The fault phenomena of induction furnace can be divided into two categories: completely unable to start and unable to work normally after starting. In case of failure, the whole system shall be comprehensively checked under the condition of power failure:
（1） Power supply: use a multimeter to measure whether there is power behind the main circuit switch (contactor) and control fuse, which will eliminate the possibility of open circuit of these components.
（2） Rectifier: including six thyristors. Measure the resistance of its cathode anode and gate cathode with multimeter resistance block. The thyristors do not need to be removed during measurement. Under normal conditions, the resistance between anode and cathode shall be infinite, and the resistance of gate cathode shall be 10-30.
（3） Inverter: The inverter includes four groups of fast thyristors and four pulse transformers, which can be checked according to the above methods.
（4） Transformer: Each winding of each transformer should be connected. Generally, the primary side resistance is about tens of ohms, and the secondary pole resistance is several ohms. It should be noted that the primary side of the intermediate frequency voltage transformer is in parallel with the load, so its resistance value is zero.
（5） Capacitor: the electric heating capacitor in parallel with the load may be broken down. The capacitors are generally installed on the capacitor frame in groups. The group of the broken capacitor shall be determined first during inspection. Disconnect the connection point between the busbar and the main busbar of each group of capacitors, and measure the resistance between the two busbar of each group of capacitors;
（6） Water cooled cable: The water cooled cable is twisted with copper wire. When measuring with a multimeter, turn the furnace body to the dumping position to make the water-cooled cable fall off, so that the broken part can be completely separated to correctly judge whether the core is broken.
Through the above inspections, most of the fault causes can be found out.
The abnormal operation after startup is generally manifested in the following aspects:
1. Phase loss of rectifier: the fault shows that the sound is abnormal during operation, the maximum output voltage cannot rise to the rated value, and the strange noise of the power cabinet becomes louder. After shutdown, measure the resistance of each gate pole, and replace the thyristor that is not connected or has a very large gate pole resistance.
2. The three bridge arms of the inverter work: the fault shows that the output current is particularly high, which is the same when the furnace is empty, and the power cabinet works with a heavy voice. After starting, turn the power knob to the minimum position, and you will find that the IF output voltage is higher than normal. If the oscilloscope is used to observe the voltage waveforms between the anode and cathode of the four inverter thyristors in turn, if the three bridge arms are working, it can be seen that the waveforms of two adjacent thyristors in the inverter are normal, in addition, only one of the two adjacent thyristors has no waveform, and the other one is a sine wave.
3. Induction coil fault: Common faults of induction coil are as follows:
Water leakage of induction coil: this may cause coil turn to turn ignition, which must be repaired in time before operation.
The molten steel sticks to the induction coil: the steel slag is hot and red, which will cause the copper tube to burn through. It must be cleaned in time.
The most vulnerable position is 1 silicon controlled rectifier 2 capacitor 3 water cable
The short circuit of SCR is the best one to check, but beware of soft breakdown of SCR. Soft breakdown cannot be measured in the circuit. The general phenomenon of soft breakdown of SCR is that the reactor has a sound, which is very heavy; Capacitance is generally short circuited and terminals are broken; Shell drum; The failure rate of water cable is: open circuit, it is easy to ignore when it seems to be broken;
The sound of induction smelting furnace is indispensable in maintenance. Listen to the sound! When the sound of the reactor is heavy, the fault of the rectifier may be large; When the voice screams, the inverter may have a large fault;
Yiphee Electric Furnace Co.,Ltd specializes in producing induction smelting furnace.Tel(WhatsApp):+86-13450756789, firstname.lastname@example.org