Weld with direct current. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / welding equipment

 Comments on the article

The advantages of DC welding machines over their "alternating current counterparts" are well known. This includes soft arc ignition, the ability to connect thin-walled parts, less metal spatter, and the absence of non-welding areas. There is not even an annoying (and, as it turned out, harmful to people) cod. And all because there is no main feature inherent in AC welding machines - intermittent arc burning when the sinusoid of the supply voltage flows through zero (Fig. 1).

Rice. 1. Graphs explaining the process of welding on alternating (a) and direct (b) current

Turning from graphs to real designs, it should also be noted: in AC machines, to improve and facilitate welding, powerful transformers are used (the magnetic circuit is made of special electrical iron with a steeply falling characteristic) and a deliberately high voltage in the secondary winding, reaching up to 80 V, although for 25-36 V is enough to support the arc burning and metal deposition in the welding zone. We have to put up with the prohibitively large mass and dimensions of the apparatus, increased power consumption. By reducing the voltage transformed into the secondary circuit to 36 V, it is possible to lighten the weight of the "welder" by 5-6 times, bring its dimensions to the size of a portable TV while improving other performance characteristics.

But how to ignite an arc with a low-voltage winding?

The solution was to introduce a diode bridge with a capacitor into the secondary circuit. As a result, the output voltage of the modernized "welder" was increased by almost 1,5 times. The opinion of experts is confirmed in practice: when the 40-volt DC barrier is exceeded, the arc easily ignites and burns steadily, allowing even thin body metal to be welded.

Rice. 2. Schematic diagram of a DC welding machine

The latter, however, is easily explained. With the introduction of a large capacitance into the circuit, the characteristic of the welding machine also turns out to be steeply falling (Fig. 3). The initial increased voltage created by the capacitor facilitates the ignition of the arc. And when the potential on the welding electrode drops to U2 of the transformer (working point "A"), a process of stable arc burning with metal deposition in the welding zone will occur.

Rice. 3. Volt-ampere characteristic of the "welder"

The "welder" recommended by the author can be assembled even at home, based on an industrial power transformer 220-36 / 42 V (these are usually used in systems for safe lighting and powering low-voltage factory equipment). After making sure that the primary winding, containing, as a rule, 250 turns of insulated wire with a cross section of 1,5 mm2, is intact, the secondary ones are checked. If their condition is not important, everything (with the exception of a working network winding) is deleted without regret. And in the vacated space, a new secondary winding is wound (until the "window" is filled). For the recommended 1,5 kVA transformer, this is 46 turns of a 20 mm2 copper or aluminum bus with good insulation. Moreover, a cable (or several insulated single-core wires twisted into a bundle) with a total cross section of 20 mm2 is quite suitable as a bus.

The choice of electrode cross-section depending on the power of the transformer

The rectifier bridge can be assembled from semiconductor diodes with an operating current of 120-160 A by installing them on heat sinks-radiators 100x100 mm. It is most convenient to place such a bridge in one housing with a transformer and a capacitor, displaying a 16-ampere switch, a peephole of the “On” signal light, as well as “plus” and “minus” terminals on the front textolite panel (Fig. 4). And to connect to the electrode holder and the "ground" use a piece of a single-core cable of the appropriate length with a copper cross section of 20-25 mm2. As for the welding electrodes themselves, their diameter depends on the power of the transformer used.

Rice. 4. Homemade DC welding machine

And further. When testing, it is recommended, by disconnecting the device (10 minutes after welding) from the network, to check the thermal conditions of the transformer, diode bridge and capacitor. Only after making sure that everything is in order, you can continue to work. After all, an overheated "welder" is a source of increased danger!

Of the other requirements, it is worth noting, I think, that the welding machine must be equipped with a spark-protective mask, gloves and a rubber mat. The place where welding work is performed is equipped with fire safety requirements. In addition, it is necessary to ensure that there are no rags or other combustible materials nearby, and the connection of the "welder" to the network must be carried out in compliance with electrical safety rules through a powerful plug connector of the electrical panel at the entrance to the building.

Author: V.Konovalov, Irkutsk

See other articles Section welding equipment.

