It’s worth starting with the fact that the choice of alternating or direct current for conducting welding work depends on the coating of the electrode itself, as well as on the brand of metal with which you have to work. In other words, it is not always possible to use a welding converter to obtain direct current, and therefore a more stable arc for work.

What is a converter?

Converter for welding work - several devices. It uses a combination of an AC electric motor and a special DC welding machine. The process looks like this. The electrical energy supplied from the AC mains acts on the electric motor, causing the shaft to rotate, creating mechanical energy at the expense of electrical energy. This is the first part of the transformation. The second part of the operation of the welding converter is that during the rotation of the generator shaft, the generated mechanical energy will create a constant electricity.

However, it is immediately worth noting that the use of such devices is not very popular, since their efficiency is low. In addition, the engine has rotating parts, which makes it not very convenient to use.

Operating principle of the device

It can be noted that a welding converter is a specific type of ordinary one. Briefly speaking about the design of this equipment, it is approximately as follows. There are two main parts - an electric motor, which is most often asynchronous, and a DC generator. The special feature is that both of these devices are combined into one housing. It is also important to note that the circuit contains a collector. Since the operation of the generator is based on electromagnetic induction, it will produce alternating current, which will be converted into a constant one using a collector.

If we talk about it, it should not be confused with devices such as a rectifier or inverter. The end result is the same for all three devices, but the essence of their work is very different. The biggest difference is that the converter has a longer conversion chain. Since alternating current is first converted into mechanical energy and only then into direct current.

Welding converter device

You can consider the design of this device using the example of a single-station converter. Such models consist of a conventional drive asynchronous motor and are combined in one housing.

It is worth noting here that such equipment is intended to work on outdoors. However, there they must be placed either in specially designated places - machine rooms, or under canopies. This is necessary for protection electrical equipment from precipitation.

Internal structure of the unit

If we go into the details of the device and design, as well as the principles of operation of the welding converter, then it all looks like this.

Since the device heats up during operation, a fan is mounted on the shaft between the generator and the electric motor to cool the converter. The electromagnetic parts of the generator, that is, its poles and armature are made of thin sheets steel of electrical grade. The pole magnets contain elements such as coils with windings. The armature, in turn, has longitudinal grooves into which the insulated winding is placed. The ends of this winding are soldered to the collector plates. Also of this device There is a ballast and an ammeter. Both devices are located in a box.

Models used

Currently, welding converters with a rated welding current of 315 A are used. The main purpose of these units is to supply direct current to one welding station. Also it can be used to power manual arc welding, surfacing and cutting of metals with piece electrodes. Converters of this kind use generators of the GSO-300M and GSO-300 types. Their device is a four-pole self-excited DC commutator machine. The only difference between these two models is that they have different generator shaft speeds. This is regarding the 315 welding converter. 500 A is the second rated current, which is also used for operation. However, here it is already necessary to connect a more powerful converter, for example, model PD-502. The significant difference between this converter model and the GSO is that it has independent excitation. The point here is that to power the PD-502, three-phase alternating current is used, which first passes through an inductive-capacitive voltage converter. Simultaneously with the power supply function, it also acts as a stabilizer for this model of the unit.

However, it is important to understand that the main purpose of the welding converter is to convert variable electrical energy into constant electrical energy.

Types of converters

There are two main types of converters - stationary and mobile. If speak about stationary types, then most often these are small welding booths or posts designed to work with small volumes of products. The welding converters installed here are not very powerful.

Mobile ones, in turn, are designed mainly for working with large volumes. They are often used to weld water pipes, oil pipelines, metal structures, etc.

It is important to add something else about the operating principle of this device. As stated earlier - it converts alternating current into direct current using the transfer to mechanical energy. However, there are some devices that allow you to regulate the amount of DC output current. The adjustment process is carried out using devices such as ballast rheostats. The principle of operation is quite simple - the higher the resistance value set, the lower the output DC current and vice versa.

Operating rules

When using a welding converter, you must follow some rules. For example, the terminals of the device should under no circumstances be closed, since the voltage on them is 380/220 V. One more thing important rule- the converter housing must always be reliably grounded. People working directly with such equipment must be protected with gloves and masks.

