GB459546A - Improvements in and relating to rheostatic braking arrangements for electric motors - Google Patents

Abstract

459,546. Master control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. July 11, 1935, No. 19843. Convention date, July 11, 1934. [Class 38.(iii)] Non-regenerative braking.-Rheostatic braking resistance C is eliminated by a controller T, the stepwise advance of which is controlled by a relay S having three coils, one 13 which effects interruption of the power drive for the controller after each step is initiated, another 11 which is energized in accordance with the motor current, and another 12 energized in accordance with the motor voltage, the controller T having contacts controlling the relay coils 11, 12 to give stages of control during which the current and voltage coils act singly, and a further stage during which the current and voltage coils act conjointly, and the relay S operating to withhold power for driving the controller until the current, or the voltage, or the combined effect of the current and voltage, depending on the stage of the control, has fallen below a predetermined value. The relay coils 11, 12 are regulated by resistances 16, 17, 18, and switches 19, 20, so that their strengths are adjusted in dependence on their single or conjoint operation. In order that the braking may be commenced rapidly, a local source of current V, Fig. 6, may be connected across the motor field B, or to an additional motor field, by means of a contactor 37. This contactor is under the control of a relay Y which operates to de-energize the contactor 37, and disconnect the source V, when the braking current attains a predetermined value. The coil 13 of the relay S is energized to prevent movement of the braking controller until the braking current is properly established, by a circuit including contacts of a relay 57, which relay is energized by operation of the relay Y, and opens its contacts after a time interval. The relay Y after operation is sufficiently energized to be ineffective in controlling the controller servomotor, but it may be maintained in an operated position by an additional coil energized when the relay 57 operates. The master controller Z may have a series of positions in which it places a limit on the extent of movement of the braking controller T, and an " advance " handle may be provided controlling a relay by means of which the controller T may be advanced one notch at a time independently of the control exerted by the relay S. The braking resistance C may be arranged in two sections, one on each side of the motor armature.