GB576123A - Improvements in the control of compound motors used for rheostatic braking - Google Patents

Abstract

576,123. Control of D.C. motors. GENERAL ELECTRIC CO., Ltd., and CROFT, E. H. May 4, 1942, No. 5974. [Class 38 (iii)] Non-regenerative braking. In a braking system for a vehicle propelled by a D.C. electric motor in which the first motion of a controller has applied rheostatic braking and further motion has applied mechanical fiuid pressure braking, current through a separately excited field is reduced to zero, or a value low enough to prevent undesirable heating, when the speed has dropped' to a predetermined low value. The figure shows electromagnetic contacts 1, 2 and 3 controlling the rheostatic braking. Contactor 1 connects the motor armature to a braking rheostat and contactor 2 gives partial field excitation. Contactor 3 increases field excitation. The final controller step applies mechanical brakes. Relay 10 is closed by the armature e.m.f. or current and opens circuit 8 at a predetermined low speed. Relay 11 is piston-operated to open circuit 9 when mechanical braking is applied. Contactors 1, 2 and 3 are de-energised only when both circuits have opened. Relay 10 may be connected to the armature only when the controller is in a braking position. Relay 10 may be mechanically operated in response to vehicle speed.