Three-phase supervisory circuit
OwnerStephen Liscinksyinventor
Life of this patent
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Abstract
An apparatus and method for detecting fault conditions in an input AC power signal. A three phase supervisory circuit is used to detect the fault conditions and comprises first, second and third sensing circuits for detecting a voltage level for respective phases of the AC power signal. The three phase supervisory circuit compares the voltage levels to a threshold value. A delay circuit delays operation of the sensing circuits for a predetermined period of time. An activation circuit for receiving indication signals from the sensing and delay circuits is also used. The indication signals are indicative of whether the predetermined period of time has elapsed and the three voltage levels of the three phases have met the threshold value.
Claims16
A three phase supervisory circuit for detecting fault conditions in an input AC power signal, comprising:
- a first sensing circuit for detecting a voltage level for a first phase of said AC power signal and comparing said voltage level of said first phase to a threshold value;
- a second sensing circuit for detecting a voltage level for a second phase of said AC power signal and comparing said voltage level of said second phase to said threshold value;
- a third sensing circuit for detecting a voltage level for a third phase of said AC power signal and comparing said voltage level of said third phase to said threshold value;
- a delay circuit for delaying operation of said sensing circuits for a predetermined period of time;
- and
- an activation circuit for receiving indication signals from said sensing and delay circuits, said indication signals indicative of whether said predetermined period of time has elapsed and said voltage levels of said phases have met said threshold value.
A method for detecting ground fault conditions in an input AC power signal via a three phase supervisory circuit, the method comprising:
- detecting a voltage level for three phases of said AC input power signal;
- comparing said detected phase voltage levels to a threshold value;
- delaying operation of said three phase supervisory circuit for a predetermined period;
- and
- providing results from said steps of comparing and delaying to an activation circuit.
Dependencies are inferred from the claim text.