Troubleshooting and examples of medium frequency induction heating power supply (Part 1)

Troubleshooting and examples of medium frequency induction heating power supply (Part 1)

(1) Preparation work before maintenance

①Tools required for maintenance include: digital multimeter or pointer multimeter, dual-trace oscilloscope above 20M, 500V shaker, 40W soldering iron, screwdriver, wrench, etc.

②The information required for maintenance includes: electrical drawings, instructions and other technical information related to the equipment.

③ Before repairing, you should first understand the fault phenomenon of the equipment, what happens when the failure occurs, and check the record data of the equipment.

④ Prepare some wearing parts and commonly used components.

⑤ Before maintenance, it is necessary to conduct a comprehensive inspection of the equipment, tighten all connecting wires and terminals, and check for blackening, sparking, short circuits, virtual connections, etc.

(2)Troubleshooting

The initially adjusted power supply or the power supply during operation fails, and the entire machine fails to start, accompanied by certain phenomena, which are explained below.

① Press the IF start button and adjust the power potentiometer. The power supply has no response or only DC voltage but no IF voltage. The reasons may be:

a. The load is open circuit, that is, the sensor is not connected.

b. The inverter pulse power is too small or there is no pulse, and the inverter tube is not triggered.

c. The rectifier circuit fails and there is no rectified output.

After pressing the intermediate frequency start button, the over-current protection operates and the rectifier is pulled into the inverter state. For newly installed power supplies, you should check whether the voltage polarity is correct, whether the polarity of the inverter pulse is correct, and whether the lead angle is too small. For polarity problems that do not exist in the already running power supply, you can analyze it from the following aspects.

a. Use a multimeter to measure whether the thyristor is damaged.

b. Check whether the fast fuse is broken. If so, replace it.

c. Whether the load circuit is short-circuited or the load is too heavy. You can use an oscilloscope to observe the load waveform to make a judgment.

d. Check whether the starting rake angle is too small. Increase the rake angle appropriately.

e. Whether there is interference in the inverter pulse and whether the characteristics of the thyristor have deteriorated.

f. Whether the overcurrent setting value has changed or needs to be re-set.

g. Is the current feedback too large? If the feedback amount is too large, the oscillation will stop.

h. The rectifier circuit is faulty and the DC output is too low.

i. Whether the insulation of the intermediate frequency power supply is reduced.

j. Is the voltage feedback signal disconnected?