GB907209A - Improvements relating to control systems for electrically-propelled vehicles - Google Patents

Abstract

907,209. Control of D.C. motors. WITHNELL, A. C. March 28, 1961 [March 30, 1960], No. 11159/60. Addition to 836,900. Class 38 (3). The control system for the motor of a battery vehicle described in the parent Specification is modified to include a " dead man's handle." This comprises a biasedoff switch on the steering wheel or tiller, release of which causes the cutting off of power to the motor and preferably the application of rheostatic braking, at least when the vehicle is moving forwards. Mechanical wheel brakes may also be applied by an electrical actuator. As shown, release of the switch opens relay contacts DMH, de-energizing relay MPR, contacts on which are included in the energizing circuit of contactors R+ and RR. These contactors are in the motor supply circuit and two are used to minimize the chance of mal-operation through sticking. The motor supply is thus cut off, and further contacts on relay MPR, and also interlock contacts RRa on RR, close to energize rheostatic braking contactor B. Contactor R+ has auxiliary contacts R+a in the energizing circuit of the resistor contactors R2 ... R4 which are thus opened to prevent the rheostatic braking, e.g. from full speed, being too severe. Contactor R1 remains operable to allow two degrees of braking, according to speed conditions obtaining when the dead man's handle was released. The braking will be effected regardless of the direction of rotation of the motor, but a simpler circuit is described wherein rheostatic braking occurs automatically only if the motor was. running forwards. Upon re-closure of the dead man's handle switch the motor will not restart until the controller is returned to the zero speed position, since only then will relay MPR be energized. An overload cut-out OL has also been introduced in the present arrangement.