What are the reasons for the medium frequency electric furnace to burn the thyristor?
The medium frequency electric furnace is an electromagnetic induction heating device. According to the basic principle of electromagnetic induction, the three-phase power frequency alternating current is rectified into direct current, and then the direct current is converted into an adjustable medium frequency current, which supplies a load composed of a capacitor and an induction coil (coil and Capacitors can be connected in parallel or in series), generate high-density magnetic lines of force in the induction coil, and cut the metal material contained in the induction coil, which produces a large eddy current in the metal material. This eddy current also has some properties of medium frequency current, that is, the free electrons of the metal itself flow in the resistive metal body to generate heat. According to this principle, heat the metal.
The most important variable frequency power supply for medium frequency electric furnaces is the thyristor, which is what we usually call thyristor or silicon. It has the characteristics of small size, strong function, and relatively simple structure. It is a very commonly used semiconductor device. If the medium frequency electric furnace is always burning out the transistor under normal use, we must be vigilant, analyze the cause, and solve the problem
First, we must comprehensively inspect the medium frequency electric furnace
1. Focus on checking whether the insulation layer of the induction coil of the medium frequency electric furnace is damaged, and whether the insulation between the induction coil and the yoke is intact
2. Whether the water-cooling cable of the medium frequency electric furnace is bulged, and whether the connector is loose
3. Whether there is leakage or blockage in the cooling water pipe of the medium frequency electric furnace body
4. Is the grounding protection of the medium frequency electric furnace intact?
5. After confirming that the inspection points are in good condition, switch the furnace body of the medium frequency electric furnace and send electricity to the test furnace
It is necessary to check whether the connecting bolts of the medium frequency electric furnace are connected to the copper bar, the furnace switch, the reactor, the capacitor, etc. are loose, whether there is other metal overlap, whether there is water leakage, whether the cooling is intact, whether the reactor core is displaced, Whether the capacitor has bulging and leakage.
It is necessary to check whether the cooling water jacket of the medium frequency electric furnace turns tube is cooled properly, whether the contact surface with the turns tube is flat, and whether the installation meets the requirements.
To check the quality of the medium frequency electric furnace thyristor, whether the thyristor is broken down immediately after starting or the thyristor is broken down when the load increases, check whether the electrical parameters of the thyristor meet the requirements.