Method of Reducing Silicon Burning Probability in Medium Frequency Furnace

Method of Reducing Silicon Burning Probability in Medium Frequency Furnace

The following describes the method of reducing the probability of silicon burning in the medium frequency furnace.

The thyristor is the heart of the medium frequency power supply of medium frequency furnace, its correct use is very important for the operation of equipment. It is normal to damage several thyristors occasionally during the use of medium frequency furnace. If silicon is often burned, it will cause alarm. The working current of the thyristor is several thousand a and the voltage is usually one or two thousand v. good protection of the main control board and good water-cooling conditions are necessary.

Overload characteristic of thyristor: the damage of thyristor is called breakdown. Under normal water-cooling conditions, the current overload capacity can reach more than 110%; without voltage overload capacity, that is to say, silicon is definitely damaged under overpressure. Considering the surge voltage, manufacturers often choose the silicon element according to 3-4 times the working voltage when manufacturing equipment. For example, when the rated working voltage of the intermediate frequency cabinet is 1750V, two silicon elements with voltage resistance of 2500V are selected to work in series, which is equivalent to 5000v.

Correct installation pressure of SCR: 150-200kg / cm2. When the equipment is delivered from the factory, it is generally installed by the hydraulic press. The maximum force of an ordinary wrench can't reach this value manually, so it's unnecessary to worry that silicon will be crushed during manual pressure mounting; if the pressure is loose, silicon will be burned due to poor heat dissipation.

Radiator structure of silicon controlled rectifier: water cooling cavity + multi copper pillar support. If the circulating water is too hard, it will scale inside the water chamber and cause poor heat dissipation; if the water chamber enters into leaves and other debris, it will also cause poor water flow.

The factory test temperature of the thyristor is 100 ℃ (junction temperature). Generally, the circulating water temperature of the electric cabinet is kept below 45 ℃ to ensure its normal operation. The hand-held infrared thermometer is very useful. The thermometer at 350 ℃ costs only a few hundred yuan, which is not too expensive. It can be used to measure the temperature of thyristor and radiator of the working power supply, find out the abnormal points in time, and deal with the faults.

The surface of the radiator must match the dimension of the surface of the element to prevent the device from being damaged due to the bias and skew of the pressure. The surface of the radiator must be smooth and smooth. It is recommended that the surface roughness of the radiator is less than or equal to 1.6mm, and the flatness is less than or equal to 30mm. During installation, the component table and radiator table shall be kept clean and free of dirt such as oil stain.

During installation, keep the silicon element table and the radiator table completely parallel and concentric. During installation, it is required to apply pressure through the centerline of the element to make the pressure evenly distributed in the whole contact area. When the user installs by hand, it is recommended to use a torque wrench to alternately and evenly force all fastening nuts, and the pressure should meet the specified requirements.

When reusing the water-cooled radiator, special attention shall be paid to check whether the tabletop is smooth and flat, whether there is scale and blockage in the water chamber, especially whether the tabletop has sagged, if any, it shall be replaced.