The device and the principle of operation of the welding

For successful acquisition of inverter products, it is necessary to know the welding inverter device and the principles of its operation, so that in case of a breakdown it can be repaired, because today devices for inverter type are in high demand and affordable. You can buy them in the store or make yourself.

Scheme of the welding inverter device

Scheme of the device welding inverter.

The principle of operation of the welding inverter

The welding inverter itself is a kind of power supply with high power. The principle of its operation is similar to pulsed power supplies. The similarity lies in the peculiarities of the transformation of energy, namely in the following steps.

The steps of energy conversion in the apparatus for welding:

  • 220 volt AC rectification;
  • DC to high-frequency AC conversion;
  • reduction of high frequency voltage;
  • undercurrent output rectification.

Previously, the basis of the welding device was a high-power power transformer. By reducing the alternating current of the network, he made it possible to obtain the high currents required for welding due to the secondary winding. Transformers operating at a normal frequency of 50 Hz AC mains are very voluminous and weigh a lot.

Inverter internal layout

Scheme of the internal device of the inverter.

Therefore, to get rid of this drawback, a welding inverter was invented. Its size was reduced by increasing the frequency for its operation to 80 kHz or more. The greater the operating frequency, the smaller the dimensions of the device. Mass, respectively, is also less. And this is a saving on materials for its production.

Where to get these frequencies at 50 Hz on the network? For these purposes, an inverter circuit was invented, which consists of high-power transistors that are switched with a frequency of 60 to 80 kHz. But in order for them to function, they need to supply direct current. It can be obtained using a rectifier consisting of a diode bridge, as well as filters for smoothing. The end result is a constant current of 220 volts. Inverter transistors are connected to a voltage-reducing transformer.

Since the switching of transistors occurs at high frequency, the transformer operates on the same. To operate at high frequency currents, less volume transformers are needed. It turns out that the size of the inverter is small, and the working power is not less than that of its cumbersome predecessor operating at 50 Hz.

Due to the need to transform the device, a number of additional details appeared for its uninterrupted operation. Let's get to know them better.

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Features of the device welding inverter

Welding inverter functionality

The functionality of the welding inverter.

To reduce the size and weight, welding devices are assembled using an inverter circuit.

Basic assembly scheme:

  • low frequency rectifier;
  • inverter;
  • transformer;
  • high frequency rectifier;
  • working shunt;
  • electronic control unit.

Each inverter model has its own characteristics, but they are all based on the use of high-frequency pulse converters. As it was written earlier, the alternating current 220V with the help of a powerful diode bridge is straightened and smoothed by capacitors.

On capacitors for filtering the current will be 1.41 times greater than at the output of the diodes for rectification. That is, at a voltage of 220 volts on a diode bridge on capacitors, we get 310 volts of direct current. In the network current can vary, therefore, the capacitors are designed for the working area with a margin (400 volts). Diodes D161 or B200 are commonly used. The GBPC3508 diode assembly operates at a 35 A direct current. A high voltage passes through the diodes and they heat up. Therefore, they are installed on the radiator for cooling. As a protection element, a temperature fuse is attached to the radiator. It opens if the temperature rises to + 90 ° C.

Capacitors set different volume, depending on the modification of the device. Their capacity can reach a size of 680 microfarads.

Direct current from the rectifier and filter is fed to the inverter. It is assembled according to the "slanting bridge" scheme and consists of two high-power key transistors. In the welding apparatus, the main transistors can be IGBT or high-voltage MOSFET. These components are mounted on the radiator to remove excess heat.

In the welding machine must also be high-quality high-frequency transformer, which is a source for lowering the voltage. In the inverter, it weighs several times less than the power transformer in the welding machine. The primary winding consists of 100 turns sews with a thickness of 0.3 mm. Secondary windings: 15 turns of copper wire 1 mm, 2 windings of 20 turns each with a cross section of 0.35 mm. The windings of the primary and secondary windings must match. All windings should be insulated with a varnished cloth or PTFE tape to improve conductivity. Outputs of all windings at the place of fastening protect and solder.

In addition to the main components of the inverter, there is also an anti-sticking mode of the electrode, a smooth adjustment of the welding current, and a protective system against overloads.

The specialist can easily set the required welding current and adjust it during welding. The current range is quite wide - 30-200 A.

The scheme of the welding inverter

The scheme of the welding inverter.

The output rectifier consists of powerful double diodes and one common cathode. Their feature is high speed action. Since their task is to rectify high-frequency alternating current, simple diodes cannot cope with this. Their speed of closing and opening is too low, and this would entail overheating and rapid breakdown. When the output diodes break, they need to be changed to high-speed ones. They, as well as usual, are mounted on a radiator.

During the turn-on of the welding inverter, the electrolytic capacitors are charged. The strength of this current is very large at first and can provoke overheating and breakdown of the rectifier diodes. To avoid this, a “soft start” scheme is used. Its main component is an 8-watt resistor. Just it is the current limiter during start-up of the device.

After the end of the charges of the capacitors and the start of normal operation of the device, the contacts of the electromagnetic field are closed. Next, the resistor does not participate in the work, the current runs through the relay.

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Advantages and disadvantages of welding inverters

The advantages of the equipment in question:

Classification of welding inverters

Classification of welding inverters.

  • high performance;
  • high-quality seam;
  • small dimensions and weight in comparison with the power transformer;
  • with voltage drops in the network, the inverter will have constant quality performance indicators;
  • high efficiency (about 90%);
  • low sparks during welding;
  • the process runs smoothly;
  • minimum losses during production.

This welding equipment has disadvantages. It costs more than a transformer. Inverter is afraid of dust. Therefore, it is necessary to disassemble and clean it from dust 2 times a year. If it is used often (during construction, at work), then cleaning should be carried out more often. Not all devices can be operated at air temperatures below -15 ° C. It all depends on the components that are installed by the manufacturer.

A welding inverter consists of a series of chains that control, regulate its operation and protect against external factors.

All this is necessary for its smooth operation.

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