CONTROL SYSTEM FOR AC INDUCTION MOTORS

A control system is disclosed for connecting the primary windings of a three-phase AC induction motor in a delta-connection at heavy loads and for automatically reconnecting the windings in a wye-connection at light loads to effect energy savings. A power sensor produces a control signal which is directly proportional to the power applied to the induction motor. A differential comparator responds to the control signal and to an adjustable reference signal, representing a preselected power input level, for generating an actuating signal for switching a wye-delta starter between two conditions, one of which effects the wye-connection and the other the delta connection. When the power input is below the preselected level the wye-connection is established, whereas the delta-connection is made when the power input is above the preselected level.