Example of induction furnace maintenance

1. If the buffer speed is not ideal during debugging, fine-tuning can be carried out by adjusting W5, and the buffer time will be shortened by adjusting counterclockwise. On the contrary, the buffer time is longer.

2. In light load operation, if the low end of reactor power trembles, it is excessive voltage limiting, the voltage limiting value can be appropriately amplified, or W5 can be adjusted clockwise until the chatter is eliminated.

3. In case of over-voltage and over-current acting at the same time during maintenance, it should be handled carefully. It is not allowed to enlarge the protection value blindly. The following aspects should be checked emphatically:

1) Small angle too small; 2) converter inductor ignition; 3) inverter silicon soft breakdown;

4) 5) poor contact of water cable; 6) ignition of main circuit to ground (including inductor);

7) Poor insulation of inverter trigger circuit (such as primary leakage of pulse transformer and intermediate frequency transformer);

4. In the step-up line, under certain circumstances, when the isolation capacitor resonates with the intermediate frequency transformer, there will be irregular over-voltage and over-current, which can be verified by short circuiting the isolation capacitor temporarily (the leakage reactance must be ensured, otherwise the intermediate frequency transformer will burn out soon). If the verification is true, the resonance phenomenon can be eliminated by changing the series capacitance (or connecting a damping resistor 500 ~ 5K / 5W in parallel to the capacitor).

5. If the over-current phenomenon occurs during the charging of induction melting furnace, the over-current value can be appropriately enlarged (generally, the over-current is 1.2 times of the current limit). Similarly, the over-voltage phenomenon can also be treated according to the principle.

6. The protection action is divided into overload protection and fault protection,

Overload protection refers to the protection action caused by the change of furnace charge, when this kind of protection action, the reactor does not have excessive impact sound;

Fault protection refers to the protection action caused by inverter overturning, phase loss, undervoltage, component breakdown and other abnormal equipment. During fault protection, the impact sound of reactor is very loud. It is not allowed to blindly amplify the over-current voltage value, otherwise the fault will be increased.

7. The phenomenon of burning silicon during the operation of the equipment can be treated as follows:

A: There are several reasons for burning silicon in fixed position

1) If the cooling is not good, it can be judged by testing the operating temperature of the components. The treatment method is to dredge the waterway or replace the water jacket;

2) The first stage insulation breakdown of pulse transformer usually leads to the damage of inverter power amplifier;

3) The corresponding equalizing resistor or resistance capacitance absorption circuit is damaged or in poor contact;

4) The performance of the silicon is poor (it can't be turned on or off normally). This phenomenon is often ignored by the maintenance personnel. A lot of silicon is burned, and it doesn't return to normal until the silicon is also burned and replaced.

B: Irregular burning of silicon is usually the fault of the protection system. It is necessary to check the over-current, over-voltage, main circuit contact and insulation. Of course, the failure of inverter trigger circuit will also cause irregular silicon burning.

8. The induction furnace can not start normally under the following two conditions:

1) Equipment fault inverter breakdown, water cable open circuit, inductor turn to turn short circuit, compensation capacitor breakdown, trigger circuit abnormal and other reasons, for this kind of fault, only repair the damaged part can recover;

2) The mismatching of load impedance and the difficulty of starting under heavy load can be solved by increasing the gap of reactor, reducing the commutation inductance value, connecting the magnetic ring in resonance circuit, connecting the impulse magnetoresistance (20 / 3KW) at the inverter side of reactor, connecting the bypass resistance (20 / 3KW) at both ends of reactor, changing the constant current starting value (adjusting W10 or W5), and increasing the VCO voltage value (5 ~ 7V) at the center frequency The best way is to reduce the compensation capacitance or increase the turns of inductor to adjust the load impedance.

Small angle problem: due to the existence of converter inductor and lead inductor from inverter output to compensation capacitor, under heavy load, the inverter converter time of load impedance increases, and the original small angle will become smaller. At this time, the inverter may overturn when the power is increased to half. Therefore, when the angle is reduced under no load, it is better to increase it a little bit (generally, UA / UD = 1.2-1.3)

Yiphee Electric Furnace Co.,Ltd specializes in producing induction smelting furnace.Tel(WhatsApp):+86-13450756789, yiphee@yiphee.cn