Abstract: DC power control system for use in an electric vehicular system has DC power supply and power conductors. A meter relay in a control unit enclosure displayably measures the DC current in the conductors and simultaneously establishes an overcurrent limit for tripping out the conductors when the limit is exceeded. Meter calibration and tripping function are testable by a test switch for substituting an adjustable DC test source in place of a conductor meter shunt to the meter relay. Application of DC to shorted power conductors is prevented by preliminary low power DC isolated AC relaying across the conductors. The test switch substitutes a low resistance for the power conductors to also test the AC tripping action. If the power conductors are already energized from a remote power supply, the local power supply is prevented from access by DC responsive relaying during a preliminary time period. After a problem is detected, the control system locks out so as to demand operator attention if the problem persists.

Abstract: Apparatus for protecting the armature of an electric motor against excessive temperatures comprises a resiliently compressible and expansible pad in the armature circuit and composed of thermally sensitive, non-conductive material containing a plurality of conductive particles engageable with one another when the pad is in a compressed condition to establish a conductive path through the pad. The pad normally is maintained in a compressed, conductive condition by resilient force applying means which is of such resilience as to permit expansion of the pad in response to an increase in its temperature and render the pad non-conductive.