Open circuit device and method of induction motor

[0008] figure 1 Shows the R, S, T, N terminals of a three-phase network, and the delta-connected field windings 1, 2, 3 of a squirrel-cage motor. To start the motor, the S end is connected to the N end through the key switch 13 through the key stop switch 14, the key emergency switch 15, the contact 23 of the open circuit current relay 28, and the coil 7 of the running current relay 27, and the working current relay pulls in. Among them, the contact 8 is opened, and the contacts 9, 10, 11 connect the phase voltages from R, S, T to terminals 6, 5, 4 of the field windings 1, 2, 3, and the coil 7 passes through the contacts 14, 12 , 15, 23 get the maintenance current. To open the motor, the maintenance current circuit of the working current relay 27 must be cut off through the button stop switch 14 or the button emergency switch 15, so that the working current relay 27 is released, and the contacts 9, 10, 11, 12 are disconnected to cut off the motor. The working current, then t...