Welding equipment - Welding converters

Welding converter is a combination of an AC motor and a DC welding generator. The electrical energy of the alternating current network is converted into mechanical energy of the electric motor, which rotates the generator shaft and is converted into electrical energy of direct current welding. Therefore, the efficiency of the converter is low: due to the presence of rotating parts, they are less reliable and convenient to use compared to rectifiers. However, for construction and installation work, the use of generators has an advantage over other sources due to their lower sensitivity to mains voltage fluctuations.

To power the electric arc with direct current, mobile and stationary welding converters are produced. In Fig. Figure 11 shows the device of a single-station welding converter PSO-500, mass-produced by our industry.

The single-station welding converter PSO-500 consists of two machines: a drive electric motor 2 and a DC welding generator GSO-500, located in a common housing 1. The generator armature 5 and the electric motor rotor are located on a common shaft, the bearings of which are installed in the covers of the converter housing. There is a fan 3 on the shaft between the electric motor and the generator, designed to cool the unit during operation. The generator armature is made of thin plates of electrical steel up to 1 mm thick and is equipped with longitudinal grooves in which insulated turns of the armature winding are laid. The ends of the armature winding are soldered to the corresponding commutator plates. On the poles of the magnets there are 4 coils with windings made of insulated wire, which are included in electrical circuit generator

The generator operates on the principle of electromagnetic induction. When the armature 5 rotates, its winding crosses the magnetic field lines of the magnets, as a result of which an alternating electric current is induced in the armature windings, which is converted into a direct current using the collector 6; from the brushes of the current collector 7, when there is a load in the welding circuit, the current flows from the commutator to the terminals 9.

The ballast and control equipment of the converter is mounted on housing 1 in a common box 12.

The converter is turned on by batch switch 11. Smooth control of the excitation current value and regulation of the operating mode of the welding generator is carried out by a rheostat in the independent excitation circuit using the handwheel S. Using a jumper connecting the additional terminal with one of the positive terminals from the series winding, you can install welding current for operation up to 300 and up to 500 A. Operating the generator at currents exceeding the upper limits (300 and 500A) is not recommended, since the machine may overheat and the switching system will be disrupted.

The magnitude of the welding current is determined by ammeter 10, the shunt of which is connected to the armature circuit of the generator mounted inside the converter housing.

The windings of the GSO-500 generator are made of copper or aluminum. Aluminum busbars are reinforced with copper plates. To protect against radio interference that occurs during generator operation, a capacitive filter consisting of two capacitors is used.

Before putting the converter into operation, it is necessary to check the case grounding; condition of the commutator brushes; reliability of contacts in the internal and external circuits; turn the rheostat steering wheel counterclockwise until it stops; check that the ends of the welding wires do not touch each other; install a jumper on the terminal board according to the required welding current (300 or 500 A).

The converter is started by turning on the motor in the network (batch switch 11). After connecting to the network, it is necessary to check the direction of rotation of the generator (when viewed from the collector side, the rotor should rotate counterclockwise) and, if necessary, swap the wires at the point where they are connected to the power supply network.

Safety rules for operating welding converters

When operating welding converters, you must remember:

• Motor terminal voltage of 380/220 V is dangerous. Therefore, “neither should be closed. All connections on the high voltage side (380/220 V) must only be carried out by an electrician authorized to carry out electrical installation work;
• the converter housing must be reliably grounded;
• the voltage at the generator terminals, equal to a load of 40 V, during idling of the GSO-500 generator can increase to 85 V. When working indoors and outdoors in the presence of high humidity, dust, high ambient air temperature (above 30oC), conductive floor or when working at metal structures Voltage above 12 V is considered life-threatening.

Under all unfavorable conditions (damp room, conductive floor, etc.), it is necessary to use rubber mats, as well as rubber shoes and gloves.

The danger of damage to the eyes, hands and face from the rays of an electric arc, splashes of molten metal and the protective measures against them are the same as when working with welding transformers.

