Maintenance method of intermediate frequency furnace rectifier circuit
After the main frequency furnace starts the main circuit, the DC voltmeter has no response, and there is no response to start the inverter. The panel meter has no indication except the frequency meter. Such faults are generally caused by the rectifier bridge not working and no DC output. The causes of such failures are generally:
(l) The common ground wire (line 70) of the intermediate frequency furnace rectification trigger pulse output is in poor contact or open circuit, causing the rectifier thyristor to have no trigger pulse and not working.
(2) More than three boards of the induction melting furnace trigger board are damaged, resulting in no output of the rectifier bridge.
(3) The intermediate frequency furnace rectifier power supply board or power amplifier power board is damaged, so that the rectifier trigger board has no pulse output, resulting in the rectifier thyristor not working. At this time, the rectifier voltage regulator voltmeter and ammeter in the cabinet usually have no indication or the rectifier power amplifier ammeter has no indication.
The intermediate frequency furnace runs abnormally.
When the intermediate frequency furnace is working, the filter reactor emits dull irregular vibration sound, and the startup is difficult, the work is unstable, and the overcurrent is prone to occur.
Protection action, there is a large current impact sound when moving. The reason for such failures is generally due to the presence of the furnace at the load end.
Completely shorted. When the furnace body is not completely short-circuited, the load will be aggravated, the current will be unstable, and the flow will be easy. Measuring the waveform of the inverter thyristor with an oscilloscope reveals that the waveforms are scattered, overlapped, and the jitter is severe. Causing the furnace to be incomplete
Short circuits generally have the following conditions:
l) The yoke and the induction coil have incomplete short circuit or arcing phenomenon, and when the arc is severe, a large howling sound is emitted.
2) The tightening bolt insulating gasket of the hearth yoke breaks down so that the yoke is short-circuited with the outer casing, and there is a strong arc when not completely short-circuited. The short circuit of the yoke and the outer casing is equivalent to the addition of a short-circuited secondary side coil to the induction coil, so that the load of the induction coil is increased.
3) The induction coil is short-circuited with the molten iron. When the short circuit is severe, the intermediate frequency intermediate frequency furnace cannot be started.
4) The through-bolt insulation sleeve of the H1 yoke breaks down, causing an inductive loop, forming a theoretical short-circuit secondary side, which increases the load on the induction coil.