GB407711A - Improvements in and relating to control systems for the field windings of dynamo-electric machines - Google Patents

Abstract

407,711. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Eaton, J. ; Rosendale Road, Schenectady, New York, U.S.A.) Aug. 22, 1932, No. 23492. Convention date, Aug. 21, 1931. [Class 38 (iii).] Varying electromotive force.-The rates of rise and decay of the field of a generator, such as is used in a Ward-Leonard elevator system are reduced by exciting the field partly from the generator and partly from another source. The generator 10 supplies a load (not shown) and its field 11 is connected to the armature through a resister 12 of such magnitude that the generator fails to self excite. Closure of a switch 14 causes the field 11 to be excited from an exciter 17 through a current-limiting resister 13, most of the current being bye-passed by the armature. As the E.M.F. of the generator builds up, less current is bye-passed through the armature until finally the armature supplies a component of exciting current. When switch 14 is opened, the generator fails to maintain its excitation and the field decays, but at a rate less than that due to its self-inductance alone. The invention is shown embodied in an elevator control system in Fig. 3. The generator 26 supplies the elevator motor 24, and its field 28 is separately excited over reversing contactors 33, 34 and resister excluding contactor 43 controlled by car-switch 41, and is shunt excited through resisters 38<a> and 44. In addition there is provided an exciter machine 36, the field 39 of which is traversed by the load current, and the armature of which is in series with a resister 35 and the field 28 when a switch 37 is closed. The exciter compensates for the I<2>R lower in the load circuit. When the switch 37 is opened, a suicide connection is formed through the exciter 36, resister 40, field 28 and resisters 38 and 35, thus killing the residual magnetism of the generator 26.