Source: Fominykh V.P. Electric welding

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Welding converter: device and features

In many cases, installations are used to perform welding work, the main component of which is a step-down transformer, but there are other types of welding equipment. Mostly only professionals know what a welding converter is, but there are many processes in which their use is the only possible option.

Structural device

The welding converter is electric car, consisting of a drive electric motor and a generator, which provides the generation of current necessary to perform the work. Due to the fact that the welding generator device includes rotating parts, its efficiency and reliability are somewhat lower than those of traditional rectifiers and transformers.

But the advantage of the converter is that it produces a welding current that is practically independent of changes in the supply voltage. Therefore, its use is advisable for welding work, which has high quality requirements.

All working components of the welding converter, including ballasts, are mounted in one single housing. At the same time, there are mobile welding converters and units, as well as stationary posts. The first ones are mainly used when performing installation and construction work, the second ones are used in factory conditions.

Settings of this type can generate significant welding current (up to 500 A or more), but it is worth remembering that operation in modes exceeding the standard value for this parameter is not allowed. Operation in critical modes can lead to failure of the installation.

Converter PSO 500

The operating principle of the welding converter allows you to generate direct and alternating welding current. Very often in production you can see the PSO 500 converter, which is characterized by high reliability and performance.

Its features include following points:

• The main part of the installation is a GSO 500 welding generator that generates direct current.
• The engine rotor and the generator armature are located on the same shaft, with a fan impeller located between them, which ensures efficient cooling of the installation.
• The converter can operate in two modes - up to 300 A and 500 A.
• Smooth adjustment of the welding current is carried out using a rheostat connected to the excitation winding circuit.
• The bagger, which is used to put the unit into operation, and the control rheostat are located in one block, which is mounted on the body of the unit.

The PSO 500 welding converter is installed on a wheelbase, which provides it with good mobility. Thanks to this, the unit can be operated in the conditions of a construction or installation site.

When using welding converters, you must follow the rules safe operation electrical equipment:

• The unit housing must be grounded; all work on connecting the unit to the power supply must be carried out by a qualified electrician.
• Considering that the converter must be connected to a 220/380V network, the motor terminal box must be securely insulated and closed.

Despite the fact that the welding converter consumes more energy to perform the work (due to the presence of mechanical connections and low efficiency), it provides a stable welding current, independent of changes in the supply voltage, which improves the quality of the weld.

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Welding converter device

Single-station welding converters consist of a three-phase current drive asynchronous electric motor and a welding generator located in a common housing.

Rice. 5.1. Welding converter PSO-500: 1 - generator; 2 - body 3 - anchor; 4 - collector; 5 - current collector; b - flywheel; 7 - box; 8 - clamps; 9 - ammeter; 10 - fan; 11 - electric motor

The converters are designed to work indoors and outdoors, where they are installed in special machine rooms or, in extreme cases, under canopies for protection from precipitation. The PSO-500 converter (Fig. 5.1) consists of a housing, inside of which the electromagnetic poles of the generator are fixed. The generator armature is located on a common shaft with an asynchronous electric motor.

A fan is attached to the shaft between the generator and the electric motor, which cools the converter. The electromagnetic poles and armature of the generator consist of a set of thin electrical steel sheets. On the magnets of the poles there are coils with windings. The armature has longitudinal grooves into which an insulated winding is placed, the ends of which are soldered to the collector plates. The carbon brushes of the current collector fit tightly to the commutator. All ballasts and ammeter are located in the box. The flywheel serves to regulate the current by a rheostat connected to the excitation winding circuit. Currently, the PSO-500 converter has been replaced by a slightly improved PD-502 converter of a similar device.

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Design and scope of application of the welding converter

Specific variety welding machine, used mainly in industry, as well as in some types of construction and installation work - this is a welding converter. It is called so because it converts alternating current from a household or industrial network into direct current, which is optimal for most types of welding.

Operating principle

Despite the essence of the final result - direct current - the converter operates on a completely different principle than a rectifier or inverter. Its design involves an extended chain of energy passage. First, alternating current turns into mechanical energy, and it, in turn, is converted back into electrical energy, but of a constant nature.

Structurally, the converter consists of an electric motor, usually an asynchronous one, and a direct current generator, combined in one housing. Since a generator using the principle of electromagnetic induction also produces alternating current, the circuit contains a collector that converts it to direct current.

