| 摘要 |
<p>PURPOSE:To prevent generation of stripe patterns, which appear on a steel plate during induction heating, by changing the phase cyclicly by the output of a voltage detection circuit. CONSTITUTION:A phase control circuit 8, which controls the phase of a detected voltage signal cyclicly, is provided in the middle of a voltage detection circuit to which the detected voltage signal is input from output side of a high frequency inverter 3. The phase control circuit 8 consists of a phase delay part 5, a phase advance part 6, and a delay phase control part 7. When the delay phase control part 7 is off, the quantity of phase control is zero, so the negative voltage is inverted with the resonant frequency of a load circuit 14, and the load currents of the above resonant frequency are let flow to the load circuit 14. On the other hand, when the phase control part 7 is on, the quantity of phase control becomes advance, and it performs commutation quickly as compared with when the quantity of phase control is zero, so the voltage phase inversion time after commutation becomes short, and frequency becomes high. Hereby, the frequency of the high frequency power source can be changed.</p> |
