GB213272A - Improved method of varying the speed of alternating current electric motors - Google Patents

Abstract

213,272. British Thomson-Houston Co., Ltd., (Assignees of Compagnie Fran- þaise pour l' Exploitation des ProcÚdÚs Thomson-Houston). March 20, 1923, [Convention date]. Alternating - c u r r e n t motors.-An alternating- current commutator motor of the type described and claimed in Specification 25358/11 is coupled mechanically and electrically in series with an induction motor to obtain speed variation over a wide range. As shown, the rotor of an induction motor A supplies the primary winding of the commutator motor B referred to above at slip frequency and the secondary winding of the motor B acts as a, regulating winding according to the brush positions. The combination may be started as two induction motors in series by short-circuiting the stator windings of B or inserting resistances therein, or starting-resistances may be employed between the machines, or a transformer may be employed in this position, or switches mav be introduced between the machines and the induction motor started up separately, and in the latter case the switches may be closed automatically. The machines may be mechanically coupled directly or through gearing.