M.Sc. (Electrical & Electronic Engineering) / The behaviour of alternating current machines being fed from an electronic commutator is investigated. The performance of compound power switches for use in electric vehicle drives are examined. A detailed study on switching losses and base current characteristics based upon experimental measurements was carried out. With further reference to power switches the merit, development and functioning of an electronic commutator is discussed. Because of the close association between this study and electric vehicle drives, a comparative study of the performance of different rotor types within the same machine was executed. Attention is paid to torque and efficiency characteristics in particular. The influence of voltage and current harmonics was established by comparative testing of the machine with sinusoidal and electronic commutator excitation. The study shows that the highest specific power was attained with the alternating current machine with a wound rotor (synchronous machine) while there seems to be merit in the use of permanent magnet rotors for electric drives as well. On the average the use of electronic commutator excitation resulted in an efficiency decrease of approximately 15% for the a.c. machine with different rotor types. Efficiency and torque for an induction machine with solid rotor were disappointing so that there seems to be little application for solid steel rotors. A simple model for the synchronous machine with wound rotor was developed to explain the dependence of torque and efficiency upon speed of rotation and commutation angle. To conclude, guidelines are given for future studies on electric vehicle drives and machine types as primary drive.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:12395 |
| Date | 25 September 2014 |
| Creators | Loots, Gerhard Waldemar |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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