JPS5523725A - Starting of three-phase induction motor - Google Patents

Abstract

PURPOSE:To obitain a good wave form for the magnetomotive force of a three- phase induction motor in strarting and in stationary driving, by coupling n-delta- connected second windings (n is a positive integer) among n-Y-connected first windings in starting and by connecting all the windings to one another as a 2n-delta circuit in stationary driving. CONSTITUTION:The three-phase induction motor comprises first windings U1, V1, W1 whose parallel circuit number is n and which have the same number as the pairs of poles per phase and are located at a spacing of 120 deg., and the second windings U2, V2, W2 whose parallel circuit number is n and which have almost the same construction as the first windings and are located among the first windings. In starting the motor, the delta-connected second windings are coupled among the Y-connected first windings and prescribed first and second windings U1 and U2, V1 and V2, W1 and W2 are coupled in series with the terminals R, S, T of a power source to reduce the starting voltage. In stationarily driving the motor, swiches K1, K2, K3 are closed and prescribed first and second windings U1 and W2, W1 and V2, V1 and U2 are connected to each other as a 2-delta circuit.