Attempt to Evaluate the Building Factor of a Stator Core in Inverter-Fed Permanent Magnet Synchronous Motor

This paper presents an attempt to evaluate the building factor of a stator core made of nonoriented silicon steel laminations. The stator core is used in a synchronous motor with buried permanent magnets driven by a voltage source three-phase inverter with classical pulse-width modulation (PWM) control. The building factor is the ratio between the iron loss density in the stator core and the specific iron loss density of the material. It then gives an evaluation of the impact of the core manufacture and the motor geometrical configuration on the stator iron losses. A first experiment is conducted to measure the iron losses of the inverter-fed motor in no-load condition. The material-specific iron losses are then evaluated by trying to apply similar magnetic flux density conditions in a wound laminated ring. The results show a decrease of the building factor with the PWM carrier frequency.