Practical field-weakening performance of the five classes of brushless synchronous AC motor drive

The effect of stator resistance, magnetic saturation and iron losses on the field weakening performance of synchronous reluctance and surface permanent magnet motors is examined. It is shown that the constant power speed range is relatively unaffected by stator resistance and iron losses but is strongly influenced by saturation. Methods for estimating the reduction in constant power speed range are described. The results are validated by comparisons with experimental measurements for a surface permanent magnet motor and two axially-laminated synchronous reluctance motors