induction melting furnace IF  power supply three-bridge arm operation and maintenance

Maintenance and discussion of common faults of induction melting furnace power supply

First, the intermediate frequency power supply three bridge arm operation 1

Fault phenomenon: difficulty in starting, noise noise. DC voltage is low, DC current is high, and the intermediate frequency voltage is about 3 times higher than DC voltage. When observing the bridge arm waveform with an oscilloscope, there is a bridge arm in a straight line (no pressure drop). The other bridge arm is a very high sine wave. Reason: 1) The sinusoidal arm thyristor is not conducting.

Second, the intermediate frequency power supply three bridge arm operation 2

Fault phenomenon: difficult to start, occasionally start the middle frequency whistling sound is lower than normal, the DC voltage is low, the DC current is very large, and the DC voltage overcurrent is increased. When the oscilloscope is used to observe the waveform of the inverter bridge arm, one arm is normal and the other arm is straight line.

1. It is possible that the component of the bridge arm on the inverter side is damaged or broken down. (Use a multimeter to check the resistance of the thyristor; check whether the capacitance in the RC absorption circuit breaks down; check if the external line is short-circuited.)

2. It is possible that the thyristor with a bridge arm on the inverter side is not triggered to conduct (check whether the inverter trigger pulse is normal; whether the trigger power of the thyristor is too large)

3. The reverse pressure angle of the inverter is too small, so that the thyristor can not be turned off (increasing the inverter back pressure angle, increasing the reserve time, making the thyristor reliable tube break; or increasing the capacitance of the load circuit to reduce the frequency)

4. Short-circuiting or short-circuiting of the load ring to the ground will cause the three-bridge arm to operate, causing overcurrent.