Equipment example

As an example, we can consider the PSO-500 welding converter, widely known in professional circles. It consists of a cigar-shaped body, on which a block with control equipment, control elements (batch switch and rheostat regulator) and contacts for connecting electrodes is mounted on top, and an asynchronous motor and generator are mounted inside on one rotating shaft, separated by a cooling fan.

There is no direct electrical connection between the generator and the engine. The motor, started from the mains supply, begins to rotate the shaft with which its rotor is connected at high speed. The generator armature is also mounted on this shaft. As a result of the rotation of the armature, an alternating current is induced in its windings, which is converted into direct current by the collector and supplied to the welding terminals.

PSO-500 is a single-station mobile type welding converter. It is mounted on a three-wheeled trolley. The amount of welding current produced by PSO-500 can reach 300 or 500 A - depending on the jumper connecting one of the terminals to the series winding of the generator.

The output current is adjusted manually using a vernier connected to a rheostat (resistance changing device). The current is monitored using a built-in ammeter.

The numerical index in the marking - 350, 500, 800, 1000 - means the maximum direct current for which this converter is designed to work. Some models, using a vernier, can be configured to produce a welding current greater than the rated one, but operation in this mode is fraught with overheating and rapid failure of the device.

Advantages

Like any other equipment, welding converters (which historically appeared much earlier than inverters) have certain advantages, and at the same time they carry a number of certain inconveniences. Their advantages include:

• high welding current - for some models, in particular PSO-500 and PSG-500, it reaches 500 A, there are also more powerful devices;
• unpretentiousness at work;
• insensitivity to input voltage changes;
• relatively high reliability with qualified maintenance;
• good maintainability, ease of service.

The current that these devices are capable of delivering can weld very thick seams, about 10-30 mm. This is another important advantage due to which welding converters are used.

Flaws

However design features They also determine the main disadvantages of welding converters, due to which they have been replaced by inverters, at least in the domestic sphere (welding work in small businesses, in the country, in the garage). First of all this:

• large dimensions and weight (it can reach half a ton or more);
• low efficiency;
• increased electrical hazard;
• noisy operation;
• need for service.

The principle of their operation - the transition of electrical energy into mechanical energy and vice versa - implies large energy costs for shaft rotation. This is due to high consumption electricity, making the device unprofitable for “home” use. In addition, the presence of parts rotating at high speed reduces the reliability of the machine. Bottleneck The cooking converter, like the electric motor itself, are ball bearings on which the shaft is mounted. They need periodic inspection and oil changes 1-2 times a year. It is also necessary to monitor the condition of the commutator and current collector brushes.

By increased electrical danger we mean the fact that before starting welding work, the converter must be grounded; according to the rules, its connection to the network must only be carried out by an electrician.

Classification

Welding converters are classified according to various parameters. Including the number of welding stations (single and multi-station) and the type of drive (from an electric motor or, for example, from an engine internal combustion). By design they can be stationary or mobile, in a single or double housing.

Converters also differ in the shape of the output characteristic. For many types of work, this classification is decisive. Based on the shape of the output characteristic, welding converters are divided into devices that produce a falling or rigid characteristic (the latter are also capable of producing a flat falling characteristic). There are also universal converters, depending on the installed switch, capable of operating in both modes.

The fact is that the specificity of welding work in shielding gases, automatic or semi-automatic, requires extremely strict output characteristics. Such converters include, for example, the PSG-500 system. Welding converters model range PSOs have a falling characteristic, PSUs are generalists capable of switching to the desired operating mode.

PSO and other types of converters with a falling characteristic are used in industry, in automatic and manual welding equipped with automatic voltage regulators.

From the point of view of applied physics, converters are also divided depending on the technology implemented in the generator. The generator can be with split poles, with separate magnetization and demagnetization windings, with demagnetization winding and independent excitation. But in practice there is no significant difference in significant technical specifications there is no difference between all these types.

