1. Overvoltage damage:
Overvoltage is one of the main reasons for the damage of the silicon controlled rectifier. The silicon controlled rectifier has almost no time to withstand overvoltage, and overvoltage will be broken down even in a short time of several milliseconds. Therefore, in the practical application of medium frequency electric furnace, RC absorption loops must be connected at both ends of the silicon controlled rectifier to avoid transient overvoltage caused by various irregular interference pulses. If the thyristor is often damaged, please check whether the components of the absorption circuit are burnt or invalid.
2. Overcurrent damage: excessive current increases the chip temperature. When the chip temperature reaches 175 ℃, the chip will fail and cannot be recovered. As long as the working current does not exceed the rated current, it will not be damaged. Because the over-current breakdown principle is caused by temperature rise, and the process of temperature rise takes a certain time, over-current in a short period of time (hundreds of milliseconds to a few seconds) generally will not be broken down.
3. Overheating damage: it is caused when the working current does not exceed the rated current, mainly because the temperature of the silicon controlled rectifier chip is too high due to the poor operation of the cooling device. For water cooling operation, check whether the inlet water temperature is too high and the flow is sufficient; For those working in the air cooling mode, check whether the number of revolutions of the fan is normal and the ambient temperature cannot be too high. However, whether it is air-cooled or water-cooled, pay attention to the good contact between the chip and the radiator during installation, the flat contact surface, and the sufficient and uniform pressure. Especially for water-cooled silicon controlled rectifier, the tension of the bolts must be uniform, and the scale must be checked and cleaned frequently, Too much scale will also affect the heat dissipation effect and cause overheating damage. If you replace the chip too many times, the contact surface of the radiator will be deformed, which will affect the heat dissipation effect. If a thyristor on your machine is often damaged and no other reason can be found, you should consider replacing the thyristor together with the radiator.
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