1。 The induction furnace works normally at low power, and over-current or over-voltage protection acts when the power rises. The following tests can be performed:
① Whether the silicon controlled elements of the main circuit are aged and their current and voltage tolerance are reduced;
② Whether the thyristor resistance capacitance absorption circuit of the main circuit is in poor contact, damaged or broken.
③ Whether the turn to turn insulation of reactor and load inductor is good.
④ Check whether the cooling water circuit is blocked, whether the water temperature is too high, and whether the water pressure is too low.
⑤ Whether the withstand voltage of load compensation capacitor drops.
⑥ Whether the anti-interference performance of the control system decreases (especially the thyristor trigger circuit), because the interference will increase with the increase of intermediate frequency power, and the over-current or over-voltage protection may malfunction.
⑦ Whether the angle before triggering the inverter circuit is too small. When the current rises, the over-current protection will act due to the unsuccessful commutation.
⑧ Whether the thyristor waveform of the main circuit is normal (whether the output of the rectifier circuit is in phase loss, and whether the output of the inverter circuit is in phase loss).
⑨ Whether the insulation to ground of the main circuit drops.
⑩ Whether the setting value of over-current and over-voltage changes.
2。 Both DC voltage and IF voltage can deliver rated value, while DC current is very low, and rated IF power cannot be delivered when Ud reaches the maximum value, which can be handled according to the following conditions:
① The leading angle of inverter triggering is set improperly.
② The load induction furnace and compensation capacitor are improperly matched, and the equivalent impedance of load current is too high.
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