After sales training for induction melting furnace

Induction melting furnace is a non-standard induction heating equipment in general. It involves the professional knowledge of many disciplines, such as mechanics, electronics, electromagnetics, thermal engineering, materials science, strong and weak electricity, automatic control, PLC, hydraulic knowledge, etc . therefore. There is a certain requirement for the knowledge of the maintenance personnel of the induction melting furnace. During the after-sales maintenance process, it can accurately determine the problem and solve the problem to ensure the normal operation of the induction melting furnace induction equipment.

1 Induction melting furnace‍Preparation work before maintenance

a) Induction melting furnace ‍The tools required for after-sales maintenance include: digital multimeter or pointer multimeter, dual trace oscilloscope with 20M or more, 500V shaker, 25W electric iron, screwdriver, wrench, etc.

b) Induction melting furnace ‍The required materials for after-sales personnel maintenance include: technical information such as relevant electrical diagrams and instructions of the equipment.

c) Induction melting furnaces. After-sales personnel should first understand the failure phenomenon of the equipment, what happens when the failure occurs, and check the record data of the equipment.

d) Always prepare some wearing parts and common components before repairing.

e) Induction melting furnace ‍It is necessary for the after-sales personnel to carry out a comprehensive inspection of the equipment before repairs, fasten all connecting wires and terminals, and see if there are blackening, sparks, short connections, virtual connections, etc.

2 Induction melting furnace

The initial adjustment of the intermediate frequency power supply failed, the induction melting furnace failed to start, and accompanied by certain phenomena, this is explained as follows:

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

a. Induction melting furnace ‍The load is open and the sensor is not connected;

b. The inverter pulse power of the intermediate frequency power supply is too small or no pulse, and the inverter tube is not triggered;

c. The intermediate frequency power supply rectifier circuit is faulty and there is no rectifier output.

B) After pressing the IF start button, the overcurrent protection is activated and the rectifier is pulled into the inverter state.

For the newly installed power supply, check whether the voltage polarity is correct, whether the polarity of the inverter pulse is correct, and whether the leading angle is too small. There is no polarity problem for the running power supply, which can be analyzed from the following aspects:

a. Whether the thyristor is damaged, use a multimeter to measure and judge

b. Whether the fast-melt is damaged, if it is bad, replace it

c. Whether the load circuit is shorted or the load is too heavy

d. Whether the leading angle is too small

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

f. Whether the over current setting value has changed, re-set

g. Whether the current feedback is too large and the feedback amount is too large to stop the oscillation

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

i. Is the IF power supply insulation reduced?

j. Whether the voltage feedback signal is disconnected

3 Troubleshooting examples of induction melting furnaces

1) Symptom: The device cannot be started. Only the DC ammeter has instructions at startup, and there are no instructions for DC voltage and intermediate frequency voltage.

analysis:

a. There is a lack of pulse phenomenon in the inverter trigger pulse;

b. Inverter thyristor breakdown;

c. capacitor breakdown;

d. The load is short-circuited and grounded;

e. The IF signal sampling circuit is open or shorted.

2) Failure phenomenon: Startup is difficult. After starting, the intermediate frequency voltage is more than twice the DC voltage, and the DC current is too large. analysis:

a. A thyristor of the inverter circuit is damaged;

b. One of the inverter thyristors is not conducting.

c. There is an open circuit or polarity error phenomenon in the intermediate frequency signal sampling circuit;

d. Inverter leading angle phase shifting circuit fails;

3) Failure phenomenon: It is difficult to start. After starting, the DC voltage is difficult to reach or reach full load, and the reactor has large vibration and dull sound. analysis:

e. The rectifier thyristor is open circuit, breakdown, soft breakdown or the performance of electrical parameters is degraded.

f. missing a set of rectified pulses,

g. Rectifier thyristor gate is open or shorted,

4) Failure phenomenon: It can start, but it will stop immediately after starting, and the device is in the state of continuous repeated startup. Analysis: h. Lead angle is too small;

i. The load oscillation frequency is at the edge of its excitation frequency;