Principle and common fault analysis of DC welding machine and its difference from AC welding machine

The DC electric welding machine is a kind of electric welding machine that uses the high voltage arc generated when the positive and negative poles are short circuited instantaneously to melt the solder on the welding electrode, so that they can achieve the purpose of atomic combination. Now, let’s get to know it together with the Speed Plus Mesh!

Principle of DC welding machine:

DC electric welding machine is an electric welding machine whose output power is DC power. It has the advantages of easy arc ignition, stable arc and good welding quality.

DC electric welding machine can also be said to be a high-power rectifier, which is divided into positive and negative poles. When AC power is input, it will be rectified by the rectifier after transformer transformation, and then output a power supply with external characteristics of decline. When the output terminal is connected and disconnected, huge voltage changes will occur. When the two poles are short circuited, the arc will be ignited. The generated arc will be used to melt the welding electrode and welding materials, and then the purpose of combining them will be achieved after cooling. The welding transformer has its own characteristics, and the external characteristic is that the voltage drops sharply after the ignition of the welding rod.. In addition to the primary 220/380 voltage conversion, the secondary coil also has tap conversion voltage, and the adjustable core electric welding machine is generally a high-power transformer.

Common fault analysis of DC welding machine:

1. When starting the electric welding machine, it was found that the AC contactor could not reclose.

There are several reasons for this failure, which may be:

 (1) No input voltage, low line or phase loss,

 (2) It is possible to control the burning out of transformer T2,

 (3) It is also possible that the thermal switch on the secondary side is disconnected, and these reasons may exist.

Troubleshooting and maintenance methods:

 (1) Check the power distribution of power sockets, leakage protection switches and power distribution cabinets to see if it is a problem, find out the causes and eliminate them.

 (2) Check the continuity of the input wire with the resistance of the multimeter, and connect the broken wire or the falling part.

 (3) First, disconnect the power switch, and then detect the resistance between line 233 and line 235. If the fault still exists after 15 minutes of disconnection and waiting, the secondary side thermistor needs to be slid.

2. After the welding machine switch is turned on, the AC contactor CR1 pulls in, but the fan does not turn.

The failure may occur due to:

 (1) There are some faults in fan motor circuit and voltmeter circuit.

 (2) The main contact of AC contactor CR1 cannot be contacted.

For this problem, the specific maintenance methods are as follows:

 (1) First, detect the voltage at the power output terminal. If there is voltage, the circuit of the fan motor may be faulty.

 (2) Check whether there are dust or foreign matters between the main contacts of the contactor. If they exist, they will block and cause all fusions. But generally speaking, it will not happen.

Differences between DC welding machine and AC welding machine:

1. The output current of DC welding machine has no “zero crossing”, so the arc is not easy to break, which makes the arc stable.

2. Because the peak value of the secondary voltage of the transformer is certain, the DC voltage is higher than the AC no-load voltage, so it is easy to start an arc.

3. DC welding machine has more rectifier diodes than AC welding machine, so the cost is relatively high.

4. If the AC welding machine is high-power, it can use two-phase electricity at most, which will cause imbalance of three-phase electricity. However, it is no problem to use three-phase rectifier for high-power DC welding machine.