| 摘要 |
PURPOSE:To realize the constant power control against the load fluctuation by controlling an AC power supply with the average value obtained by converting the AC current value of the AC power supply into the DC current value via a current detector. CONSTITUTION:The output signal of a current detector 11 is proportional to the average value IAVE of a rectified waveform of a pass current of a thyristor 3. Then P=EIS(tON/T) and then IAVE=2X(2<1/2>/pi)ISX(tON/T) are satisfied, where the voltage of a voltage generating source 1 is referred to as E together with the power consumption of a heater 2 as P, an ON period of the thyristor 3 as tON, a total period as T, and the current effective value of the period tON as IS respectively. Then the power consumption P=1.11IAVE is satisfied and therefore the power consumption P is proportional to the average detection value IAVE of the detector 11 as long as the voltage E of the source 1 is kept constant. Then a comparator 7 compares the output signal of the detector 11 with that of a setting volume 6 and a gate pulse generator 8 controls the thyristor 3. Thus the constant power control of the heater 2 is possible against the load fluctuation.
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