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What are the maintenance techniques for IF induction heating equipment

What are the maintenance techniques for IF induction heating equipment?
 Medium frequency induction heating equipment has a wide range of applications in the fields of heat penetration, melting, quenching, welding, etc. However, because the output power of the equipment is relatively large, electronic components are relatively easy to cause system failure due to excessive temperature. So what are the maintenance techniques for medium frequency induction heating equipment?

First, the system routine inspection

 (1) Power supply: Use a multimeter to measure whether there is power behind the main circuit switch (AC contactor) and the control fuse. This will eliminate the possibility of disconnection of these components.
(2) Rectifier: The rectifier uses a three-phase full-control bridge rectifier circuit, which involves six fast-acting fuses, six thyristors, six pulse transformers and one free-wheeling diode. There is a red indicator on the fast fuse. When the indicator is normal, it will shrink inside the case. When the fuse is blown, it will pop up. Some fast-melting indicators are too tight. When the fast-blow is blown, it will get stuck. Inside, so for safety reasons, you can use a multimeter to test the fast-melting to determine if it is blown.
(3) Inverter: The inverter consists of four fast thyristors and four pulse transformers, which can be routinely checked in the above manner.
(4) Transformer: Each winding of each transformer should be open. Generally, the primary side resistance is about tens of ohms and the second pole is a few ohms. It should be noted that the primary side of the IF voltage transformer is connected in parallel with the load, so its resistance is zero.
(5) Capacitor: The electrothermal capacitor connected in parallel with the load is likely to be broken down. The capacitors are generally grouped and mounted on the capacitor holder. The routine inspection should first determine the group in which the capacitor is broken. Disconnect the connection point between the busbar of each group of capacitors and the main busbar, and measure the resistance between the two busbars of each group of capacitors. Normally, it should be infinite. After confirming the bad group, disconnect the soft copper from each electric capacitor to the busbar, and find the breakdown capacitors by routine inspection. Each electric heating capacitor is composed of four cores, the casing is one pole, and the other pole is respectively led to the end cover through four insulators. Generally, only one core is broken down, and the leads on the insulator are jumped off. This capacitor can continue to be used, and its capacity is 3/4 of the original. Another system failure of the capacitor is oil leakage, which generally does not affect the use, but pay special attention to fire safety. The angle of the capacitor is insulated from the capacitor holder. If the insulation breakdown will ground the main circuit, the resistance between the capacitor casing lead and the capacitor holder can be measured to determine the insulation condition of this part.

Second, the maintenance of abnormal work after startup
Through the above checks, it is usually possible to solve common faults that cannot be started at all. It works abnormally after startup, usually in the following aspects:
(1) Rectifier phase loss: common faults are abnormal sound when working, the maximum output working voltage rises below the rated value, and the power cabinet blame becomes louder. At this time, the output working voltage can be lowered at 200V, and the rectifier can be observed with an oscilloscope. The output working voltage waveform (the oscilloscope should be placed in the power supply synchronization). When the input voltage waveform is normal, there are six waveforms per cycle, and two phases are missing in the absence of phase. This common fault is usually caused by a thyristor of the rectifier that does not have a trigger pulse or a non-conduction. In this case, first look at the gate pulse of the six rectifier thyristors with an oscilloscope, and if so, use a multimeter 200Ω file after shutdown. Measure each gate resistance and replace the thyristor that is unreachable or has a particularly large gate resistance.
(2) Common faults of electromagnetic induction coil: The electromagnetic induction coil is the load of the intermediate frequency power supply. It is made of square copper tube with a wall thickness of 3 to 5 mm. Its common faults are as follows: a. The electromagnetic induction coil leaks, which will cause the coil to ignite between the turns, and must be repaired immediately before use. b. The molten steel sticks to the electromagnetic induction coil, and the steel slag is hot and red, which will cause the copper tube to burn through, and must be completely removed immediately. c. Electromagnetic induction coil short circuit between turns, such common faults are particularly prone to occur in small medium frequency induction furnaces. Because the furnace is small, it is deformed by thermal stress during operation, causing short circuit between turns, and common faults are characterized by large operating current. The working frequency is higher than usual.
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