What is a welding rectifier

Let's learn in detail about the current rectifier

The operating principle of many types of welding equipment is based on the use of direct current. In order for such devices to operate from the electrical network, which, as is known, is a source of alternating current, they are equipped with special devices called rectifiers. How a modern current rectifier works and what types of it are used today in everyday life and industry - these questions will be the subject of our conversation.

Operating principle of the device

In any rectifier, regardless of its type, semiconductor elements are used, the properties of which ensure the conversion of alternating to direct. Being made from special materials, such as crystallized germanium or silicon with the addition of alloying components, these elements have the ability to conduct current in only one direction.

Let's watch a video about the device:

Modern variable flux rectifiers use three types of semiconductor parts:

Diode

The simplest version of a semiconductor element. It has two terminals called anode and cathode. The function of a diode in an electrical circuit is similar to that of a check valve in a piping system: the element passes an electric current directed from the anode to the cathode and closes as soon as the direction of the current is reversed.

The main characteristics of diodes are:

Maximum current;
The maximum voltage that a locked diode can hold (if the permissible value is exceeded, a breakdown of the diode will occur, in which the current will flow through the element in the opposite direction);
Performance or, in other words, the time it takes for the diode to close: this characteristic will determine what current frequency the element can operate with;
The percentage of electricity lost that is dissipated as heat.

Thyristor

This element is designed in a similar way, but in addition to the anode and cathode, it has a control electrode through which a signal can be transmitted to open or close. This explains the second name of the thyristor - controlled diode.

Watch the video, a simple thyristor charger:

The list of characteristics of thyristors is the same as that of diodes, only control signal parameters have been added to it. Often in electrical engineering, diodes and thyristors are called semiconductor valves.

Transistor

This semiconductor element allows, using a low-power control signal, flexible control of the amount of high-power current passed and its voltage.

The simplest version of a single-phase semiconductor rectifier is the so-called diode bridge:

As you can see, regardless of the direction of action of the electromotive force in the alternating source, the electric current at the load will always be directed in the same direction. One of the main disadvantages of this circuit is the pulsating type of rectified current, so even the simplest rectifiers cannot operate without the use of smoothing capacitor filters.

It should be noted that a welding rectifier is not called the rectifier itself in its pure form, but a device capable of delivering a stable direct current of high power, which is necessary for welding work.

Therefore, in these devices, in addition to the rectifier itself, there is also a transformer. In addition, they can be equipped with all kinds of filters, control boards, protective and measuring equipment.

If we compare welding rectifiers with converters, we can highlight several advantages:

Welding equipment design The use of a rectifier provides a more stable electric discharge arc;
The volume of splashed metal is significantly reduced;
Rectifiers have higher efficiency;
Reduced idle losses;
Provides a wider range of welding current control;
The use of a rectifier provides greater opportunities for automating the electric welding process;
The weight and dimensions of welding machines are reduced.

Types of welding rectifiers

Based on the number of phases, there are two types of alternating flow rectifiers:

Single-phase

Designed for connection to a single-phase power supply. These devices use a single-phase bridge circuit (see above for the description of the diode bridge) with full-wave rectification.

Three-phase

Powered from a three-phase electrical network. These devices are most widespread. The operation of a three-phase rectifier is based on the use of one of two types of circuits:

Three-phase bridge.

The advantage of this circuit over a single-phase one is that its implementation requires a smaller number of semiconductor elements, and the arc is more stable.

Let's watch a video about the bridge circuit:

To operate the device, a three-phase rectifier of the simplest design is used. The output of the rectifier produces a pulsating flow with a pulsation frequency of 300 Hz.

Six-phase (double three-phase) circuit.

Used in devices with current up to 500A. The secondary winding of the transformer in such a rectifier is divided into six parts, combined into two groups, each of which plays the role of a three-phase power source. To equalize the voltage between them, a choke, also called an equalizing reactor, is used.

Six-phase (double three-phase) circuit

The range of regulation of the welding flow will depend on how the primary winding is connected - “triangle” or “star”.

Ring diagram.

It differs from the one described above in the absence of an equalization reactor. In this case, semiconductor elements operate in less favorable conditions, but the power transformer is used more efficiently.

Classification by purpose and device

In addition to this classification, modern rectifiers are divided according to their design and purpose into the following types:

Classic.

