| 摘要 |
There is described a method for retarding a short-circuit induction motor (1) which is driven from a controllabe a.c. inverter (4), the d.c. input of which is connected to a capacitor (6). When retarding the motor (1) the frequency of the inverter (4) is reduced gradually to the frequency which corresponds to desired lower motor speed. At the same time, the signal pattern used to control the controllable switches of the inverter is changed in relation to the pattern of control signals used when not retarding the motor, such that there will occur in the windings of the motor (1) currents of higher frequencies than the frequency corresponding to the speed of the motor and of amplitudes which exceed considerably the amplitudes of such over-frequency currents in the non-retarded operational state of the motor. |
