Universal motor drive e.g. for washing machine - has triac-switched field windings supplied with AC during alternate half-cycles for duration corresp. to speed of motor

摘要

The armature winding (A) is wired to the DC side of a diode bridge rectifier (B). The AC mains supply (L,N) is connected to the opposite diagonal of the bridge by a pair of triac-switched field windings (F1,F2) in parallel. The triacs (T1,T2) are gated during opposite half-cycles by an electronic speed controller (E) according to the desired direction of rotation, with speed controlled by the triac firing angle. USE/ADVANTAGE - E.g drum of washing machine. Diodes with lower blocking voltage can be used, and field windings can serve as commutation chokes.