Overcurrent protection device and arrangement

An electrical circuit, comprising an electrical power supply, a load, and a protection system coupled between the power supply and the load, the protection system protecting the circuit from overcurrents and comprising:

• a. a circuit interruption element which
• (1) has a normal state which permits the flow of a normal circuit current, I.sub.NORMAL, to pass through the system, and
• (2) has a fault state which permits the flow of at most a reduced current, I.sub.REDUCED, substantially less than I.sub.NORMAL ;
• b. a first control element which
• (1) is coupled in series between the power supply and the load, and
• (2) is functionally linked to the circuit interruption element so that when the current through the first control element increases from I.sub.NORMAL to a relatively high current, I.sub.FAULT, the first control element can convert the circuit interruption element into the fault state;
• and
• c. a second control element which
• (1) is coupled in parallel with the circuit interruption element, and
• (2) is functionally linked to the circuit interruption element so that if the circuit interruption element is converted to the fault state, the second control element can cause the circuit interruption element to remain in the fault state as long as the current through the second control element is at least I.sub.REDUCED ;
• with the parallel combination of the circuit interruption element and second control element coupled in series with the first control element.

An electrical protection system which can be coupled between an electrical power supply and an electrical load to form an operating circuit, and which when so coupled protects the circuit from overcurrents, which system comprises:

• a. a circuit interruption element which
• (1) in use, is coupled in series with the power supply,
• (2) has a normal state which permits the flow of a normal circuit current, I.sub.NORMAL, to pass through the system, and
• (3) has a fault state which permits the flow of at most a reduced current, I.sub.REDUCED, substantially less than I.sub.NORMAL ;
• b. a first control element which, in use, is coupled in series with the circuit interruption element;
• and
• c. a second control element which in use, is coupled in parallel with the load;
• wherein
• i. the second control element is functionally linked to the circuit interruption element so that, while the voltage across the second control element is a normal voltage, V.sub.NORMAL, the second control element can cause the circuit interruption element to be in its normal state;
• and
• ii. the first control element is functionally linked to the circuit interruption element so that when the current through the first control element increases from I.sub.NORMAL to a relatively high current, I.sub.FAULT, the first control element can convert the circuit interruption element into the fault state.

An electrical circuit, comprising an electrical power supply, a load, and a protection system coupled between the power supply and the load, the protection system protecting the circuit from overcurrents and comprising:

• a. a circuit interruption element which
• (1) is coupled in series with the power supply,
• (2) has a normal state which permits the flow of a normal circuit current, I.sub.NORMAL, to pass through the system, and
• (3) has a fault state which permits the flow of at most a reduced current, I.sub.REDUCED, substantially less than I.sub.NORMAL ;
• b. a first control element, coupled in series with the circuit interruption element;
• and
• c. a second control element, coupled in parallel with the load;
• wherein
• i. the second control element is functionally linked to the circuit interruption element so that, while the voltage across the second control element is a normal voltage, V.sub.NORMAL, the second control element can cause the circuit interruption element to be in its normal state;
• and
• ii. the first control element is functionally linked to the circuit interruption element so that when the current through the first control element increases from I.sub.NORMAL to a relatively high current, I.sub.FAULT, the first control element can convert the circuit interruption element into the fault state.

A relay comprising:

• a. a set of contacts having
• (1) an deenergized position in which the contacts are one of open or closed, and
• (2) an energized position in which the contacts are the other of open or closed;
• b. a magnetic core;
• c. a first relay coil wound around the magnetic core;
• and
• c. a second relay coil wound around the magnetic core;
• wherein one relay coil comprises T times the number of turns which the other coil comprises, where T is at least 10.