Abstract: A heater element for use in a circuit breaker whose initial shape can be varied to achieve various trip ratings for different circuit breakers. The material composition of the heater element and the bimetal strip indirectly heated by the heater element are kept the same. The electrical resistance presented to current passed through the heater element is varied by varying the shape of the heater element. The shape of one heater element relative to another heater element varies according to one geometric parameter. The geometric parameter may be surface geometry, thickness, or cross-sectional area.

Abstract: A high voltage, current limiting device is connected in series with a high voltage power source and a protected load to interrupt current for an over-current condition [Typically 50 kA]. The current limiting device includes a current sensor/isolator and a switch connected in series. A current limiter, which may include a fuse or polymer current limiting material, is connected in parallel to the current sensor/isolator. The current sensor/isolator includes a pair of electrically insulated supports secured to a plurality of support rods to maintain the insulated supports at a predetermined fixed spacing to support an expulsion fuse. The expulsion fuse link includes a pair of copper conductors of adequate current carrying capability that are attached to ends of a main weak link fuse. A pair of coil springs hold the weak link fuse under tension to repel the conductors apart when the weak link fuse melts open during an over-current condition.

Abstract: A thermally actuated switch having a bi-metal switch arm carrying a contact, a cooperating contact, a heating resistor and a holding resistor. The switch is enclosed in a sealed housing and circuit connections extend from the switch contacts, heating resistor and holding resistor to the exterior of the housing. The heating position thereby closing or opening the switch contacts, depending on whether the contacts are normally-open or normally-closed. After switch actuation, the heating resistor continues to supply heat to the switch arm to hold the arm in its actuated position. The connections from the heating and holding resistors to the exterior of the housing enable the connection of external variable resistors in circuit with the heating and holding resistors whereby the time required for the switch to actuate and the time to switch remains actuated may each be varied.

Abstract: A discharge lamp starting device employing a thermal switch which comprises main and auxiliary bimetal electrodes respectively thermally bendable in the same direction, and an auxiliary heater for heating the auxiliary bimetal electrode in addition to a main heater for the main bimetal electrode. The auxiliary heater is energized to heat the auxiliary electrode upon a starting failure specifically when the discharge lamp is to be lighted again immediately after its extinguishment, whereby the auxiliary electrode is forced to bend toward the main electrode and a re-closing of the thermal switch and eventual lamp starting can be accelerated.