„STRUNA”JSC produces wide range of welding equipment in wide sphere of application. In the product range of the company you can find any equipment for gas-shielded welding and welding with coated electrodes, air plasma cutting equipment as well as all the needed consumables. We produce conventional (diode) semi-automatic welding machines and wide range of transistor high-frequency equipment (CHOPPER technology).

STRUNAJSC gain his share of the market thanks to the high quality of produced equipment and strict observation of its guarantee obligations. The main principle in designing our equipment is the long-life of the equipment as well as excellent welding characteristics. Equipment that we produce is unpretentious in use and not so depending on fluctuations of the supply. 100% control of technical and technological parameters enables high reliability. 



Іnvertors or Choppers ?


Struna AD produces and constantly increases the portion of convertible chopper welding machines, why?


With the accumulated experience in utilization of welding inverters their weak part begun to appear. The main disadvantage of the inverter welding source is their reliability and low maintainability which at the same time is extremely expensive.

One of the reasons for the low reliability of the convertors are:

- Many stages of the transformations – electricity power frequency 50Hz stands, filtrates and then converts into high current /50 – 100KHz/ frequency and enters in high frequency transformer. Then the current once again is rectified from high frequency transformer, again filtrated and involve in the welding circuit.

Each unit and single element in this long chain has an end value of constructive reliability and therefore the total reliability of the inventor welding source is much lower than comparable technical parameters decisions.

- After filtration the straight line voltage is 310 V for single phase and 535 V for three-phase inverters. Thus the increased risk when working in dusty conditions, high humidity and low temperatures, /higher probability of electrical break the isolation of electrical circuits and electrical installation in a source/, and also a big risk for the welder.

In addition, the defect occurring at the beginning of the circuit /most common key transistors/, usually spread further on as the primary winding of high frequency transformer in most cases is destroyed. This implies the occurrence of the same 310 or 535 V in the welding circuit. This aspect is deliberately suppressed by advertising.

-        Long series circuit assumes under the influence of the forward and reverse links, weak sustainability. So inverters feel uncomfortable when working in unstable supply network, such as Bulgarian, also under operating from a generator.

Revealed problems are dramatically reduced if management power source on the primary side is avoided, and the inversion is carried out in the welding /low voltage/ circuit. - These are the so-called converters or choppers

In figures are displayed block diagrams of an inverter and a classic CHOPPER.

These problems dramatically reduced if you avoid management power source on the primary side, and the inversion is carried out in the welding /low voltage/ circuit. - These are the so-called converters or choppers.

In the figures are shown a block diagram of a classic  inverter and a CHOPPER.



The specifications for the two approaches are approximately equal with a slight excess of choppers. But the difference in reliability is so great that the leading firms maintain or increase the nomenclature of the chopper power sources for heavy duty application / heavy duty /.


For over fifteen years STRUNA has been working on the technology of self-absorption of high-frequency transistor CHOPPER. No Chinese modules are borrowed or used.

As a result there are 29 types of power sources for MMA, TIG and MIG/MAG welding for different operating conditions and currents from 150 to 630 A, whose main advantages are :

Reliability. Due to lack of power contactors, switches, even that of traditional diode tap power sources – Superior.

Insensitivity within wide extents of the supply voltage. With opportunity to work by a generator or siting conditions.

Wide scope of unification. For example, the entire range from 250 to 630 A is built from one to four power transistor units / A 320 / 60% /. The same applies to interchangeable control units.

The principal chopper circuitand unified nodes in the articles of String giving customers affordable opportunity for a deep modernization of existing obsolete equipment. The result is - welding machines of the latest generation with high economic efficiency.

Alleviate arc ignition. This is particularly important when dealing with corroded or primed base metal. Welding aluminum is also crucial. Due to the fact that CHOPPER - technology essentially is spontaneous. Welding voltage is a series of pulses at constant frequency /27 KHz / and variable duty cycle, but with a constant and relatively high amplitude /45 to 70 V/. This helps to promptly initiate the arc and reduces welding metal drops.

Wire feederSTRUNA, having two patents is capable of working with aluminum or tubular electrode wire and working with steel or CrNi wire, they only confirm that even workers with not so high qualifications can exploit them.

As an optionSTRUNA offers proved in practice apparatus with safety /12 V/ voltage at idle to work in shut areas and with high humidity.