Classification of welding converters and units. For DC welding, power sources are welding converters and welding units. The welding converter consists of a DC generator and a drive electric motor, the welding unit consists of a generator and an internal combustion engine. Welding units are used for work in field conditions and in cases where the supply electrical network The voltage fluctuates greatly. The generator and internal combustion engine (gasoline or diesel) are mounted on a common frame without wheels, on rollers, wheels, in the body of a car and on a tractor base.

To work in different conditions The following units are produced: ASB-300-7 - a GAZ-320 gasoline engine mounted with a GSO-300-5 generator on a frame without wheels; ASD-3-1 - diesel engine and generator SGP-3-VIII - in the same design; ASDP-500 - like the previous unit, but installed on a two-axle trailer; SDU-2 - a unit mounted on the basis of the T-100M tractor; PAS-400-VIII - ZIL-164 type engine. and generator SGP-3-VI, mounted on a rigid frame equipped with rollers for moving along flat floor. Other units are also produced that differ in design.

Welding generators can be single-station or multi-station, designed to simultaneously power several welding stations. Single-station welding generators are manufactured with falling or rigid external characteristics.

Most of the generators that complete welding units and converters (type PS and PSO) have a falling external characteristic. The PSG type converter generator has a rigid current-voltage characteristic. Universal generators are produced that allow obtaining both falling and hard characteristics (PSU type converters).

Welding converters PSO-500, PSO-ZOOA, PSO-120, PSO-800, PS-1000, ASO-2000, PSM-1000-4 and others are supplied mainly with asynchronous three-phase squirrel-cage motors in a single-case design. They have wheels for moving around the workshop or are mounted motionless on a slab.

Technical data of some converters are given in table. 51.

Design and operation of welding generators. The industry produces three types of welding generators: with independent and parallel excitation windings, demagnetizing series windings and shaded poles.

Generators with an independent excitation winding and a demagnetizing series winding (Fig. 119) are used mainly in welding converters PS0420, PSO-ZOOA, PSO-500, PSO-800, PS-1000, ASO-2000, which differ in power and design.

On the generator diagram (Fig. 199, A) two excitation windings are shown: independent N and consistent WITH, which are located at different poles. A rheostat is included in the independent winding circuit RT. The series winding is made of a large cross-section busbar, since a large welding current flows in it. A tap is made from part of its turns and placed on the switch P.

The magnetic flux of the series winding is directed towards the magnetic flux created by the independent field winding. As a result of the action of these threads, a resultant stream appears. When idling, the series winding does not work.

The open circuit voltage of the generator is determined by the current in the field winding. This voltage can be adjusted with a rheostat RT, changing the amount of current in the magnetizing winding circuit.

When loaded, a welding current appears in the series winding, creating a magnetic flux in the opposite direction. As the welding current increases, the opposing magnetic flux increases, and operating voltage decreases. Thus, a falling external characteristic of the generator is formed (Fig. 119, b).

The external characteristics are changed by regulating the current in the independent excitation winding and switching the number of turns of the demagnetizing winding.

During a short circuit, the current increases so much that the demagnetizing flux increases sharply. The resulting flow, and therefore the voltage at the generator terminals, drops to almost zero.

The welding current is regulated in two ways: by switching the number of turns of the demagnetizing winding (two ranges) and by a rheostat in the independent winding circuit (smooth control). When connecting the welding wire to the left terminal (Fig. 119, A) small currents are installed, large currents are installed on the right.

Generators with parallel magnetizing and series demagnetizing field windings belong to the system of self-excited generators (Fig. 120). Therefore, their poles are made of ferromagnetic steel, which has residual magnetism.

As can be seen from the diagram (Fig. 120, A), the generator has two windings at the main poles: magnetizing H and series-connected demagnetizing winding C. The current of the magnetizing winding is created by the armature of the generator itself, for which the third brush is used WITH located on the commutator in the middle between the main brushes A And b.

The opposite connection of the windings creates a falling external characteristic of the generator (Fig. 120, b). The welding current is smoothly regulated by a RP rheostat connected to the self-excitation winding circuit. For stepwise current regulation, the demagnetizing winding is sectioned in the same way as in a PSO type generator. The generators of welding converters PS-300, PSO-ZOOM, PS-3004, PSO-300 PS-500, SAM-400 operate according to this scheme.

