Fault case 4

Fault phenomenon: after the induction furnace is started, when the power rises to a certain value, the intermediate frequency smelting furnace is easy to over-current protection action, sometimes it will burn out the thyristor elements of the intermediate frequency smelting furnace and restart, the phenomenon remains the same.

Fault analysis and treatment are as follows.

A if it is easy to produce over-current under low voltage just after start-up, it is caused by too small leading angle of inverter in induction melting furnace, which makes inverter thyristor unable to turn off reliably.

B. if the water cooling sleeve of inverter thyristor in medium frequency smelting furnace is cut off or the heat dissipation effect is reduced, the water cooling sleeve shall be replaced. Sometimes it is enough to observe the water output and pressure of the water cooling jacket, but often due to water quality problems, a layer of scale is attached to the wall of the water cooling jacket. Because the scale is a material with extremely poor thermal conductivity, although there is enough water flow, its heat dissipation effect is greatly reduced because of the scale isolation. The judgment method is as follows: run the medium frequency smelting furnace for 10 minutes at a power lower than the over-current value, stop the furnace quickly, and then touch the core of the thyristor quickly. If you feel hot, the fault of the medium frequency smelting furnace is caused by this reason.

C. if there is bad contact and broken wire in the connecting wire of the induction furnace, check the connecting wire of the channel and handle it according to the actual situation. When there is poor contact and broken wire in the channel connecting wire of medium frequency smelting furnace, the phenomenon of sparking will occur when the power rises to a certain value, which affects the normal operation of medium frequency smelting furnace and leads to equipment protection action. Sometimes, instantaneous over-voltage will be generated at both ends due to ignition. If the over-voltage protection is too late, the thyristor components of medium frequency smelting furnace will be burnt out. This phenomenon often occurs over-voltage, over-current action at the same time.

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