| 摘要 |
PURPOSE:To prevent propagation of noise, by a method wherein a cycle control unit and a contactless switching unit driven by this output are provided as independent units, and both units are connected by a signal transmission circuit. CONSTITUTION:Temperature of an electric furnace is detected by a temperature measuring member 26, and ON/OFF control of a thyristor switch 17 is performed by control signal from a temperature adjuster 27, and power of a power source 14 is supplied to a heater 13 of an electric furnace 25. This power control device is constituted by a cycle control unit 30 comprising an input circuit 28 and a cycle control circuit 29, and a contactless switching unit 31 having a thyristor 17 and a zero cross trigger circuit 15 to output gate signal thereof for switching energizing current to the heater 13 independently. Both units 30, 31 are connected by lead wires 21, 22, and coupled by a phototransistor 15. In this constitution, the electric furnace 25 is controlled to a prescribed inside temperature by control signal based on difference between a detecting temperature and a setting temperature.
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