Rolling Mill Production Line: The Common Failure of Electric Induction Furnace

Tuesday, May 18, 2021

The Common Failure of Electric Induction Furnace

The common failure of electric induction furnace equipment during operation are as follows:

1. The Electric Induction Furnace System Does Not Respond at Startup

① The rectifier board is faulty;

② Over-current and over-voltage protection actions;

③ The main switch is not closed properly;

④ The control power potentiometer is damaged or disconnected;

⑤ The rectifier control power supply is broken.

2. Only the Direct Current Voltmeter Has Instructions, Others Have No Response

① The inverter board and inverter circuit are faulty;

② The inverter power supply fails. There is no 220V power supply for the inverter pulse.

Note: When the power phase voltage of the induction furnace is higher than 240V, it is easy to damage the control power transformer.

3. The Electric Induction furnace Cannot Be Started Successfully When Starting, and the DC Current Is Large, and DC Voltage Is Low (Tens of Volts)

① There is a direct short circuit phenomenon in the inverter part (such as a short circuit between copper bars, breakdown of the electric heating capacitor, etc.)

②There is a problem with the inverter control circuit and the signal-taking part (open circuit or short circuit)

③ There are multiple damages to the inverter thyristor (measured with multimeter R×1 file).

4. There Is Occasional Frequency Sound When Starting the Electric Induction furnace, But Each Instrument is swinging, Or Each Instrument Swings After Starting After the Pin Increases the Power, Overcurrent Or Overvoltage

① Defective inverter control board.

② Improper adjustment of the minimum TF working angle.

③ The water cable is broken or the cable screw is loose.

④ The induction melting furnace is short-circuited or grounded, and the pressed circuit may be a short-circuit on the output side.

⑤The thyristor is defective.

5. When the Main Circuit Is Closed, It Will Trip at the Beginning of the Air, or Over-current Protection. Even If It Is Normal by Chance, There Will Be Abnormal Sound.

① Generally, a certain rectifier thyristor is broken down.

②The performance of the thyristor decreases, or it loses its blocking ability in a certain direction and becomes a diode.

③ There is a short circuit in the rectifier circuit.

6. The Electric Induction Furnace Can Be Started, But the Sound of the Reactor Is Dull. The Meter Swings Accidentally and the DC Voltage Rises to 500V

①The main circuit lacks phase (generally, the constant power board will not have DC voltage output when the phase is lacking);

②The control circuit lacks pulse;

③One of the rectifier thyristors cannot be touched or maintained, and the gate is open-circuited or short-circuited.

7. The Electric Induction Furnace can start, but the ratio of the intermediate frequency voltage to the DC voltage Is large, the voltage Is low, and the DC current Is large

① The breakdown of a bridge wall of the inverter thyristor;

② A certain thyristor does not work (when judging, you can directly use the multimeter to measure the tube voltage drop when working at low voltage. If there is no voltage, it may break down, and pay attention to whether the adjacent bridge wall does not work. For a single-tube bridge wall, if the positive and negative voltages are the same, the related circuit can be checked. There are two cases for the double-two thyristor series circuit. The same as the single-tube circuit, there is generally no pulse between the two tubes, and the voltage is positive and negative. It means that the thyristor that bears the forward voltage is not working, check if there is a control pulse, if the polarity is normal, and if the gate is open circuited).

③The inverter control circuit is abnormal.

④The load does not match, or the minimum TF angle is set improperly.

Note: The breakdown of the KK SCR will cause the secondary parallel diode of the inverter pulse transformer to also break down, which will cause the inverter pulse to have no output. Pay attention to check when replacing the new SCR. This item will also cause reverse change the bridge and three walls to work.

8. The DC Voltage of the Intermediate Frequency Furnace Is Unstable, Or A Certain Range Is Unstable, the Meter Swings, and the Reactor Has A Broken Wire Sound

① The trigger pulse is unstable;

② The characteristics of the rectifier thyristor are poor;

③ Poor contact exists in the main circuit;

④ The PI regulator oscillates due to problems;

⑤ The control circuit leads to interference.

9. The Intermediate Frequency Voltage of the Electric Induction Furnace Is Unstable, Eliminating the Unstable DC Voltage

① Defective inverter thyristor;

② The inverter pulse is unstable;

③ The minimum TF angle is set improperly;

④ Poor contact of the corner load circuit or igniting and connecting;

⑤ The PI regulator has problems with oscillation;

⑥ The control circuit interferes.

10. The Power of the Electric Induction furnace Cannot Be Adjusted up (Without Rectifier and Inverter Faults)

①The load is not matched, too light or too heavy (the load circuit can be adjusted);

②For the circuit users of the crimped connection method, the user does not use the crimped method to connect;

③The output wire loss is too large.

11. Normal Start the Induction Melting Furnace, the Voltage Rises to A Certain Level, and the Restart Phenomenon Suddenly Occurs.

① The minimum angle adjustment is too small;

② The circuit board frequency is not adjusted properly.

12. The New Electric Induction Furnace or Cool Induction Furnace Can Start Well and Can Work Normally. When the Intermediate frequency furnace Is Hot or Full of Molten Steel, the Induction Furnace Will Stop and It Will Be Difficult to Start.