Example 1 of troubleshooting of induction melting furnace
1. When the intermediate frequency voltage of the induction melting furnace rises to 500V, the DC reactor emits a lower bang, and then the power is increased and the overcurrent protection is activated.
This phenomenon is caused by the performance degradation of the inverter trigger pulse transformer. When the intermediate frequency voltage is high, capacitive leakage is formed, which disturbs the positioning formation of the trigger pulse, causes the inverter to trigger the positioning change, and causes the inverse conversion flow to fail. It is difficult to deal with this fault, and all inverter trigger pulse transformers should be replaced.
2. After the induction melting furnace is empty, the DC reactor emits a continuous chuck sound, and the overcurrent protection is activated when the intermediate frequency voltage rises to about 500v.
1) This kind of fault is caused by oil leakage of the resistance-capacitance protection capacitor of the inverter circuit of the induction melting furnace, which causes too much loss. Because the fault protection capacitor is equivalent to a short circuit under the intermediate frequency voltage during operation, the fault can only be eliminated by replacing the new protection capacitor. , The
2) Poor performance of the bridge arm thyristor of the induction melting furnace causes abnormal commutation, but the reactor noise is louder!
3) There is a breakdown or poor contact inside the intermediate frequency voltage transformer or current signal transformer, which causes unstable inverter operation, and the reactor also has a large abnormal noise.
4) The internal insulation of the inverter pulse transformer of the induction melting furnace is poor, and the same is true. Taking into account the abnormal sound of the reactor in the usual maintenance methods, it is often mistaken as a fault in the rectifier part, but it is not actually the case. Observing the waveform of the DC output terminal of the rectifier bridge with an oscilloscope, it is obvious that there is a short-circuit phenomenon. It is different from the non-conducting waveform of a thyristor in the rectifier bridge. The former has a narrower gap and the latter has a wider gap. In the actual repair, as long as the above waveform is found, it can be definitely caused by the fault of the inverter part.Don't go to the rectifier part to find the problem blindly.
3. The induction melting furnace device of the booster circuit cannot be started, and it can barely be started by changing to a non-boosting circuit, that is, simply paralleling the empty furnace. Before the start is successful, the DC reactor emits a hum, and then it is basically normal. To
This phenomenon is generally caused by the poor performance of the inverter thyristors of the induction melting furnace. Some thyristors are made incorrectly and the marked parameters are inconsistent with the actual ones. The method of inspection is to connect the non-boost circuit first, start the power slowly, and observe the pressure drop of the thyristor with an oscilloscope. The pressure drop of the thyristor in the near-start state is a beating sine wave. Find out where the problem lies and replace the thyristor to work normally. In actual operation, some thyristors turn off for a long time, which will cause failure to start. When a fault occurs, it must be carefully observed and distinguished and resolved.
4. Method of adjusting the power of induction melting furnace
The normal operation of the induction melting furnace can only indicate that the components of the induction melting furnace are intact, and the power of the induction melting furnace cannot be increased, indicating that the adjustment of the parameters of the induction melting furnace is inappropriate. The methods to adjust the power of the induction melting furnace are:
1) The rectifier circuit of the induction melting furnace is not adjusted properly, the DC voltage does not reach the maximum value, the rectifier tube is not fully turned on, and the DC voltage does not reach the rated value, which affects the power output;
2) The medium frequency voltage value of the induction melting furnace is adjusted too high or too low, which will affect the power output;
3) Current limiting and voltage limiting, improper adjustment of the interception voltage value makes the power output low; adjust the current limiting potentiometer of the control panel of the induction melting furnace
4) The mismatch between the furnace body of the induction melting furnace and the intermediate frequency power supply seriously affects the power output;
5) Too many or too few compensation capacitors for induction melting furnaces will not get the best power output of electrical and thermal efficiency, that is, the best economic power output will not be obtained;
6) The distributed inductance of the output circuit of the induction melting furnace and the additional inductance of the resonance circuit are too large, which also affects the maximum power output.
