The medium frequency induction heating power supply can start normally and smoothly, but when the power rises to a certain value, what happens when overvoltage or overcurrent protection occurs?

Today, a customer asked us that his medium frequency induction heating power supply can start normally and smoothly, but when the power rises to a certain value, overvoltage or overcurrent protection occurs. What is going on and how to solve it. I believe this problem is not only encountered by this customer, but also by many people. Today, we will talk about what is going on.

(1) Analysis and processing 1

1) First run the medium frequency induction heating power supply with no load and observe whether the voltage can rise to the rated value. If the voltage cannot rise to the rated value and there are multiple overcurrent protections near a certain voltage value, this may be due to the compensation capacitor or thyristor. It is caused by insufficient withstand voltage, but it does not rule out that some part of the circuit is damaged.

2) The fault phenomena of DC smoothing reactor are unstable operation of the equipment, fluctuation of electrical parameters, abnormal sound of the equipment, frequent overcurrent protection and burning of fast thyristors.

(2) Analysis and processing 2

1) In the maintenance of medium frequency induction heating power supply, the fault of DC smoothing reactor is a fault that is difficult to judge and deal with. The common faults of DC smoothing reactors are that the user adjusts the air gap and the number of coil turns of the reactor at will, which changes the inductance of the reactor, affects the filtering function of the reactor, and causes the output DC current to be intermittent, resulting in The inverter bridge works unstable, the inverter fails, and the inverter thyristor is burned out; if the air gap of the reactor is reduced and the number of coil turns is reduced, when the inverter bridge is connected, the reactor's ability to block the rise in current will be reduced in a short period of time and the reactor will be burned out. 

2) Randomly changing the inductance of the reactor will also affect the starting performance of the equipment.

3) If the coil of the reactor is loose, the electromagnetic force will cause the coil to shake when the equipment is working. When the coil shakes, the inductance will mutate, which may easily cause inverter failure during light load startup and low current operation.

4) The insulation of the reactor coil is not good. Short circuit to ground or inter-turn short circuit and spark discharge will cause the inductance of the reactor to jump suddenly and strong electromagnetic interference, making the equipment work unstable and producing abnormal sounds. Frequent overcurrent will burn the thyristor.

After reading the above explanation, you don’t have to worry if you encounter this problem again. However, in order to reduce the failure rate of equipment, we should frequently check and maintain the equipment when using it.