Intermediate frequency induction melting furnace maintenance failure example: inverter circuit can not start or start difficult
Fault phenomenon
The inverter circuit of the IF power supply cannot be started or start difficult.
Fault analysis and processing
The main reason why the inverter circuit of the IF power supply cannot be started or started is as follows.
(1) Short circuit between induction coils. If the induction coil does not cool well for a long time, the insulation is broken and a short circuit between turns is caused. Conductive materials such as dust and scale on the induction coil can also cause short-circuit between turns. When the intermediate frequency power supply is started, the ignition phenomenon occurs, and frequent ignition may cause the induction coil to break down. In this case, the surface of the induction coil should be cleaned, brushed with insulating paint or asbestos board.
(2) The induction coil is short-circuited to the arc furnace casing. The induction coil housing is loose and there is too much ash in the furnace; the induction coil is discharged through the furnace base. In this case, the induction coil should be reinforced to remove dust.
(3) The copper busbar connected to the induction coil at the intermediate frequency output is short-circuited. If there is a foreign object or the copper is not fixed, it may cause a short circuit between the copper rows.
(4) The capacitor case is short-circuited to the ground. At this time, it should be checked whether there is water leakage, whether the capacitor base is too much gray, and whether the ceramic base of the capacitor is missing.
(5) The water-cooled cable is disconnected, and the copper bus that is output to the load is blown.
(6) Check if the current transformer insulation is damaged; remove the current transformer to check whether the insulation is good; use a multimeter to measure whether the coil is blown, and check if the wiring sequence is correct. If both are normal, check whether the potentiometer of the current signal adjustment is too small. The amplitude of the output current signal should be re-adjusted.
(7) Check if the inverter circuit's inverter angle is too small. If it is too small, adjust the inverter angle; if it is normal, check if the current polarity is reversed. If not, check the inverter thyristor for a trigger pulse. If it is normal, check the inverter thyristor for damage. If it is damaged, replace it with a thyristor of the same type and specification.
