1. Q: A 5 ton intermediate frequency furnace always burns KK tube (2500A/3000V), and always burns the same tube. What is going on?

Answer: First check whether the water cooling system of the pipe is smooth and the absorption capacity is intact. Look at the water-cooled radiator has not been replaced, the radiator water path is not smooth or the contact surface is not flat, it is likely to be like this. Is the incoming line voltage 1350V? Is the KK tube 8 or 16? If it is 8, only the pressure is not enough. If it is 16, you should consider whether there is a problem with the stove.

2, Q: A 10 ton intermediate frequency furnace, the incoming line voltage is 1450V, the resistance and absorption of the incoming line is removed (resistance 250KΩ/400W, capacitance 4KV/4 microfarad), and the resistance heat is generated immediately after the wiring is restored. Remove the dust to measure the resistance and capacity, and check the capacitor with a shaker. No problems were found. Connected to the circuit again, the resistor does not smoke, but a capacitor exploded in about two hours. What is the reason and how to solve it?

A: This situation may be that the resistance and the capacitor do not match. You can try the resistance of about 500W50Ω, and the capacitance is about 3KV of 2 microfarads.

3. Q: 250kg medium frequency furnace, low power (100kw) works normally, the power is increased to 150kw, and the inverter tube is burned immediately. The furnace body, water-cooled cable, capacitor, and intermediate frequency control board have been inspected. What are the reasons for the problem?

A: It may be a problem with a pulse transformer or a problem with the turn-off time of the inverter thyristor.

4. Q: 500KW thyristor intermediate frequency power supply, vacuum induction electric furnace under load, used for nearly 6 years, recently the phenomenon of inverter is difficult to start, how to solve?

A: Use the oscilloscope to test whether the inverter output waveform is normal. If there is a problem, check if the capacitance of the frequency change on the IF control board is appropriate. You can change the capacitor. The IF transformer has an index called “Rated Ratio”. Actually, this index imposes a limit on the impedance of the load. It can be calculated whether the actual impedance is lower than the “Rated Ratio” limit. Especially for zero-start power supply (except for scan start), it is very difficult to start with low impedance.

5, Q: Incoming line 1000V, power 2500kw medium frequency furnace, the stove fired 4 KK, after the replacement boot, everything is normal, burn the tube after 20 minutes. Look at the chip, the breakdown point is on the control pole or the control pole, and the pulse transformer has a normal withstand voltage. Suspected to be disturbed at high power. How can I check for interference or what other causes?

A: It may be that the self-contained capacitor group harmonic i voltage or current is amplified, or the harmonic voltage or current and the furnace subsystem have resonance. Measure the power quality and check the parameters of the furnace for simple calculation.