US 2003/0155928 A1 · Ground fault detection system and method

Abstract

An AC ground fault detector system for sensing an AC signal indicative of an unintended electrical path between a load driven by a power source and a reference potential comprises a first power conductor coupled to a first terminal of the power source and a second power conductor coupled to a second terminal of the power source. A switching mechanism coupled to the first and second power conductors is operative for alternately connecting a phase of the load with the first and second power conductors according to a predetermined switching rate, whereby, during normal operation, voltages developed at the first power conductor and second power conductor are substantially constant with respect to a reference potential. In the event of an occurrence of the unintended electrical path of at least one phase of the load with the reference potential, time varying voltages are developed at the first power conductor and second power conductor associated with the switching rate. A detector is coupled at an input port to the first power conductor for receiving the voltage or current signal on the first power conductor. The detector includes a processing circuit for processing the received signal and comparing with a threshold value, and an output port for generating an output signal based on said comparison; whereby the occurrence of the unintended electrical path between the load and reference potential causes a change in the voltage or current signal on the first power conductor of sufficient magnitude relative to the threshold value for detection by the detector such that the output signal of the detector is indicative of a detected fault.

Claims20

Dependent claims

An AC ground fault detector system for sensing an AC signal indicative of an unintended electrical path between a load driven by a power source and a reference potential, said system comprising:

a first power conductor coupled to a first terminal of said power source;
a second power conductor coupled to a second terminal of said power source;
a switching mechanism coupled to the first and second power conductors and operative for alternately connecting a phase of said load with the first and second power conductors according to a predetermined switching rate, whereby, during normal operation, voltages developed at the first power conductor and second power conductor are substantially constant with respect to a reference;
and whereby, in the event of an occurrence of said unintended electrical path of at least one phase of the load with the reference potential, time varying voltages are developed at the first power conductor and second power conductor associated with the switching rate;
a detector comprising an input port coupled to the first power conductor for receiving the voltage or current signal on the first power conductor;
a processing circuit for processing the received signal and comparing with a threshold value;
and an output port for generating an output signal based on said comparison;
whereby the occurrence of the unintended electrical path between the load and reference potential causes a change in the voltage or current signal on the first power conductor of sufficient magnitude relative to the threshold value for detection by said detector such that the output signal of the detector is indicative of a detected fault.

5 more elements

A power system for driving a load, said power system comprising:

a power distribution unit for distributing power via first and second power conductors to a corresponding at least one lead of said load according to a switching mechanism which selectively couples a given lead of said load to one of said first and second power conductors at a predetermined switching rate, said first and second power conductors capacitively coupled to one another;
a capacitor having a first terminal coupled to one of the first power conductor and second power conductor, and a second terminal coupled to the reference potential;
and
a detector circuit coupled to the first power conductor, said detector circuit operative for sensing a change in voltage across said first power conductor with respect to the reference potential indicative of an unintended electrical path between at least one said lead and said reference potential, causing said voltage developed across said first power conductor to vary according to the magnitude of the power source, said detector generating a fault signal in response said sensed voltage change exceeding a predetermined threshold;
and
a controller responsive to the fault signal for interrupting power from the first and second power conductors to the load, thereby tending to eliminate the time varying voltage developed at one of the first and second power conductors in response to the unintended electrical path between said least one lead and said reference potential, from being discharged across said capacitor.

3 more elements

Dependencies are inferred from the claim text.

Ground fault detection system and method

Life of this patent

Ground fault detection system and method

Life of this patent

Abstract

Claims20