A novel method of starting polyphase synchronous motors

This paper records that while some difficulty may ordinarily be experienced in starting up a polyphase synchronous motor simultaneously with the alternator supplying the circuit, the difficulty is greatly reduced if the alternator is of the asynchronous type; and that with small laboratory plant this method of starting is simple in the extreme. Further, if the asynchronous alternator has a wound rotor and an adjustable rheostat in its rotor circuit, then the synchronous motor may be run up to speed by the operation of the rotor rheostat, with the asynchronous alternator running at full speed throughout. A scheme for operating small synchronous motors in a factory with this method of starting is outlined as being technically feasible, though inferior to other methods in general convenience and, therefore, devoid of much commercial utility. Three fields where this method of starting may be of appreciable or occasional use are cited, viz. technical school laboratories, testing-shops of manufacturers, and emergency use by supply authorities.