Abstract
A three-phase synchronous induction motor has a feature of self-starting as a wound-rotor induction motor with a starting resistance enabling starting characteristic superior to that of the traditional brushless synchronous motor with AC exciter. However, the necessity of an excitational DC power supply with a low-voltage and large-current power rating and additional maintaines due to the brushes existence are very disadvantageous.
In this paper, for solution of the above mentioned problems a brushless three-phase synchronous induction motor with two stators and without AC exciter is proposed. The proposed motor has the following mean features:
(1) Superior starting characteristic because of the effects of starting resistance provided at the stator side; the characteristic is as same as that of traditional three-phase synchronous induction motor.
(2) The proposed motor configuration enables the high-voltage and small-current power rating of excitation DC power supply, as a result of the effects of both exciting windings installed in the stator and rotor side.
First, the fundamental configurations and operating principle of the proposed motor are described in detail. Next, for calculation of starting characteristic the equivalent circuits expressed by symmetrical components are proposed. The comparison between the experimental results obtained with a trial machine and the computation results for the starting and load characteristics and their transient ones are also shown. The usefulness of the proposed motor for practical applications and the appropriateness of the equivalent circuits expressed by symmetrical components are investigated too.
