A Slef-Excited Synchronous-Induction Motor

Abstract

A synchronous-induction motor has a feature of both synchronous motor and wound-rotor induction motor, and far excels other synchronous motors in starting characteristic. However, a major drawback of the synchronous-induction motor is to need an excitation power supply with a power rating of low-voltage and large-current. For this reason, its driving equipment becomes large, and increases the overall cost.
In this paper we propose a new synchronous-induction motor, which has no problem described above by making the motor of self-excited type. It employs the second space harmonic component of armature reaction field to obtain the self-excitation of field system, and installs a harmonic winding, which is used for extraction of an excitation power, in the rotor. This new self-excited motor has following advantages. (1) The driving equipment is small, since no excitation power supply is involved. (2) Due to the effect of the series characteristic by which the field current varies in proportion to the load current automatically, the motor can be operated with a good power factor.
In the present paper the structure and operating principle of the new motor are explained, and the basic characteristics are also investigated by means of a simple analysis and experimental results with a 1.5-kW trial machine.