Power control of induction motor e.g for driving pump for heating systems

摘要

A power controller of an induction motor C, L1, L2 with an auxiliary winding (1,2) provides power control of the motor by means of a recurring digital word, such as from a ring counter (2). The auxiliary winding L2 has tapping N1, N2 and different power levels of the motor are set by the connection of the auxiliary winding or one of its sub-windings by means of triacs T1-T4. Firstly a coarse adjustment of the power to be output by the motor is effected by the selection of a specified power level and at the same time for the fine adjustment a recurring digital m-bit keying pattern is generated by the ring counter (2) so that the motor is operated alternately with the set power level and with a next higher or next lower power level. This permits automatic power regulation. A microprocessor (3) carries out the coarse adjustment via a drive circuit (1) and at the same time generates the m-bit keying pattern which is stored in the ring counter (2). Alternatively a single triac T1 connected to the main winding L1 may be switched by the drive circuit (1).