Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Reexamination Certificate
2000-06-26
2003-12-30
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
C361S093100
Reexamination Certificate
active
06671144
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a circuit breaker circuitry for protecting a power source from ground faults.
BACKGROUND OF THE INVENTION
Many devices known in the art are useful for protecting power sources from ground faults. Ground faults occur when grounded conductors come into contact with electrical circuitry, causing an excessive current flow in that circuitry. As a result, power supply can become overloaded, and the load that the power supply is meant to power ends up receiving little or no current at all.
The existing devices for protecting power sources from ground faults use thermal sensors, magnetic sensors, or current sensors to detect ground faults. For these devices, it is necessary to select and calibrate their sensors to accommodate the current drawn by the load for proper operation, making the existing fault protection devices load dependent. The process of selecting and calibrating particular sensors to the current drawn by the load is time consuming and expensive. Furthermore, these sensors must be recalibrated when the current drawn by the load changes significantly or if a different load is used.
Accordingly, there exists a need for a ground fault detection and protection device which operates independently of the load so that no calibration of the sensor is needed and is cost-effective to construct.
SUMMARY
The present invention relates to a circuit breaker circuitry for protecting a power source from ground faults. More specifically, the circuit breaker circuitry operates independently of the load to which the power source is connected. In addition, the preferred circuit breaker circuitry includes a time delay circuitry to prevent false detection of ground faults resulting from current spikes that may occur when the power supply connects to the load.
Preferably, the circuit breaker circuitry includes a control relay that connects a power source to its load. The control relay is powered by the power source through a circuit breaker so that, when the circuit breaker overloads and opens, the control relay loses power and severs the connection between the power source and the load.
Preferably, the circuit breaker circuitry also includes a sensor diode that detects ground faults by monitoring the voltage drop across the control relay. The sensor diode connects to the power supply side of the control relay through a time delay relay and the circuit breaker and connects directly to the load side of the control relay. When a ground fault occurs in the circuit, the ground fault draws a high current that causes the potential drop across the control relay to exceed the forward voltage of the sensor diode, activating the sensor diode. As a result, the sensor diode begins to conduct current through the circuit breaker, causing the circuit breaker to overload and open. Consequently, the control relay loses power and disconnects the power source from the load as well as the ground fault.
After removing the ground fault and manually resetting the circuit breaker, power returns to the control relay and the connection between the power source and the load is restored. However, the time delay relay delays the connection between the sensor diode and the power supply side of the control relay. This delay functions to shield the sensor diode from any current spikes that may occur when connecting the power source to the load so that no false detection of ground faults can occur.
Preferably, the circuit breaker circuitry also includes a fault protection condition indicator for indicating whether the circuit breaker circuitry is working properly.
REFERENCES:
patent: 3634729 (1972-01-01), Hendry
patent: 3766435 (1973-10-01), Childers
patent: 3968410 (1976-07-01), Graham
patent: 3992650 (1976-11-01), Iwasa et al.
patent: 4068149 (1978-01-01), Wuchinich
patent: 4079211 (1978-03-01), Janssen
patent: 4121122 (1978-10-01), Pokrandt
patent: 4412267 (1983-10-01), Hansen
patent: 4580186 (1986-04-01), Parker et al.
patent: 4860154 (1989-08-01), Fazlollahi
patent: 4878034 (1989-10-01), Gross et al.
patent: 4947278 (1990-08-01), Nichols, III
patent: 4949214 (1990-08-01), Spencer
patent: 4992904 (1991-02-01), Spencer et al.
patent: 5055703 (1991-10-01), Schornack
patent: 5237480 (1993-08-01), Dara
patent: 5424894 (1995-06-01), Briscall et al.
patent: 5532898 (1996-07-01), Price
patent: 5576615 (1996-11-01), Marshall et al.
patent: 5606482 (1997-02-01), Witmer
patent: 5627411 (1997-05-01), Bochenek
patent: 5657195 (1997-08-01), Rault
patent: 5659894 (1997-08-01), Bayruns et al.
patent: 5691869 (1997-11-01), Engel et al.
patent: 5825602 (1998-10-01), Tosaka et al.
patent: 5864456 (1999-01-01), Connor
patent: 5867358 (1999-02-01), Campbell
patent: 5883578 (1999-03-01), Roberts et al.
patent: 5933311 (1999-08-01), Chen et al.
patent: 5946179 (1999-08-01), Fleege et al.
patent: 5986860 (1999-11-01), Scott
patent: 5999384 (1999-12-01), Chen et al.
patent: 6034446 (2000-03-01), Kowalski et al.
patent: 54-147875 (1979-11-01), None
Quong, Resettable electronic fuse consists of SCR and relay; Sep. 15, 1977, Electronics, vol. 50, No. 19, p. 117.
Langford Joseph Andrew
Osborne Gregory Warren
Leja Ronald W.
Pennie & Edmonds LLP
Premier Aviation, Inc.
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