This is the simplest version of a welding rectifier. The device includes three main components:

Step-down transformer: increases current;
Rectifying circuit: converts alternating current into direct current;
Capacitor block: smoothes out current ripples.

The main disadvantages of classic rectifiers are their large weight and size, as well as the short duration of the load in the cycle. The latter means that the device can work for a short time and with significant breaks necessary for cooling. Therefore, classic rectifiers are used mainly for one-time work - at home or in small workshops.

Multi-post.

These units are used in industry or on construction sites where welding work is carried out constantly and in large volumes. The device supplies high current to several welding stations at once. Each output is equipped with its own adjustment mechanism, consisting of a choke and a rheostat, which makes it possible to configure its own operating parameters at each of the posts.

The use of a multi-station rectifier allows you to reduce the cost of purchasing equipment and its maintenance.

The main disadvantage of this type of apparatus is that if it breaks down, work stops at all stations simultaneously.

Inverters.

A classic-type welding unit, even with relatively low power, is characterized by quite impressive dimensions and weight, which is primarily due to the size of the step-down transformer. It was found that with increasing frequency of alternating current, the magnetic circuit of a power transformer can be significantly reduced. This principle was the basis for the design of the inverter rectifier. The current conversion stages in this device have the following order:

Rectification of mains current with a frequency of 50 Hz;
Conversion of direct current into alternating current with a frequency of 60 - 80 kHz (fast-switching key transistors are used);
Reducing the voltage of high-frequency alternating current and, accordingly, increasing its strength;
Rectification of the output current (a diode bridge with high-speed diodes is used).

Rectifier characteristics

The main characteristics of rectifiers include:

Rated welding current, A;
Rated operating voltage, V;
Minimum welding current, A;
Minimum operating voltage, V;
Nominal load duration, %;
Cycle time.

Thanks to modern rectifiers, welding work has become much easier.

Source: http://GeneratorVolt.ru/invertornyjj/uznaem-podrobno-o-vypryamitele-toka.html

Welding rectifier: what it is and how it works - Turner Master

Among the various machines for electric arc welding, there are devices that can not only increase the current required to melt the edges of metals, but also equalize the variable voltage frequency to a constant value.

This allows for better seam formation, reduces splashing of liquid metal, and produces a more durable connection. This unit is called a welding rectifier.

How does it work and how does current conversion occur? What types of devices are there?

Rectifier - what is it?

A welding rectifier is a device consisting of several blocks in which the incoming voltage is reduced (V) and converted. At the same time, the value of A increases. As a result, the output produces a direct current of sufficient strength to weld steel and non-ferrous metals.

Two cables (+ and -) are connected to the output terminals of the device, one of which is attached to the workpiece being welded, and the second ends with a holder or torch. Depending on the specific pole of attachment to the parts being welded, the polarity and mode of operation are determined. Welding occurs by closing an arc between the surface to be joined and the end of a consumable electrode.

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Benefits of use

The use of rectifiers in production during welding processes provides several advantages over conventional transformers:

more stable arc burning;
a small amount of splashes of molten filler and base metal;
smooth seam surface with a fine scaly pattern;
better weldability of non-ferrous and alloyed metals;
saving on consumables.

Application of rectifiers

Devices with high-power direct current allow welding with coated electrodes on many types of steel. Depending on the adjustment capabilities, some units are capable of welding metals up to 50 mm thick (with edge preparation). By adjusting the rectifier back, the welder is able to make connections on thin products with a wall thickness of 1 mm.

The welding device is capable of melting both the edges of the base metal and the electrode rods. The diameter of the latter varies from 2 to 6 mm. In addition to coated electrodes, rectifiers can work with filler wire supplied from a coil. To do this, they are actively being introduced into semi-automatic devices.

Welding current converters are also used for welding with non-consumable electrodes (tungsten, carbon). In this case, the weld pool is protected with inert gases supplied to the torch through a cable channel. So, using a welding rectifier, you can weld cast iron, stainless steel, and low-carbon steel.

In addition to welding, the units are used for cutting metals with an electric arc. This action is possible due to an increase in current strength, which burns through the steel, preventing the edges of the hole from coming together again. Unlike transformers, direct current converters allow you to save electrodes for the same amount of work.

