Switching drive of induction motors

Recent developments in semiconductors lead to new possibilities of motor control in general and of the induction motor in particular. The latter type of motor, although the most simple in construction and therefore the most widespread in use, does not lend itself easily to speed control and feedback arrangements. The paper shows that electronic control by means of semiconductors of the thyratron type is easily adaptable to speed-control requirements. This type of control, based on switching currents by semiconductor devices, is applied first to the stator circuit and secondly to the rotor circuit. In the former case a squirrel-cage motor can be used, but the rotor control circuit will show certain advantages.