The starting of polyphase squirrel-cage motors

In view of the large size of modern power houses we should change our views regarding the need of starters. The different methods of starting polyphase induction motors are briefly reviewed and the speed torque curves obtained with various types are considered. The effect of starting current upon line voltages, upon the motor and upon connected apparatus is taken up. It is shown that the performance of the compensator is poorer than ordinarily assumed and that the effect upon the line voltage is less with a resistance starter than with a compensator. It is also shown that the heating of the motor is least when thrown directly on the line. The energy required with the various methods is also considered. In large installations it is shown that the considerations involved are radically different. In Appendix A, proof is given that the effect upon the line voltage, is less with a resistance starter than with a compensator. In Appendix B the detailed computations involved in deriving some of the curves are given in full.