A generator with shaded poles (Fig. 121) does not have a series winding. This generator has a different pole arrangement from conventional DC electrical generators. The magnetic poles do not alternate (the north is followed by the south, then again the north, etc.), and the poles of the same name are located nearby (two north and two south, Fig. 121, b). The horizontal poles Nr are called the main ones, and the vertical ones N p - transverse.

Rice. 121. Generator with split poles: a, b - basic magnetic and electrical circuits; F g i, F p i - armature magnetic fluxes, Fg - main magnetic flux, F p - transverse magnetic flux, GN - neutral, P - transverse pole winding, GL - main pole winding, RT - rheostat

The main poles have cutouts that reduce their cross-section to ensure complete saturation of the magnetic flux already at idle. The transverse poles have a large cross-section and operate in all modes with incomplete saturation. Only the main field windings are located on the main poles, and only transverse windings are placed on the transverse ones. An adjusting rheostat is installed in the circuit of transverse excitation windings RT. Both windings are connected in parallel and receive power from the brushes, i.e. the generator operates with self-excitation. The generator has two main brushes A And b and an extra brush With.

When loaded, a current appears in the armature winding, which creates a magnetic flux of the armature, which biases the main poles and demagnetizes the transverse ones. Since the main poles are completely saturated, the effect of the magnetizing flux does not affect. With an increase in welding current, the magnetic flux of the armature increases, its demagnetizing effect (against the flow of the transverse poles) increases and this leads to a decrease in the operating voltage; a falling external characteristic of the generator is created. Thus, the falling characteristic of the generator is obtained due to the demagnetizing effect of the armature magnetic flux.

Smooth control of the welding current is carried out by a rheostat in the circuit of the transverse excitation winding 1.

1 (In previously produced generators of this type (SUG-2a, SUG-26, etc.), rough adjustment of the current was carried out by shifting the brushes from the neutral.)

Generators of converters PS-300M, SUG-2ru, etc. operate according to a split-pole scheme.

Designs of single-station welding converters. Converters PS-300-1 and PSO-300 are used to power one station for welding, surfacing and cutting. The converters are designed for operating current from 65 to 340 A.

The converter welding generator is a type of generator with parallel magnetizing and series demagnetizing field windings.

The generator has steeply falling external characteristics (Fig. 120, b) and two ranges of welding currents: 65 - 200 A and when connecting the welding cable to the left terminal (+) with the full number of turns of the serial demagnetizing winding; 160 - 340 A - when connected to the right terminal (+) with part of the turns of the series winding. The circuit of the magnetizing excitation winding includes a rheostat of the RU-Zb type with a resistance of 2.98 Ohms for currents of 4.5 - 12 A, designed to regulate the welding current.

The PSG-300-1 converter is designed to power a semi-automatic welding station in shielding gas. The converter generator has a rigid external characteristic, which is created by the biasing effect of the series field winding. The independent field winding is powered by a selenium rectifier connected to the AC network through a ferroresonant stabilizer. A rheostat is included in the independent excitation winding circuit, which allows you to smoothly regulate the voltage at the generator terminals from 16 to 40 V. The converter is connected to the network using a packet switch. The limits of welding current regulation are 75 - 300 A.

Universal welding converters PSU-300, PSU-500 have both falling and rigid external characteristics. Converters of this type consist of a single-station DC welding generator and a driving three-phase asynchronous motor with a squirrel-cage rotor, located in one housing.

The GSU type welding generator is manufactured with four main and two additional poles (Fig. 122). The turns of the main magnetizing excitation winding are laid on the two main poles, which receives power from the network through a stabilizing transformer and a selenium rectifier. On the other two main poles the turns of the series field winding are laid; the magnetic flux of these poles is directed towards the main magnetizing flux. Additional pole windings are designed to improve commutation.

To obtain steeply falling external characteristics, an independent excitation winding, a series demagnetizing winding, and part of the winding turns of additional poles are turned on.

When switching to rigid external characteristics (Fig. 122, b) the series demagnetizing winding is partially switched off, but an increased number of turns of the winding of additional poles is switched on.

