1993 Volume 113 Issue 3 Pages 349-356
Permanent-magnet brushless direct-current motors are easy of maintenance and control, compaired with direct-current motors. Therefore, they are attracting attention today. In this paper, the authors discuss non-salient pole brushless direct-current motors. Usually, the quadrature armature current which contributes to torque generation is supplied in this motor. But, in the case that the source voltage cannot be increased, by supplying the direct armature current, that is, equivallently weakening field, a quadrature armature current can be increased. Consequently, the motor torque increases.
In the case that the load characteristics are settled, the motor torque can have a maximum Tm by adjusting a direct armature current. At this time the rotational speed and output are maximum also. Tm changes with the change of the motor parameters. Consequently, the motor parameters which maximize Tm are optimal. In this paper, the auhors have clarified an optimal parameter determination method considering of the load torque-speed characteristics and armature resistance, and the power factor and efficiency where the motor has optimal parameters and generates the maximum output. Further, the authors have verified the obtained theory through experiment.