| 摘要 |
PCT No. PCT/GB96/01645 Sec. 371 Date Dec. 22, 1997 Sec. 102(e) Date Dec. 22, 1997 PCT Filed Jul. 10, 1996 PCT Pub. No. WO97/04511 PCT Pub. Date Feb. 6, 1997An electrical system has a solid state switch controlled by a circuit emulating the thermal sensor of an electrothermal circuit breaker. A current sensor senses current flowing through the switch. In one arrangement, the current sensor supplies an output to a multiplier, which derives a voltage representative of a current squared, this being supplied to a resistor capacitor circuit having a time constant emulating the thermal sensor. In another arrangement, the output of the current sensor is supplied via an A/D converter to a processor that calculates the difference between heat gain and heat loss of the emulated thermal sensor. The switch is opened when the emulated temperature exceeds a threshold.
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