1, induction heating furnace inverter thyristor water cooling jacket internal water cut or heat dissipation effect decreased
Replace the water jacket. Sometimes it is sufficient to observe the water output and pressure of the water jacket, but often due to water quality problems, a layer of scale is attached to the wall of the water jacket. Since the scale is an object with poor thermal conductivity, although there is enough water flow, However, because the scale is isolated, its heat dissipation effect is greatly reduced. The method of judging is: running the power at a power lower than the overcurrent value for about ten minutes, stopping quickly, and quickly touching the core of the thyristor element by hand after stopping, if the hand feels hot, the fault is caused by Caused by this.
2, the channel connection wire has poor contact and disconnection
Check the tank connection wires and dispose of them as appropriate. When the connecting line of the tank circuit has poor contact or disconnection, the fire will rise after a certain value rises, which will affect the normal operation of the induction heating furnace, resulting in the protection of the induction heating furnace. Sometimes a transient overvoltage will occur across the thyristor due to a fire. If the overvoltage protection action is too late, the thyristor component will burn out. This phenomenon often occurs when overvoltage and overcurrent occur simultaneously.
3, the load is reduced to ground insulation
The insulation of the load circuit is reduced, causing the load to ignite between the ground, disturbing the triggering time of the pulse or forming a high voltage across the thyristor, and burning the thyristor component.
4. When the power supply is in anti-correlation, the instantaneous glitch voltage withstand reverse voltage is too high.
In the main circuit of the intermediate frequency power supply, the instantaneous reverse glitch voltage is absorbed by the RC absorption. If the resistor or capacitor is open in the snubber circuit, the instantaneous reverse glitch voltage will be too high to burn out the thyristor. In the case of power failure, use a multimeter to measure the resistance of the absorption resistor and the capacity of the absorption capacitor to determine whether the resistance absorption circuit is faulty.
5, pulse trigger loop failure
If the trigger pulse is suddenly lost during the operation of the induction heating furnace, the inverter will be opened, and the output of the intermediate frequency power supply will generate high voltage, which will burn out the thyristor components. This type of fault is generally caused by inverter pulse formation and output circuit failure. It can be inspected by an oscilloscope. It may also be that the inverter pulse lead is in poor contact. You can shake the wire connector by hand to find the fault location.
6, induction heating furnace load open circuit during operation
When the induction heating furnace is running at high power, if the sudden load is in an open state, a high voltage burnout thyristor element will be formed at the output end.
7, induction heating furnace load short circuit during operation
When the induction heating furnace is running at high power, if the load is suddenly in a short-circuit state, it will have a large short-circuit current impact on the thyristor. If the over-current protection action is not protected in time, the thyristor component will be burned out.
8, protection system failure (protection failure)
Whether the thyristor can be safe is mainly guaranteed by the protection system. If the protection system fails, the induction heating furnace will work a little bit abnormally, which will lead to the safety of the thyristor. Therefore, inspection of the protection system is essential when the thyristor burns out.
9, thyristor cooling system failure
The thyristor generates a large amount of heat during operation and needs to be cooled to ensure normal operation. Generally, there are two ways to cool the thyristor: one is water cooling and the other is air cooling. The application of water cooling is more extensive, and air cooling is generally only used for power induction heating furnaces below 100 KW. Water-cooled medium-frequency induction heating furnaces are usually equipped with water pressure protection circuits, but basically they are all protected by total water. If there is water blockage on a certain road, it cannot be protected.
10, reactor failure
The internal ignition of the reactor causes the current on the inverter side to be interrupted, and a high voltage burnout thyristor is also generated on the inverter input side. In addition, if the reactor is replaced during maintenance, and the inductance and core area of the reactor are less than the required value, the reactor will burn out the thyristor due to the loss of current limit during saturation when the reactor is working at high current.
