GB370532A - A system for positively controlling the rates of rise and decay of the magnetism of an electromagnet or of an electric generator - Google Patents

Abstract

370,532. Control of D. C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Whiting, M. A.; 1698, Rugby Road, Schenectady, New York, U.S.A.) Jan. 21, 1931, No. 2072. Convention date, Jan. 21, 1930. [Class 38 (iii).] Varying electromotive force.-The growth and decay of excitation of an inductive winding 10, Fig. 4, such as the winding of an electromagnet or the field winding of a Ward-Leonard generator, is prolonged by a separately excited machine 14, having a flywheel 17, being connected in shunt to the winding, which is in series with a resistance 11. Briefly, upon closing switch 18 only a very small potential difference is applied to the winding 10 as the machine 14 is stationary. As the latter accelerates its back-E.M.F. increases with consequent increase of the excitation of the winding 10. The Specification gives a mathematical analysis of the action and shows that with certain energy storage relationship between the flywheel and the winding, it is possible to obtain an oscillatory growth or decay. A lift control system is shown in Fig. 1. The field 31 of the generator 28 is shunted by the control machine 41 having the flywheel 42. Normally the controller 37 is thrown from the "off" position to one of the "full-on" positions, thereby closing upward or downward contactors 33, 34, excluding field resistance 35, closing contactor 39 to withdraw a brake 38, and closing contactor 46 to exclude a resistance 45 from the armature circuit of the machine 41. The field 31 excites gradually with consequent gradual acceleration of the motor 26. When the controller 37 is returned to its "off" position, both contactors 39, 46 are maintained closed by auxiliary windings until the machine 28 has ceased to generate. In the first two positions of the controller 37, the contactor 46 does not close, so the lift may be levelled without delay being imposed upon the growth of excitation of the field 31. Specification 303,151, [Class 38 (iv), Electric supply and transmission systems &c.], is referred to.