The principle of operation of the welding inverter: device and characteristics
To choose the right equipment for welding, it is necessary to know the design device and the principle of operation of the welding inverter. If you understand such issues well, can not only be used effectively, but also to repair inverter devices independently.
Inverter welding machines made in Italy
Many inverter models are available on the market today, which allows craftsmen to choose equipment according to their needs and financial capabilities. If you want to save, you can make an inverter welding machine with your own hands.
How the inverter welding machine works
The principle of operation of the inverter device is largely similar to the operation of a switching power supply. And in the inverter, and the switching power supply energy is transformed in a similar way.
The process of converting electrical energy in an inverter type welding machine can be described as follows.
- Alternating current with voltage 220 Volt, flowing in a normal electrical network, will become permanent.
- The received direct current by means of the special block of the electric circuit of the inverter is again turned into alternating current, but has a very high frequency.
- The voltage of high-frequency alternating current decreases, which significantly increases its strength.
- Generated electric current, having a high frequency, significant power and low voltage, becomes permanent, on which welding is performed.
The principle of operation of the welding inverter
The main type of welding machines, previously used, were transformer devices, that increased the welding current by reducing the voltage value. The most serious shortcomings of such equipment, which is actively used today, there is a low efficiency (as they consume a large amount of electricity consumed to heat iron), large size and weight.
Invention of inverters, in which the strength of the welding current is regulated by a completely different principle, allowed to significantly reduce the size of welding machines, as well as reduce their weight. It is possible to effectively regulate the welding current in such devices due to its high frequency. The higher the frequency of the current, which forms the inverter, the smaller the dimensions of the equipment may be.
One of the main tasks, which decides any inverter, Is an increase in the frequency of the standard electric current. This is probably due to the use of transistors, which switch with frequency 60-80 Hz. However, as you know, only direct current can be applied to the transistors, while in a normal electrical network it is variable and has a frequency 50 Hz. To convert alternating current to direct current, in inverter devices install a rectifier, assembled on the basis of a diode bridge.
After the transistor unit, in which alternating current with high frequency is formed, a transformer is located in the welding inverters, which reduces voltage and, in accordance, increases the current. To regulate voltage and current, having a high frequency, smaller dimensional transformers are required (at the same time on the power they do not concede to bigger analogs).
Welding inverter without protective cover
Elements of the electrical circuit of inverter devices
The device of the welding inverter consists of the following basic elements:
- AC rectifier, coming from the ordinary electrical network;
- inverter unit, assembled on the basis of high-frequency transistors (such a unit is a generator of high-frequency pulses);
- transformer, which reduces high frequency voltage and increases high frequency current;
- rectifier of alternating high-frequency current;
- working shunt;
- electronic unit, which is responsible for inverter control.
Whatever the characteristics of a particular model of inverter device, the principle of its operation, based on the use of high-frequency pulse converter, remains unchanged.
An example of the schematic diagram of the inverter (click to enlarge)
Rectifier and inverter units of the equipment in the course of the work strongly heat up, therefore they are installed on radiators, actively dissipate heat. in addition, a special temperature sensor is used to protect the rectifier unit from overheating, which shuts off its power supply when it reaches the temperature 90 degrees.
Inverter unit, which is, essentially, high-frequency high-frequency pulse generator, going on the basis of transistors, oblique bridge. High frequency electrical pulses, formed in such a generator, coming to the transformer, necessary for that, to reduce the value of their voltage.
The most common transformers, used to equip welding inverters, there are devices with the following characteristics: primary winding - 100 turns of wire of the PEV brand (thickness 0,3 mm); 1-i secondary winding - 15 turns of copper wire with a diameter 1 mm; 2-and the 3rd secondary windings - 20 turns of copper wire with a diameter 0,35 mm. All windings are carefully insulated from each other, and the places of their exit are protected and sealed.
Internal device of the welding inverter
Current is supplied to the output rectifier of the welding inverter, having a high frequency. Simple diodes cannot cope with the conversion of such current into DC. That is why the basis of the rectifier are powerful diodes, having a high speed of opening and closing. To prevent the diode unit from overheating, it is placed on a special radiator.
A high power resistor is a must for any welding inverter, which gives the device a soft start. The need to use such a resistor is explained by the fact, that when you turn on the power to the equipment is a powerful electrical impulse, which can cause failure of the diodes of the rectifier unit. That this did not happen, current is fed through a resistor to the electrolytic capacitors, which begin to charge. When the capacitors reach full charge and the transition of the device to normal operation, the contacts of the electromagnetic relay are closed and the current begins to flow to the diodes of the rectifier, already bypassing the resistor.
Output chokes on the welding inverter board
Inverters due to their technical characteristics allow you to adjust the welding current in a wide range - from 30 to 200 A.
The work of all elements of such a welding machine, which differs in compact dimensions, light weight and high power, controls a special PWM controller. Electrical signals are sent to the controller from the operational amplifier, powered by the output current of the inverter. Based on the characteristics of these signals, the controller generates corrective output signals, which can be supplied to the rectifier diodes and transistors of the inverter unit - generator of high-frequency electrical pulses.
In addition to the main, modern welding inverters have a whole list of useful additional options. To such characteristics, which greatly facilitate the work with the device and allow you to get quality, reliable and beautiful welded joints, should include forcing the welding arc (rapid heat), anti-stick electrode, smooth regulation of welding current, the presence of a system of protection against overloads.
Circuit board with the main elements of the inverter
The feasibility of using inverters and their main disadvantages
The widespread use of welding inverters is due to a number of significant advantages, which they own.
- Devices of this type are characterized by high power and performance.
- Welded seam, formed using inverters, characterized by high quality and reliability.
- Along with high power, devices of this type differ in the compact sizes and small weight, which makes it easy to move them to that place, where welding work will be performed.
- Welding inverters have high efficiency (close 90%), the consumed electric energy is used in them more efficiently, than in transformers.
- Due to the high efficiency of such devices are characterized by economical consumption of electricity consumed.
- In the process of performing welding work with the help of an inverter, the molten metal is sprayed slightly, which affects the more rational consumption of consumables.
- Inverters provide the ability to smoothly adjust the welding current.
- Due to the presence of additional options in such devices, the level of qualification of the welder has almost no effect on the quality of work.
- The wide versatility of inverters eliminates the question, which device to choose for welding by different technologies.
Inverter devices are chosen in this case, when you need a device, characteristics of which provide high stability of combustion of a welding arc in any situation. When using inverters there is no question about that, which electrode to choose for welding, as by means of this equipment it is possible to cook metal by electrodes of any type.
Of course, Inverters also have disadvantages, but not many. This should include a fairly high cost of such devices, in comparison with usual welding transformers. Expensive such devices are under repair, which is most often associated with the need to replace high-power transistors (their cost can be up to 60% the cost of the whole device).
Inverters are very sensitive to negative external factors - dust, dirt, precipitation and frost. If you need an inverter for field work, will have to build a closed and heated area for it.
