초록 ▼

An electrical protection system which uses a ground fault interrupter (GFI) to protect a circuit from (A) ground faults and (B) overcurrents and/or overvoltages. For overcurrent protection, a control element may be coupled in series with the line or return input to the GFI, and a bypass element may

An electrical protection system which uses a ground fault interrupter (GFI) to protect a circuit from (A) ground faults and (B) overcurrents and/or overvoltages. For overcurrent protection, a control element may be coupled in series with the line or return input to the GFI, and a bypass element may be coupled in parallel with the control element and the GFI. In case of an overcurrent, the control element causes current to be diverted through the bypass element, thereby creating a current imbalance in the GFI circuitry causing the GFI to open the circuit. For overvoltage protection, a bypass element (e.g. a varistor) may be coupled between, e.g., the line sense input of the GFI and the return sense input of the GFI. In case of an overvoltage, the bypass element conducts current, thereby creating a current imbalance in the GFI circuitry causing the GFI to open the circuit.

대표청구항 ▼

[ What is claimed is:] [1.] An electrical protection system which can be connected between an electrical power supply and an electrical load to form an operating circuit having a current-carrying line and a return line, and which, when so connected, protects the operating circuit from (A) ground fau

[ What is claimed is:] [1.] An electrical protection system which can be connected between an electrical power supply and an electrical load to form an operating circuit having a current-carrying line and a return line, and which, when so connected, protects the operating circuit from (A) ground faults and (B) overcurrents and/or overvoltages, which system comprises:a. a circuit interruption element, which can adopt a normal state which permits the flow of a normal current, I.sub.NORMAL, in the circuit, or a fault state which permits the flow of at most a reduced current, substantially less than I.sub.NORMAL, in the circuit;b. a comparison element, which,(1) comprises(a) a line sense component which senses the level of a current, I.sub.LINE, in the current-carrying line of the circuit at a line sense point between a line sense input and a line sense output,(b) a return sense component which senses the level of a current, I.sub.RETURN, in the return line of the circuit at a return sense point between a return sense input and a return sense output, and(c) optionally, a passthru sense component which senses the level of a current, I.sub.PASSTHRU, at a passthru sense point in a passthru line, and(2) determines a net effective current, I.sub.COMPARISON , by comparing the levels of I.sub.LINE, I.sub.RETURN and, if the comparison element comprises a passthru sense component I.sub.PASSTHRU, and changes the circuit interruption element from its normal state to its fault state if I.sub.COMPARISON increases from a value less than a predetermined current imbalance value, I.sub.IMBALANCE, to a value more than I.sub.IMBALANCE ; andc. a first bypass element which has a current through it, I.sub.FIRST-BYPASS, which, when the circuit is subjected to an overcurrent and/or an overvoltage, changes and thus causes I.sub.COMPARISON to increase to more than I.sub.IMBALANCE, thereby causing the comparison element to change the circuit interruption element from its normal state to its fault state.