Examples of troubleshooting induction furnace

Fault phenomenon: it is difficult to start, the maximum DC voltage can only rise to 400V after starting, and the reactor vibrates heavily and the sound is dull.

Fault analysis and treatment: this kind of fault is the fault of three-phase full control rectifier bridge. The main possible reasons are as follows:

A. open circuit, breakdown, soft breakdown or electrical parameter performance degradation of rectifier thyristor, observe voltage drop waveform of each rectifier thyristor with oscilloscope, find out damaged thyristor and replace it. When the damaged thyristor breaks down, the voltage drop waveform is a straight line; when the voltage rises to a certain value, it is a straight line; when the electrical parameters fall, the voltage rises to a certain value, the waveform changes. If the above phenomenon occurs, the DC current will be cut off, causing the reactor vibration.

B lack of a set of rectifier trigger pulse. Use oscillograph to detect each trigger pulse (it is better to check on thyristor). When the circuit without pulse is checked, use backward method to determine the fault location and replace the damaged components. When this phenomenon occurs, the output wave head of DC voltage will lack a wave head, resulting in the current cut-off, which is the fault phenomenon.

C rectifier thyristor gate open circuit or short circuit. The thyristor cannot be triggered. Generally, the resistance between G and K is 10-30 Ω.

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