The automatic-start polyphase induction motor

A paper presented by the author at the 314th meeting of the American Institute of Electrical Engineers, held in St. Louis, on Oct. 19, 1915, covers the characteristics, electrical and mechanical design of the repulsion-start, single-phase induction motor. The present paper similarly deals with the automatic-start, polyphase induction motor which has very similar characteristics. This automatic-start polyphase motor has come into considerable prominence during the last few years. A large number of motors of this type is now being built and placed in service. While there is considerable literature on the subject of induction motors, there is little information available on this type of motor which in reality is a combination of two types of motors, a very high-resistance-rotor induction motor and a low-resistance-rotor induction motor. The motor is converted from a high-resistance-rotor motor at starting, to a low-resistance-rotor motor running by means of an automatic switch. The objects of this paper are: 1. To set forth the general characteristics of this type of motor as compared with other standard types of motors. 2. To outline a commercially practical method of studying electrical design of existing motors, and predetermining the electrical design of proposed motors. 3. To discuss the mechanical design.