Design and principle of operation

The welding rectifier device includes several blocks that ensure the execution of the work process. The main elements of the unit are as follows:

a step-down transformer;
diodes;
cooling module;
measuring instruments;
current regulators.

The principle of operation of the rectifier is to supply alternating current to the primary winding of the step-down transformer. Due to electromagnetic induction, a voltage flow with a reduced value of V and an increased current strength A is created on the secondary winding. The idle speed of the device should not exceed 48V.

This voltage is supplied to the diodes. Silicon elements are used as the latter. A diode is a semiconductor that allows current to flow in only one direction. This eliminates the fluctuation in its frequency and a constant voltage is supplied to the welding zone.

Since the diodes heat up, radiators and a fan are located next to them. Constant blowing of cold air allows you to increase the duration of active operation of the device, without interruption for cooling.

To monitor current characteristics, an ammeter and a voltmeter are installed in the system. Many models are equipped with an overheat sensor. If V is exceeded, the protection unit is activated, disabling welding.

To adjust the current strength in accordance with the thickness of the joint being welded, several types of adjustment are used.

Methods for adjusting current in rectifiers

To change the ampere value in the welding converter, several control options are provided. Most rectifiers have step adjustment due to a sectioned connection of the primary winding. This switch is installed in the form of a handle, with two or three positions.

If it is necessary to immediately increase the current strength until it is possible to weld thick plates or cut, then part of the primary winding is “cut off” and the current flows according to a shortened circuit.

To return the voltage in the opposite direction, the circuit switches to a longer part of the primary winding, and the current becomes less, which is convenient for welding thin sheets.

In addition to the coarse adjustment affecting the transformer, rectifiers use fine tuning using a saturation choke. It is installed between the silicon diodes (rectifier block) and the step-down transformer. An inductor is a series of coils through which voltage passes. By switching the control lever, the length of the current path in the windings and its strength changes.

Most converter models have a handle on the housing cover, which drives the screw shaft and platform with the secondary winding of the transformer. Changing the distance between the windings also serves as a way to adjust the current.

The most effective for changing the welding voltage is a thyristor unit. Its implementation in the circuit allows you to control the length of the voltage supply and its effect on the metal. Thanks to thyristors, it is possible to simulate rigid, flat-sloping and steep-sloping current characteristics.

Types of devices

Rectifiers for welding have several varieties depending on the type of diode connection and the parameters of the incoming voltage. They can be divided into:

single-phase (half-wave, half-bridge and full-bridge);
two-phase (with serial and parallel connection of bridges);
three-phase (with a number of 6 to 12 diodes in parallel and series circuits).

Of the rectifiers commonly found in production, three-phase models are used, which allow you to work with metals of different thicknesses, and perform not only welding, but also cutting of materials.

There are also multi-station devices that make it possible to connect up to six electrode holders to them simultaneously.

To provide individual conditions for each worker, the circuit includes induction protection and a ballast rheostat to regulate the current on site.

In everyday life, rectifiers are used as part of welding inverters. In these devices, a step-down transformer changes the current, after which the rectifying unit produces a constant voltage.

It is then converted back to variable, but at a very high frequency. And although welding with such devices is performed using alternating current, thanks to its modernization, high-quality and even seams are obtained.

Inverters are compact and lightweight.

Maintenance and repair

In order for a welding rectifier to work well, it is necessary to carry out proper maintenance of the device and timely repairs.

The first includes checking all conductive parts for the integrity of the insulation, the reliability of the terminals, and the removal of dust from the internal elements. Before putting into operation the device must be grounded.

The screw for adjusting the stroke of the secondary winding must be periodically lubricated. Do not operate the straightener without a protective cover.

The most common breakdowns are overheating and strong noise of the device. If these symptoms are observed, this may mean:

the fan impeller does not meet the required size and needs to be replaced;
the cooling fan shaft is jammed;
the primary winding of the transformer has short-circuited and needs to be rewound;
the insulation of the core sheets or its studs is broken.

Other common rectifier failures requiring repair include a decrease in output voltage. This could be due to a short or break in the secondary winding. If the magnetic starter turns on for one second and turns off, then the reason lies in a non-working diode, or a short circuit of the current to the casing of the device.

