A vehicle electric power generation system with improved output power and efficiency

This paper presents a vehicle electric power generation system with improved output and efficiency. At low speed, the output power of the system is maximized by using a controllable rectifier to optimize the operating conditions of the alternator. The controllable rectifier is synchronized with the alternator based on the zero-crossing information of the third harmonic voltage. The output power is controlled by shifting the phase voltage with respect to the third harmonic voltage. At high speed, the system output power and efficiency are increased by changing the number of turns of the alternator stator windings. Winding reconfiguration is realized by winding taps and use of two rectifiers and two switches. A proof-of-concept system has been built and tested in the laboratory. The test data show that the new system can increase the output power significantly at both low and high speed. In the present range in which the alternator is operated most of the time, the winding reconfiguration increases both the output power and efficiency. For the same output power as a production alternator, the winding reconfiguration unit improves the efficiency by 21% (from 47% up to 57%).