In the numerical analysis, due to the highly non-linear nature of the motor, a three dimensional finite element analysis is employed to calculate some of motor parameters and then using these parameter, current shape and magnitude are computed, whereas in the experimental study, a proto-type generator and its circuitries have been built and tested using two-switch per phase converter. A linear analysis of the current waveform for the generator under different advancements of the turn on angle has been performed numerically and experimentally and the results are presented.
Keywords
)