The straightener allows you to carry out welding work to obtain better quality seams on various metals. Thanks to the conversion of current from the transformer into constant voltage, welding and cutting with a stable arc is possible, and consumables are saved.

Source: https://tokarmaster.ru/rekomendatsii/svarochnyj-vypryamitel-chto-takoe-i-kak-rabotaet.html

Welding rectifiers device and classification | Welding and Control

Based on the design of the power part, rectifiers can be divided into six groups. An earlier and simpler design is the transformer-regulated rectifier. Its power part consists of a transformer T, a rectifier unit VD on uncontrolled valves and a smoothing choke L. The transformer in such a circuit is used to reduce the voltage, form the necessary external characteristic and regulate the mode.

A rectifier with a saturation choke has found some use. The LS saturation choke is used to form an external characteristic and regulate the mode. Thyristor rectifiers are more advanced and widespread.

The thyristor rectifier unit VS, due to phase control of the moment of switching on the thyristors, provides mode regulation, and with the introduction of current and voltage feedback, also the formation of any external characteristics. Sometimes the thyristor regulator VS is installed in the circuit of the primary winding of the transformer T, then the rectifier block VD can be assembled from uncontrolled valves - diodes.

The transistor regulator VT, on the contrary, is installed in the welding current circuit; with its help it is easy to implement software control of the welding process. The inverter rectifier circuit is original. The UZ inverter converts the direct voltage of the rectifying unit VD1 into high-frequency alternating voltage, which is then lowered by the transformer T and rectified by the VD2 unit.

By influencing the parameters of the inverter, they regulate the mode and form the external characteristics of the rectifier. Any rectifier also includes a fan, start-up and control equipment. Thyristor, transistor and inverter rectifiers have more complex control circuits with circuits for generating control signals and feedback.

Rectifiers are also classified according to the type of external characteristics. When mechanized welding in carbon dioxide and submerged arcs, single-station rectifiers with rigid, as well as flat-sloping and gently increasing characteristics are used to complete devices operating on the principle of arc self-regulation. These rectifiers usually have a normal dissipation transformer.

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The rectifier regulator is used to adjust the welding voltage.

Currently, the following methods of voltage regulation are used: turn (rectifier with a transformer with sectioned windings), magnetic (rectifier with a transformer with magnetic commutation, rectifier with a saturation choke), phase (thyristor rectifier), as well as pulse (frequency, width and amplitude in transistor and inverter rectifier).

Rectifiers with steep characteristics are designed for manual welding. The requirements for such rectifiers are set out in GOST 13821-77 “Single-station rectifiers with decreasing external characteristics for arc welding.”

When compared with transformers, the main advantages of welding rectifiers as DC power sources are considered to be high ignition reliability and arc stability. Compared to rotating sources (converters and units), rectifiers have the following advantages: higher efficiency, low weight and dimensions, absence of rotating parts, high reliability.

Designs of transformers as part of welding rectifiers

In a rectifier, the transformer performs the functions of reducing the voltage, and sometimes also forming the necessary external characteristics and regulating the mode. Therefore, transformers for welding rectifiers have the same design and principle of operation as transformers. Single-phase transformers are used relatively rarely in rectifiers.

Fig.1 Designs of three-phase transformers with normal (a) and

increased (b,c) scattering

On each of the three rods of the magnetic circuit 3, one primary 1 and one secondary 2 winding of the corresponding phase are usually placed. A transformer with normal magnetic leakage (Fig. 1a) has a rigid external characteristic. When the primary and secondary windings are placed at a considerable distance from each other, a transformer with increased dissipation and a decreasing external characteristic is obtained (Fig. 1, b).

Magnetic cores shown in Fig. 1, a and b, are called asymmetrical. Indeed, the magnetic resistance along the path of the flux created by the windings of phase B is less than for phases A and C, therefore the current in phase B is higher than in phases A and C, and a harmonic component appears in the rectified current curve. A symmetrical magnetic circuit (Fig. 1c) has a more complex structure and is more expensive to manufacture.

Valves used in welding rectifiers

Mostly silicon power valves are used: uncontrolled (diodes), partially controlled (thyristors) and controlled (transistors).

