Alternator loss breakdown and use of alternative rectifier diodes for improvement of vehicle electrical power system efficiency

The losses in the electrical power generation system of a conventional internal combustion engine (ICE) vehicle is investigated. The system consists of a six-phase Lundell alternator and a six-phase passive rectifier. The losses of the alternator are measured using a test rig that simulates the ICE operation. It is shown that the Press-fit PN diodes currently in use in conventional alternator rectifiers are responsible for a typical 10-12 % conversion loss. Thus, a number of comparable alternatives to the Press-fit PN diodes are identified. Several passive rectifiers are built and tested in order to evaluate the efficiency improvement of the rectifying stage as well as of the combined alternator-rectifier system. Preliminary results indicate a positive trend for the rectifier conversion efficiency, suggesting a significant impact on the maximum power generation capability of the system.