<< Back

Latest news of science and technology, new electronics:

Wacom Movink OLED drawing tablet 19.04.2024

In the world of digital art, choosing the right tool is key to an artist's creative process. Wacom, known for its innovative solutions in the field of graphics tablets, introduced its new development - Movink, the first drawing tablet with an OLED screen. Let's dive into the details of this device and explore its features. Wacom Movink is not just a tablet, it is a tool that combines advanced technology with aesthetic design. The tablet is a thin device with an OLED screen designed specifically for digital artists. One of the main features of Movink is its ultra-thin body. With a thickness ranging from 4 to 6,6 mm and a weight of only 420 grams, this device fits easily in the hand and is suitable for use in any situation. Comparative analysis shows that it is 66% thinner and 55% lighter than previous Wacom models. The tablet screen has a diagonal of 13,3 inches and Full HD resolution, manufactured by Samsung ... >>

The habit of touching your face is inherent in nature. 18.04.2024

The COVID-19 pandemic has led to a number of changes in daily life, including new ways of looking at habits we take for granted. One such habit that has come under the microscope of researchers is unconscious face touching. Surprisingly, this habit has roots deep in human evolution and general primate biology. We don't always realize how often we touch our face. Despite medical concerns about hygiene and recommendations during the pandemic, this gesture remains part of our everyday behavior. Israeli researchers, trying to understand why we do this so often, turned their attention to aspects of our general biology. Research shows that primates, including humans, spend significant time smelling their hands and also touching their faces. Scientists note that this habit is rooted in evolutionary adaptations associated with communication and social relationships in a community. Smells play an important role in the lives of primates, including humans. ... >>

Mining as a heating system 18.04.2024

Finland, a country with a harsh climate, has always looked for innovative ways to provide heating. In recent years, they have begun using exhaust heat from industrial processes, including Bitcoin mining, to reduce costs and carbon emissions. District heating systems, such as those in Finland, supply multiple buildings with heat from a single source, making them efficient and convenient. However, until recently, the main heat sources for these systems were biomass, coal, natural gas and other types of fuel, often expensive and negatively affecting the environment. Finland faces the challenge of reducing its carbon emissions and fuel costs. The solution was found in using the heat generated by industrial processes, and here Bitcoin mining plays a key role. Local companies have already integrated mining farms with district heating facilities and plan to use high-temperature water from miners to provide systems ... >>

Random news from the Archive Czech hydrogen strategy 07.08.2021 The Czech government approved the Hydrogen Strategy prepared by the Ministry of Industry and Trade and based on four main areas: production of low-carbon hydrogen, low-carbon use of hydrogen, transportation and storage of hydrogen, hydrogen technologies. "The goal of the strategy, among other things, is to accelerate the development and subsequent implementation of economically affordable hydrogen technologies," said Silvana Jirotkova, Deputy Minister of Industry and Trade. "The Czech Republic should have ambitions to become an important exporter in this area in the future." "The question of how to use hydrogen depends mainly on price, so we must look for ways to minimize costs and maximize efficiency by replacing fossil fuels with hydrogen," added Peter Merwart, Hydrogen Minister's Plenipotentiary for Industry and Trade. "Our goal is to create in the Czech Republic a new low-carbon economy that will gradually replace an economy heavily dependent on fossil fuels that will gradually decline." The Czech Republic, together with other Member States, has committed to achieving climate neutrality by 2050. The hydrogen strategy is one of the important tools to achieve this goal. Due to the geographical position of the Czech Republic, not only renewable energy sources were taken into account, but also other sources that can produce low-carbon hydrogen. Among the companies already working in this direction, the utility group CEZ is developing up to 15 projects for the production and use of hydrogen, and in six of them it is already taking concrete steps, especially in the field of using hydrogen in public transport. In addition, the University of Chemistry and Technology in Prague has an accredited curriculum focused on hydrogen technology, and the region of Usti nad Labem is the first Czech region with a developed network of filling stations, three of which will be put into operation in the near future.

Other interesting news:

▪ New technology will speed up smartphone charging by 2,5 times

▪ Solar-powered plane flying around the world

▪ Male characters in games speak twice as often as females

▪ The ocean turns to plastic

▪ Morality, charity and religion

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ website section Television. Article selection

▪ article My police protect me. Popular expression

▪ article Where did sugar come from? Detailed answer

▪ Amaryllis article. Legends, cultivation, methods of application

▪ article Power amplifier on bipolar transistors. Encyclopedia of radio electronics and electrical engineering

▪ article Where is the milk? Focus secret. Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024