Let's consider the operating principle of a diode using the example of the simplest half-wave rectification circuit (Fig. 2). In the positive half-cycle of the sinusoidal voltage of the supply network, diode V turns on in the forward direction (Fig. 2a). Since its resistance is small, the forward current ipr (Fig. 2,b) is relatively large.

Rice. 2. Oscillograms (b) and diode operation for forward (a) and reverse (c)

switching on in alternating current circuit

Almost the entire network voltage is applied to the load Rн, and the voltage drop across the diode upr does not exceed 1-2 V. In the negative half-cycle (Fig. 2, c) the diode is turned on in the opposite direction, its resistance increases sharply, and the current irev decreases almost to zero .

Almost no voltage is supplied to the load, since almost the entire network voltage is applied to the open circuit formed by the closed diode. Thus, if we neglect the insignificant reverse current irev, an intermittent current of one direction flows through the load - rectified current id = irev.

Its average value over the full period is Ipr.

Let's consider the operation of a thyristor (Fig. 3a). To unlock the thyristor, two conditions must be met. Firstly, it should be turned on in the forward direction, i.e. the potential of its anode A must be higher than the potential of the cathode K. Secondly, a voltage pulse positive relative to the cathode must be applied to its control electrode UE.

Therefore, in the positive half-cycle, the thyristor will unlock with a delay by the electrical angle a corresponding to the supply of a control pulse. Consequently, the average value of the rectified current Ipr, proportional to the shaded area, for a thyristor is less than for a diode, and also decreases with increasing turn-on delay.

It is impossible to block a conventional thyristor by removing a control pulse; it turns off only at the end of the half-cycle when the alternating voltage drops to zero. Therefore, the thyristor is called an incompletely controlled valve. During the negative half-cycle, the thyristor is locked. Thus, the thyristor can be used not only for rectification, but also for current regulation.

Rice. 3. Thyristor (a) and transistor (b) in an alternating current circuit

Power transistors have been developed relatively recently. Although they are still unreliable and expensive, widespread adoption is expected due to the unique regulatory capabilities they provide. In welding rectifiers, a circuit with a common OE emitter is promising (Fig. 3,b). Typically a transistor is used as a switch.

In the positive half-cycle, until current ib is supplied to base B in the cutoff mode until moment a1, there is practically no forward current ipr of collector K, and therefore no current in the load.

When a sufficiently large base current ib is supplied, the transistor at moment a1 will immediately go into saturation mode, in which the forward collector current ipr sharply increases to a value limited only by the supply voltage U~ and the load resistance Rн. When the base current is removed at moment a2, the forward current will also sharply decrease.

Source: https://svarkka.ru/%D0%BE%D0%B1%D1%89%D0%B8%D0%B5-%D1%81%D0%B2%D0%B5%D0%B4%D0% B5%D0%BD%D0%B8%D1%8F-%D0%BE-%D1%81%D0%B2%D0%B0%D1%80%D0%BE%D1%87%D0%BD%D1% 8B%D1%85-%D0%B2%D1%8B%D0%BF%D1%80%D1%8F%D0%BC%D0%B8%D1%82%D0%B5/

Welding rectifier: what it is and how it works

This allows for better seam formation, reduces splashing of liquid metal, and produces a more durable connection. This unit is called a welding rectifier.

How does it work and how does current conversion occur? What types of devices are there?

Reading time: 7 minutes

Now in stores you can find a welder for every taste and budget. Manufacturers offer to buy welding transformers, inverters, semi-automatic machines and, of course, rectifiers. A novice welder faces a number of difficulties when choosing his first welding machine, because he cannot understand such a large assortment. We have already told you about inverters, transformers and semi-automatic devices. It's time to talk about rectifiers.

From this article you will learn what a rectifier welding machine is, what is the principle of its operation and what are the pros/cons of this type of machine. You will also learn about some of the features of using a straightener.

general information

A welding rectifier is one of the classic types of welding equipment, along with a transformer. It has been used for more than a decade and has managed to fully reveal all its advantages and disadvantages. The main function of the rectifier is to convert alternating current into direct current in order to use it to ignite the arc and further form the seam.

A standard rectifier for MMA welding (manual arc welding using a coated electrode) consists of a power part (most often a transformer), a rectifier unit, as well as components that act as protection, startup and adjustment of the device.

