Maintenance of abnormal response after start-up of medium frequency induction heating equipment
The working principle of medium frequency induction heating equipment is to put a metal cylinder in an induction coil with alternating medium frequency current. The metal cylinder does not directly contact the induction coil. The temperature of the energized coil itself is very low, but the surface of the cylinder is heated to Redness, even melting, and the speed of this redness and melting can be achieved by adjusting the frequency and the strength of the current. Medium frequency induction heating equipment has a wide range of applications in the fields of diathermy, smelting, quenching, welding, etc. However, due to the large power of the equipment, electronic components are prone to malfunction due to overheating. How to deal with abnormal response after startup, here are several situations.
(1) Phase failure of the rectifier: The fault is manifested as abnormal sound during operation, the maximum output voltage rises below the rated value, and the power cabinet will make a strange sound. At this time, the output voltage can be lowered to about 200V, and the rectifier can be observed with an oscilloscope. Output voltage waveform (the oscilloscope should be placed in synchronization with the power supply). Normally, the input voltage waveform has six waveforms per cycle, and two are missing when there is a phase loss. This fault is generally caused by a rectifier thyristor without trigger pulse or triggering non-conduction. At this time, you should use an oscilloscope to look at the gate pulses of the six rectifier thyristors. If any, use a multimeter to measure 200Ω after shutting down. Click each gate resistance and replace the thyristor that is blocked or the gate resistance is particularly large.
(2) Induction coil failure: The induction coil is the load of the medium frequency power supply. It is made of a square copper tube with a wall thickness of 3 to 5 mm. Its common faults are as follows: the induction coil leaks water, which may cause ignition between the coil turns, which must be repaired in time to operate; the molten steel sticks to the induction coil, the steel slag heats up and becomes red, which will cause the copper pipe to burn through. Clear and clean in time; short circuit between turns of the induction coil. This type of fault is particularly easy to occur on small medium frequency induction furnaces. Because the furnace is small, it is deformed by thermal stress during operation, resulting in short circuit between turns. The fault is manifested as a large current and working frequency. Higher than usual.
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