How to use SCR thyristor
The thyristor is the heart of the medium frequency furnace medium frequency power supply. The correct use of the thyristor is crucial to the operation of the medium frequency furnace equipment. It is normal to occasionally damage a few thyristors during the use of the medium frequency furnace. If the thyristor is damaged frequently, it is necessary to be vigilant. The working current of the thyristor is several thousand amperes, and the voltage is usually one or two thousand volts. Good medium frequency furnace main control board protection and good water cooling conditions are essential.
Overload characteristics of thyristors:
The damage of the thyristor of the medium frequency furnace is called breakdown. Under normal water cooling conditions, the current overload capacity of the thyristor of the medium frequency furnace can reach more than 110%; there is no voltage overload capacity, that is, silicon is definitely damaged under overvoltage. Considering the surge voltage, when manufacturing equipment, the manufacturers of medium frequency furnaces often select silicon components according to 2-4 times the working voltage. For example, when the rated working voltage of the medium frequency power supply is 1750V, two medium frequency furnace silicon components with a withstand voltage of 2500V are selected to work in series, which is equivalent to a withstand voltage of 5000V.
Correct installation pressure of thyristor for medium frequency furnace:
When the medium frequency furnace equipment leaves the factory, it is usually installed with a hydraulic press. Even with the maximum force of an ordinary wrench, it is not possible to reach this value manually, so when installing the pressure manually, there is no need to worry that the silicon will be crushed; if it is loosened, it will cause poor heat dissipation and burn silicon due to poor contact between the thyristor and the heat dissipation water cavity.
Radiator structure of thyristor for medium frequency furnace:
Water-cooled cavity + multi-copper column support. If the circulating water contains too much calcium and magnesium ions, which is commonly known as water hardness, it will scale inside the water cavity, causing poor heat dissipation; if leaves and other debris enter the water cavity, it will also cause poor water flow.
The factory test temperature of thyristor is 100℃ (junction temperature). Under normal circumstances, the circulating water temperature of the electric cabinet is kept below 45℃ to ensure its normal operation. Handheld infrared thermometers are very useful. A 350℃ thermometer is only a few hundred yuan, which is not too expensive. Use it to measure the temperature of the thyristor and the radiator of the working power supply, so as to find abnormal points in time and deal with faults.
The water cavity table of the medium frequency furnace radiator must match the size of the thyristor component table to prevent pressure deviation and crookedness, which may damage the device. The radiator table must have a high degree of flatness and finish. It is recommended that the roughness of the radiator table is less than or equal to 0.1mm and the flatness is less than or equal to 0.3mm. During installation, the component table and the radiator table should be kept clean, clean, and free of oil and other dirt.
When installing the medium frequency furnace, the silicon component table and the radiator table should be kept completely parallel and concentric. During the installation process, it is required to apply pressure through the center line of the component so that the pressure is evenly distributed over the entire contact area. When the user installs manually, it is recommended to use a torque wrench to alternately and evenly apply force to all fastening nuts, and the pressure must meet the specified requirements.
When reusing the water-cooled radiator of the medium frequency furnace, special attention should be paid to checking whether the table is smooth and flat, whether there is scale and blockage in the water cavity, and whether the table is sunken. If the above situation occurs, it should be replaced.