This is the simplest description by which you can understand the design of a welding rectifier. Of course, in reality everything is much more complicated. Each component, be it a power transformer or a rectifier unit, consists of many additional elements.

But, despite the apparent complexity of the device, it is still much more reliable than an inverter or semi-automatic device. And all because it is not based on electronic components. But they are the ones that most often fail if you use an inverter. Phenomenal reliability is the main advantage of the rectifier compared to other devices (not counting the welding transformer).

If you wish, you can assemble a welding rectifier with your own hands at home. Of course, if you have sufficient skills. Moreover, the welding rectifier circuit is in the public domain and is easy to find if necessary.

There are many types of welding rectifiers. The main differences lie in their power part. On sale there are rectifiers based on a transformer, with a choke, with thyristors, with transistors, and even an inverter rectifier. Each type has its own advantages and disadvantages, but in reality you won’t notice any big differences when using it. So choose a device based on technical characteristics and cost.

Principle of operation

The operating principle of a welding rectifier can be described quite simply. First, the device reduces the received 380V network voltage to the open circuit voltage parameter. It then converts alternating current to direct current. And ultimately, the welding current is adjusted. You can start welding.

In this sense, transformers and rectifiers are very similar. The difference lies in the type of current received: a transformer uses alternating current for welding, while a rectifier uses direct current.

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Otherwise, both devices are similar. At the same time, cooking with direct current is much easier than with alternating current. Therefore, a transformer is the same rectifier, only even more complex to use.

Advantages and disadvantages

The advantages of rectifier welding machines mainly lie in the high reliability of the unit. The device can be used in almost any conditions, even if there is dirt, dust and other “enemies” around that can destroy the inverter in one or two minutes. You can also perform complex welding work using the rectifier. For example, welding stainless steel or non-ferrous metal.

With skillful ignition, the arc burns very stably and allows you to make a neat seam. The rectifier can also be used for most common welding technologies, ranging from MMA to TIG, MIG, MAG technologies. Another important advantage is the ability to organize several welding stations from one machine at once.

This means that several people can cook at once using just one straightener. Such a device is called a multi-station welding rectifier and is used in production.

Such a device also has disadvantages, and sometimes they are critical. The first thing you need to know is that the straightener is very heavy and clumsy. You won’t be able to throw it into the trunk and take it to the dacha alone.

There may also be difficulties in transporting the device to the construction site.

Another disadvantage is the high cost of the equipment set. The rectifier itself is not very expensive, but the accompanying equipment may not be affordable. However, we will talk about this in more detail below. Also keep in mind that the rectifier consumes a lot of electricity, and you may not be prepared for large bills.

The last minus, which can be called a plus at the same time, is the need for high qualifications to form a high-quality seam. If you are a beginner, be prepared for years of constant practice. On the other hand, if you learn how to cook with a straightener, then after that you will be able to cook with anything. And this is an undoubted advantage.

Features of use

The first thing you need to pay attention to if you want to use a rectifier at home is the voltage of your electrical network. It is unlikely that it exceeds 220V, and often the figure is even less. Of course, there are devices on sale that can operate on 220V voltage, but they are rare. Most rectifiers require 380V to operate fully. Such an electrical network is also called an industrial three-phase network. To solve this problem, you need to use a generator that produces 380V.

This is the main drawback of the rectifier. This is a powerful device that gives you a lot of possibilities, and at the same time it is not very expensive. But for it to work, you will have to buy an expensive generator and tinker with the connection every time. It is for this reason that many beginners prefer to buy a low-power inverter and plug it into an outlet, instead of struggling with a transformer or rectifier.

Also keep in mind that for stable operation it is not enough to simply connect the rectifier to 380V and start working. The rectifier (like the transformer) is very demanding on the electrical network itself. It should not only be stable, but also have a power reserve. This is necessary to ignite the arc and ensure its stable combustion.

Also keep in mind that it is not so easy to ignite an arc with a rectifier, even if everything is fine with the voltage in the network. The important thing here is to have the skill or just practice a lot. The rectifier is not equipped with additional functionality such as arc force or hot start. So you will have to light the arc based on your experience and skills.

