Patent ID: 6169648
Filing Date: 2001-01-02
Classification: H02H

Abstract:
A motor protection system comprising at least one electrically conductive resistive temperature responsive sensor having an output signal responsive to temperature, a relay coil, an over-temperature protection comparator circuit having first and second inputs and an output changeable between high and low states in response to signals received by the first and second inputs, the output connected to a switch for controlling energization and de-energization of electrical current to the relay coil, the output signal of the at least one sensor coupled to the first input of the comparator circuit so that upon a selected change in temperature of the at least one sensor, the output signal will cause the output of the comparator circuit to change states to de-energize the relay coil, a power supply for the system compatible with both 120 VAC and 240 VAC input voltage including a transformer, the transformer having secondary windings coupled to a full wave rectifier and the full wave rectifier having a DC output, a filter capacitor connected between the DC output and analog ground to provide a ripple voltage rail which is directly related to input VAC voltage, a first voltage regulator connected to the ripple voltage rail for providing a first regulated voltage rail and a second voltage regulator connected to the ripple voltage rail for providing a second, independent, regulated voltage rail, the first regulated voltage rail connected to the relay coil, a voltage divider comprising resistors having a junction connected to the second voltage rail, the junction connected to the second input of the comparator circuit to provide a reference voltage and the at least one temperature responsive sensor being electrically coupled to one of the first and second regulated voltage rails.