GB776937A - Improved circuit arrangement for braking direct current motors - Google Patents

Abstract

776,937. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. July 22. 1955 [Aug. 12, 1954], No. 23464/54. Class 38(3) A braking circuit for a direct-current series motor 1 comprises an auxiliary field winding 3 which is automatically connected to the armature of the motor so as to produce flux in the same direction as the main series field, winding 2 when the external supply to the motor is interrupted. During motoring operation, contacts 12c are closed and contacts 12a, 12b, are open so that, assuming contacts 4, 6, are closed for operation of the motor in one direction, relay coils 8<SP>1</SP>, 10<SP>1</SP>, are energized from the supply-lines to close contacts 8, 10. When the supply is interrupted the opening of the contacts 8, 10. is delayed sufficiently to allow the energization of coils 8<SP>1</SP>, 10<SP>1</SP>, to be transferred from the external supply to that due to the generated voltage of the armature, the circuit for the relay coils being completed through contacts 12b and 8a. Thus, the contacts 8, 10, remain closed and the winding 3 is energized through contact 12a so that the flux produced by the auxiliary field winding maintains the generated voltage, dynamic braking being established by connecting resistor 13 across the armature of the motor. If contacts 5, 7, are operated for reversing the motor, then the connections to the winding 3 are also reversed by closure of contacts 9, 11. In a modification the auxiliary field winding is seriesconnected.