Source: https://respect-kovka.com/chto-predstavlyaet-soboy-svarochnyy-vypryamitel/

Welding rectifier: types, models vd 306, vdm, arc, price

Any welding rectifier - universal, throttle, inverter or thyristor - operates according to the same circuit, absorbing alternating “household” current and delivering direct “welding” current.

In the process of the indicated transformation, not only the type of current changes - the rectifier increases the power, reducing the voltage. After all, welding requires a current strength that increases from the standard five to tens and hundreds of amperes, sufficient to generate an arc between the cathode and anode of the rectifier.

In this article we will look at the basics of the design of welding rectifiers using the example of the layout of specific varieties of such welding machines.

Main components of the rectifier design

Any rectifier consists of the following components: a power transformer, a rectifying unit and a ballast unit. In addition, the design of the rectifier necessarily includes a protective and measuring device.

The rectifier power transformer can be:

Three-phase (powered from an industrial power supply at 380 Volts).
Single-phase (powered from a household power supply of 220 Volts).

Moreover, the first option is preferable to the second, since three-phase transformers provide greater stability of the welding current characteristics.

The current from the transformer is transmitted to the inductor (diode), where a constant current is obtained from the alternating flow.

Moreover, in most cases, VDM type welding rectifiers are used, based on a bridge circuit that guarantees redistribution of energy in favor of the positive pole.

By transferring the “plus” to the electrode or mass cable, you can achieve melting of the joining or filler material.

In general, in terms of design, the rectifier can be thyristor, inverter, choke or transistor. And further in the text we will consider these types of welding machines in more detail.

Thyristor rectifiers

Such a device operates on a thyristor rectifying unit, which is also a current regulator. Moreover, using a phase-pulse control circuit that shifts the control pulse in time, it is possible to obtain high-precision current-voltage characteristics of the welding current.

According to this scheme, both the VDU-VGD welding rectifier and the VSVU-VSP type devices operate. Moreover, the latter operate on the basis of generating a sawtooth voltage, which is converted into rectangular pulses. And in VDU devices, thyristors are built directly into the phases of the secondary windings of power transformers.

The simplicity and versatility of the thyristor design has made this circuit the standard design used in most welding rectifiers.

Inverter rectifier

In the design of such a device, a high-frequency current is transmitted to the output of the power transformer, converted from standard alternating current with a frequency of 50 Hz by a special unit - an inverter.

This arrangement allows you to reduce the weight of the power transformer and turns the inverter rectifier into one of the lightest welding machines.

In addition, its efficiency is almost 90 percent (an absolute record among welding machines), and the operating time is 100 percent (as much as 10 minutes of continuous operation).

If the main criterion by which you choose a welding rectifier is the price of the device, then you will certainly like the inverter option. After all, its energy consumption is half that of other welding machines.

Throttle rectifier

If you need a truly reliable device, pay attention to the throttle rectifier. In this case, the voltage from the transformer is transmitted not to the rectifier bridge, but to the saturation choke, from which the current goes to the control unit and after it enters the rectifier unit. Moreover, there is still one throttle behind this block.

In fact, in this circuit, the inductor plays the role of an element of the control unit rather than part of the rectifying bridge. But such a distribution of responsibilities ensures that the main product that the welding rectifier emits - the electric discharge arc - will have stable characteristics.

Therefore, throttle devices are used in truly critical areas: in mines, at the junction of pipelines, in quarries, and so on. In addition, the choke rectifier generates a welding current of up to 650 Amps - and this is practically the peak value for electric arc or argon arc welding. For example, a fairly powerful competing device - a three-phase welding rectifier VD 306 - is capable of delivering no more than 315 Amperes.

Transistor rectifier

The transistor-based rectifying unit guarantees almost 100% accuracy in the process of adjusting the current-voltage characteristics of the welding machine.

This quality is explained by the high “response” of the transistor component of the device.

In addition, due to the high response of transistors on the rectifier, you can “set” any ratio of welding current and welding voltage. And such adjustment is available not only at the preliminary stage, during setup of the device, but also during its use.

Of course, such undoubtedly outstanding qualities could not remain unclaimed. Transistor rectifiers are used for joining particularly important (and not so important) components of pipelines, gas pipelines, ventilation systems, fastening shafts, and so on.

Source: https://steelguide.ru/svarka/svarochnoe-oborudovanie/svarochnyj-vypryamitel-universalnyj.html