About induction melting furnace main protected content, set causes and methods

Protected name	Protection reason and protection method
The cooling water temperature is too high	When the outlet temperature of the cooling water exceeds the specified allowable value, it is easy to cause scale, or even vaporize the water, causing an accident. Therefore, a charged water temperature gauge can be installed at the outlet of each water-cooling pipeline. When the water temperature at the exit of any cooling water circuit exceeds the allowable value, an alarm signal will be issued
Cooling water pressure drops	When the water pressure of the cooling water is lower than the required number, the cooling conditions will be destroyed. On the main cooling water inlet pipe, there is a water pressure gauge with a live contact. When the water pressure drops below the allowable value, an alarm signal is issued and the sensor power supply circuit is cut off
Over current, short circuit protection	Install a differential protection over-current relay, when the main circuit has an over-current and short-circuit accident, the main circuit is cut off and an alarm signal is issued
Under voltage protection	In front of the main circuit closing contactor, an undervoltage relay is connected. When the main circuit is de-energized, the main circuit closing contactor will automatically trip, and there will be an accident signal indication. When the next call comes, reclose
Phase C open phase protection	At the outlet end of the balancing device, there is a C- phase open-phase protection relay. When phase C is cut off, the main circuit is immediately cut off, and there is a signal indication to prevent resonant current in the balance reactance and balance capacitor circuit, which will burn out the balance reactor and capacitor
Protected name	Protection reason and protection method
Limit the protection of the main circuit closing current	In the induction furnace, there are a large number of compensation capacitors and balancing capacitors, which will generate a large inrush current when closing. Therefore, the main circuit is closed twice. First close the starting contactor with resistance, then close the working contactor, and cut off the resistance
Transformer oil temperature indication and gas protection	The electric furnace transformer has an oil temperature indicator to monitor the oil temperature. Gas protection is also installed on the larger capacity electric furnace transformer ( above 800KVA ). When a fault occurs and the Buchholz relay will act, the power supply circuit will be cut off and an alarm signal will be issued
Capacitor internal overcurrent protection	Phase-shift capacitors and intermediate-frequency electric heating capacitors below 3000V power frequency are all connected with over-current fuse protection inside. When any group of capacitors fails, the group will be automatically cut off.
Crucible leakage furnace and main circuit grounding protection	Equipped with crucible alarm device. When the crucible leaks out of the furnace or the main circuit is grounded, the power is cut off and an alarm signal is issued
Overvoltage protection	Install an over-voltage absorber on the secondary side of the transformer to prevent operating over-voltage, transformer primary and secondary side breakdown and over-voltage caused by lightning strikes
Capacitor discharge protection	After the main circuit is powered off, the capacitor must be discharged for safety. The capacitor is automatically discharged through the load, and the variable capacitor is automatically placed in the resistance circuit for discharge