Changing the type of characteristic is carried out by switching the packet switch set to switchgear, and connecting the welding wires to two corresponding clamps on the terminal board.

Introduction:

Types of welding.

Electric welding.

Diagram of a metal welding arc.

Special part:

Welding converter.

Scheme of the welding converter PSO-500.

Fundamental electrical diagram welding converter PSO-500.

Generator circuit with independent excitation and demagnetizing series winding.

Welding rectifier.

Operating principle of a welding rectifier.

The concept of the design of a welding transformer and regulator.

Electrical diagram (a) and magnetic system (b) of the STN transformer in a single-case

Turning on, adjusting and turning off the welding converter.

Exploitation:

Safety rules for operating welding converters.

Safety measures for fire-fighting equipment during operation of transformers.

Conclusion.

Literature.

The technological process of obtaining a permanent connection by establishing interatomic and intermolecular bonds between the welded parts of the product during their heating (local or general) and/or plastic deformation.

Welding is used to join metals and their alloys, thermoplastics in all areas of production and in medicine.

When welding, various energy sources are used: electric arc, electric current, gas flame, laser radiation, electron beam, friction, ultrasound. The development of technology now makes it possible to carry out welding not only in industrial enterprises, but in the field and installation conditions(in the steppe, in the field, on the open sea, etc.), under water and even in space. The welding process involves a fire hazard; electric shock; poisoning with harmful gases; damage to the eyes and other parts of the body from thermal, ultraviolet, infrared radiation and splashes of molten metal.

Types of welding

Friction welding.

Friction welding, the formation of a welded joint with this type of pressure welding occurs during the mutual movement of the welded products relative to each other under the influence of pressure on them.

Spot welding.

Spot welding is one of the types of contact electric welding of metals. When spot welding, parts are heated by electric current at the point of contact and are compressed (not in all cases). And the main type of connection is an overlap welded connection, therefore spot welding has become widespread in the automotive industry, during car repairs, and for the manufacture of stamped structures.

Contact welding.

Resistance welding is one of the thermomechanical classes of welding, in which a welded joint is formed as a result of heating the products being welded and subsequent plastic deformation of the joint under the action of compressive force.

Laser welding.

Laser welding is one of the most technologically advanced welding methods; in terms of power density it is not inferior to electron beam welding, but does not require the construction of a vacuum chamber. Laser welding is carried out in a protected gas environment or in air. Unlike the electric arc and electron beam, laser ray do not affect magnetic fields- this ensures a more stable formation of the weld seam.

Arc welding.

Arc welding - the heat source for heating and melting the metal in this type of welding is an electric arc that occurs between the metal being welded and the electrode. Electrical heat acts on the edges of the parts being welded, the electrode metal melts - a weld pool is formed. When the metal hardens in the weld pool, a welded joint is created. To create an electric arc, special sources of direct or alternating current are used

Electric welding.

In electric arc welding, the heat source is an electric arc. A welding arc is an electrical discharge between two electrodes in a gaseous environment, which is accompanied by the release large quantity warmth and light.

When welding using the Benardos method, one electrode is carbon, the other is the metal being welded. When welding according to the Slavyanov method, one electrode is a metal melting rod, the other is the metal being welded. The electrodes are connected by wires to power sources - a welding machine.

Excitation - ignition of the arc - is produced by instantaneous contact of the electrodes with their subsequent separation. In the moment short circuit the current generated in the circuit quickly heats up the electrodes at the points of their contact. When one of the electrodes is moved away, they melt at the point of contact and the space between them is filled with metal vapor. The action of the arc melts the welded metal to a certain depth, called the penetration depth. The electrode metal, melted in the arc, is transferred to the base metal bath in the form of droplets of various sizes. At a high temperature of metal vapor, the ionization of the space between the electrodes is so significant that a small voltage between the electrodes (about 50 V) is sufficient to form an electric discharge.

To maintain a stable discharge - arc - continuous ionization of the arc gap is necessary. This ionization is provided by electrons emitted from the surface of the negative electrode (cathode). Free electrons located on the surface of the negative electrode in random motion, with high temperatures Under the influence electric field fly outside the cathode. Electrons moving from the cathode collide in the arc gap with molecules of vapors and gases and split them into positive and negative - ions and electrons.

