The role of water-cooled cables
The function of the water-cooled cable is to connect the medium frequency power supply and the induction coil. It is formed by twisting each diameter Φ0.6-Ф0.8 copper wire. For a 500 kg medium frequency electric furnace, the cable cross-sectional area is 480 square millimeters, and for a 250 kg medium frequency smelting electric furnace, the cable cross-sectional area is 300 to 400 square millimeters.
The outer hose of the water-cooled cable adopts a pressure rubber hose with a pressure resistance of 5 kg, which is filled with cooling water. It is a part of the load circuit. It is subjected to tensile and torsion forces during operation. The connection is broken.
The breaking process of the water-cooled cable generally involves cutting off most of the parts first, and then quickly breaking the unbroken part during high-power operation. At this time, the medium frequency power supply will generate a very high overvoltage. If the overvoltage protection is unreliable, Will burn out the thyristor. After the water-cooled cable is disconnected, the medium frequency power supply cannot start to work. If you restart repeatedly without finding out the cause, the medium frequency voltage transformer is likely to be burned out.
When checking the fault, use an oscilloscope to clamp the oscilloscope probe at both ends of the load and observe whether there is an attenuation waveform when the start button is pressed. When confirming that the cable is broken, first disconnect the water-cooled cable from the output copper bar of the electric heating capacitor, and measure the resistance value of the cable with a multimeter (200Ω block). The resistance value is zero when it is normal, and it is infinite when it is disconnected. When measuring with a multimeter, the furnace body should be turned to the dumping position to make the water-cooled cable fall off, so that the broken part can be completely separated, so as to correctly judge whether the core is broken.