| 摘要 |
PURPOSE:To prevent the generation of noise and vibration at the time of change- over when a pole changing type induction motor driving a load independent of the revolving direction like reciprocating compressor, etc., is operated slowing down the speed by a method wherein small number poles are converted to large number poles and the revolving direction is reversed. CONSTITUTION:When a pole changing type induction motor is to be driven in dipole operation, R, S, T phases of a power source are shunted into two circuits at points U1, V1, W1 of the motor to be operated having double star circuits by closing contacts X1, X3 and opening a contact X2. When the motor is to be driven in quadrapole operation, the number of poles is converted by closing the contact X2 and opening the contacts X1, X3 and the motor is driven in slow speed and the revolving direction is reversed. Therefore when the motor operating at the operation point D is changed-over from the dipole operation to the quadrapole operation, the quadrapole operation is made to start at the point E' where the motor has the same direction of torque, the number of revolution reduces along the curve IV and becomes to stable at the point of intersection G with the load torque curve L, so that noise and vibration does not generated and the life of machine can be enlarged. |
