A motor design with self-adjusting flux capability for wide-speed-range automotive applications

One of the most common issues in permanent magnet motors for automotive applications is to improve their capability of operating over very wide speed ranges. For this purposes, various motor design techniques have been proposed in the literature. After a brief review of these techniques, the paper presents an idea for improving the flux weakening capability of permanent-magnet reluctance-assisted motors. The idea is based on using an auxiliary field circuit embedded in flux barriers and used to partly demagnetize the motor above the base speed. The field circuit is fed by a brushless permanent-magnet exciter and a diode rectifier. While at low speed the field is not energized, it automatically activates above the base speed by means of a centrifugal switch. As discussed in the paper, the auxiliary field current increases linearly with the speed so as to progressively reduce motor flux with a consequent beneficial reduction in the current to be fed by the inverter for flux regulation.