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Common maintenance of medium frequency induction furnace

(1) Power supply: Use a multimeter to check whether there is electricity behind the main circuit switch (contactor) and control fuse. This will rule out the possibility of disconnection of these components.

(2) Rectifier: The rectifier uses a three-phase fully controlled bridge rectifier circuit, which includes six fast fuses, six thyristors, six pulse transformers and a freewheeling diode.

There is a red indicator on the quick-acting fuse. Normally, the indicator is retracted inside the shell. When the quick-acting blows, it will pop up. Some quick-acting indicators are tight. When the quick-acting blows, it will get stuck inside. , So for the sake of reliability, you can use a multimeter to test the fast-blow on/off gear to determine whether it is blown.

The simple way to measure the thyristor is to measure its cathode-anode and gate-cathode resistance with a multimeter electrical barrier (200Ω block), and the thyristor does not need to be removed during the measurement. Under normal circumstances, the anode-cathode resistance should be infinite, and the gate-cathode resistance should be between 10-50Ω. Too large or too small indicates that the gate of this thyristor fails, and it cannot be triggered to conduct.

The secondary side of the pulse transformer is connected to the thyristor, the primary side is connected to the main control board, and the primary resistance is about 50Ω measured with a multimeter. The freewheeling diode is generally not prone to failure. When checking, use a multimeter diode to measure its two ends. In the forward direction, the multimeter shows that the junction voltage drop is about 500mV, and the reverse direction is blocked.

(3) Inverter: The inverter includes four fast thyristors and four pulse transformers, which can be inspected according to the above methods.

(4) Transformer: Each winding of each transformer should be connected. Generally, the resistance of the primary side is about tens of ohms, and the secondary resistance is a few ohms. It should be noted that the primary side of the medium frequency voltage transformer is connected in parallel with the load, so its resistance value is zero.

(5) Capacitors: The electric heating capacitors connected in parallel with the load may be broken down. The capacitors are generally installed in groups on the capacitor rack. The group of the broken capacitors should be determined first during the inspection. Disconnect the connection point between the bus bar of each group of capacitors and the main bus bar, and measure the resistance between the two bus bars of each group of capacitors. Normally, it should be infinite. After confirming the bad group, disconnect the soft copper skin of each electric heating capacitor leading to the bus bar, and check one by one to find the broken capacitor. Each electric heating capacitor is composed of four cores. The shell is one pole, and the other pole is led to the end cover through four insulators. Generally, only one core will be broken down, and the lead on this insulator will be jumped off. The capacitor can continue to be used, and its capacity is 3/4 of the original. Another fault of the capacitor is oil leakage, which generally does not affect the use, but pay attention to fire prevention.

Shandong Huaxin Electric Furnace Co., Ltd. is a professional induction furnace manufacturer from China, specializing in the production of: medium frequency heating furnace, medium frequency melting furnace, medium frequency furnace, one drag two series resonant medium frequency induction furnace. We are dedicated to serve the majority of domestic and foreign users with advanced technology, high quality products and excellent service.induction furnace manufacturers