直流电动机中的箝位效应兼论无刷直流电动机之实质

Clamping Effect in DC Motor-Comment on Essential of Brushless DC Motor

无刷直流电动机的出现,使得直流电动机与同步电动机的区别变得模糊了。直流电动机和同步电动机的关键,在于电枢磁动势与直流励磁的磁极之间存在着不同的特定关系。直流电动机中电枢磁动势的轴线位置是由电刷位置决定的,电刷具有箝位的功能。发生在直流电动机内的自控变频作用也是箝位效应的直接结果,直流电动机的优良控制性能与箝位效应的存在密切相关。同步电动机只有接至恒频电源才能稳定运转,同步电动机的特征是功角容易变动,在运行中经常出现转子失步,这与它不存在箝位效应有关。无刷直流电动机中的位置传感器代替了电刷的箝位功能,使得其电机本体内同样存在着箝位效应,它完全没有同步电动机的性能行为。

The appearance of brushless DC motor made the difference between DC motor and synchronous motor become confusable. The key to forming two principal classes for both DC motor and synchronous motor lied in the different special relationship among the armature MMF and the DC excited field poles. In DC motor, the locality of axis of armature MMF was determined by the brush position, here the brush possessed a function of clamping. The action of self - controlled variable frequency in DC motor was also a direct consequence of the clamping effect. The excellent controlable performance of DC motor was closely related to the clamping effect in DC motor. The synchronous motor run steady upon condition that the motor was supplied by the power source with constant frequency,which made it become a constant speed motor. The characteristic of synchronous motor was that the power angle was alterable and the rotor was liable to fall out of step, which was related to non - existence of the clamping effect. In the brushless DC motor, the brushes were replaced by the positional sensor but the clamping function was still existed,it made the clamping effect remain the same in the body of brushless DC motor. So the performance and behaviour of synchronous motor were not appeared in brushless DC motor.