Self‐excited synchronous induction motor

Abstract

AbstractA synchronous‐induction motor, with the features of both a synchronous motor and a wound‐rotor induction motor, far excels other synchronous motors in starting characteristics. However, a major drawback of the synchronous‐induction motor is the need for an excitation power supply with low‐voltage, large‐current power rating. For this reason, its driving equipment becomes large, and increases overall cost.This paper proposes a new synchronous‐induction motor, absent the problems involved in making the motor a self‐excited type. It employs the second‐space harmonic component of armature reaction field to obtain the self‐excitation of the 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 the following advantages: (1) the driving equipment is small, since no excitation power supply is involved; and (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‐kV trial machine.