Motor winding leakage monitor
AssigneeAutomeg, Inc.
InventorsJoseph G. Horvath, James C. Miller
Life of this patent
Estimating the term…
Abstract
A low voltage power supply powers a high impedance, high voltage dc supply. An electronic switch serves to automatically connect the high voltage output to the windings of a motor when the motor is non-operating. A lead connects from the frame of the motor to a sense resistor connected to the high voltage system ground. A plurality of variable threshold comparators is connected across the sense resistor. Leakage of the motor windings insulation results in a current flow through the sense resistor producing a voltage drop proportional to the leakage. Each comparator is adjustable to produce an indication of a value of leakage resistance at which the comparator produces an output.
Claims9
Apparatus for automatically monitoring the insulation leakage resistance of two or more electric motors, each of said motors controlled by a respective contactor, comprising:
- a high-voltage direct current power supply having a system ground and a high-voltage output;
- switching means connected between said high-voltage output and electrical winding of each of said motors, said switching means having control means connected to the contactor of each of said motors, said control means responsive to the state of said contactor for controlling said switching means to apply said high-voltage output to the motor windings of a non-operated one of said motors only when at least one other of said motors is operating;
- a sense resistor connected from the frames of said motors to said system ground;
- and
- comparator means connected across said sense resistor for producing an indication when a voltage across said resistor due to flow of leakage current exceeds a preselected value.
A device for monitoring the leakage resistance of an electric motor or the like only when the motor is non-operated, said motor having a control switch, comprising:
- a high voltage direct current power supply having a system ground and a high voltage output;
- a sense resistor connected from the motor frame to said system ground;
- electronic switch means connected between said high voltage output and the windings of said motor, said switch means having a control input connected to said control switch for causing closure of said electronic switch means when said control switch is open and for causing opening of said electronic switch means when said control switch is closed;
- and
- a comparator connected to said sense resistor for producing an output indication of leakage current flowing through said sense resistor when such current exceeds a preselected magnitude.
Dependencies are inferred from the claim text.