Westinghouse Electric Corporation

Roy W Lange

Joseph J Matsko

Raymond O Whitt

This concerns an undervoltage relay device for a circuit breaker system with a time delay feature. Two lines of the electrical system to be protected are monitored by a transformer. The output of which is rectified and provided to a capacitive element which, among other things, filters the signal. The capacitive element may comprise a single capacitor or combination of capacitors. The combination chosen is the function of the amount of time delay desired. If the voltage across the monitor lines drops below a predetermined value, the voltage level across the capacitive element begins to drop accordingly. This decreasing voltage signal is provided by way of a voltage divider to one input terminal of a comparator. The other input terminal of which is maintained at a reference voltage. When the signal voltage drops below the reference voltage, the comparator shift state thus causing an undervoltage relay coil to be deenergized. The armature of the undervoltage relay coil is spring biased so that upon deenergization the armature moves under the influence of the bias thus tripping the circuit breaker. The capacitive element additionally supplies the voltage for the relay coil. The discharge path for the capacitive element is deliberately chosen so that sufficient voltage will be supplied to the relay coil to keep it energized during the time out period of the time delay element, even though the voltage across the lines has dropped to a lower value. The time out is a function of the capacitance of the capacitive element and the resistance of the discharge path. The output of the previously described comparator element is feedback to another comparator element which controls one of the resistive elements of the previously described voltage divider. When the output of the first comparator element changes states, the second comparator element acts in such a way as to change the effect of the resistive element in the voltage divider path thus latching the first comparator into its last obtained state. Another feature is a light emitting diode which is connected in series with the undervoltage relay coil and which extinquishes when the undervoltage relay coil is deenergized, thus providing a positive indication that an undervoltage relay condition exists. Still another feature includes a memory means which extinquishes when the undervoltage relay condition exists and which remains in a disposition of non-illumination. Even if the undervoltage relay condition disappears to provide an indication to an operator that an undervoltage relay condition had occurred previously.

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Brighton Township, Beaver County, PA, United States of America

Roy W Lange