Variable speed control of asynchronous motor - has three=phase supply provided by commutator driven by low cost motor operating off DC supply

摘要

An asynchronous electric motor is used as the basis of a variable speed drive operating off a d.c. supply. The three phase suppl (T, R, S) for the asynchronous motor (AM) is provided by a commutator (RK) that is coupled to a low cost, low power motor (HM) that is driven by the d.c. output of a mains rectifier (Q). A pole changer (PW) allows the direction of rotation to be reversed. The asynchronous motor speed is changed by varying the commutator motor speed.