The number of electrons escaping from the cathode increases and the kinetic energy imparted by it increases with increasing voltage on the electrodes. With sufficient arc voltage, mutual bombardment of the cathode positive ions and the anode with negative ions and electrons converts the kinetic energy of these particles into thermal energy. The release of thermal and light energy by the electrodes in the welding arc occurs unevenly. In this regard, the anode temperature is higher than the cathode temperature. The temperature in the axial part of the arc column reaches 6000°C.

Fig.1. Diagram of a metal welding arc: 1 - electrode; 2 - deposited metal; 3 - base metal; 4 - crater; 5 - penetration depth

When current passes through the arc gap (with a steady arc), the arc voltage (15-35 V) will be lower than the ignition voltage (55-60 V). The magnitude of the arc voltage depends on the thermal state of the arc gap, on the degree of its ionization and, mainly, on the length of the arc. The shorter the arc, the lower the voltage. The welding arc can be powered by direct or alternating current. An arc fed by alternating current is less stable due to the fact that the current in it, at a normal frequency of 50 periods, changes its direction 100 times per second, and at these moments, with low ionization of the arc gap, the arc can break. To increase the stability of an arc fed by alternating current, ionizing coatings on the electrodes and the superimposition of currents are used high frequency on the arc.

When welding with a metal electrode according to the method of N. G. Slavyanov, the molten arc metal of the electrode in the form of drops passes into a bath of molten base metal, mixes and crystallizes in it after cooling, forming a weld. Welding according to Slavyanov can be performed on direct current with direct and reverse polarity and on alternating current. The diagram of a metal welding arc is shown in Fig. 1.

studfiles.net

Welding converter.

The welding inverter is a combination of an AC motor and a DC welding generator. The electrical energy of the alternating current network is converted into mechanical energy of the electric motor, which rotates the generator shaft and is converted into electrical energy of direct current welding. Therefore, the efficiency of the converter is low: due to the presence of rotating parts, they are less reliable and convenient to use compared to rectifiers. However, for construction and installation work, the use of generators has an advantage over other sources due to their lower sensitivity to mains voltage fluctuations.

To power the electric arc with direct current, mobile and stationary welding converters are produced. In Fig. Figure 11 shows the device of a single-station welding converter PSO-500, mass-produced by our industry.

Fig. 1 Diagram of the PSO-500 welding converter

2-Electric motor

3-Fan

4-Coil Poles

5-Anchor poles

6-Collector

7-Toko pullers

8- Handwheel for current regulation

9-welding terminals

10-Ammeter

11-pack switch

12-Converter control and control equipment box

A single-station welding converter consists of two machines: a drive electric motor 2 and a DC welding generator, located in a common housing 1. The generator armature 5 and the electric motor rotor are located on a common shaft, the bearings of which are installed in the covers of the converter housing. There is a fan 3 on the shaft between the electric motor and the generator, designed to cool the unit during operation. The generator armature is made of thin plates of electrical steel up to 1 mm thick and is equipped with longitudinal grooves in which insulated turns of the armature winding are laid. The ends of the armature winding are soldered to the corresponding plates of the collector 6. On the poles of the magnets there are mounted coils 4 with windings made of insulated wire, which are included in the electrical circuit of the generator.

The generator operates on the principle of electromagnetic induction. When the armature 5 rotates, its winding crosses the magnetic field lines of the magnets, as a result of which an alternating electric current is induced in the armature windings, which is converted into a direct current using the collector 6; from the brushes of the current collector 7, when there is a load in the welding circuit, the current flows from the commutator to the terminals 9.

The ballast and control equipment of the converter is mounted on housing 1 in a common box 12.

The converter is turned on by a batch switch 11. Smooth regulation of the excitation current value and regulation of the operating mode of the welding generator is carried out by a rheostat in the independent excitation circuit by the handwheel8. Using a jumper connecting the additional terminal to one of the positive terminals from the series winding, you can set the welding current to operate up to 300 and up to 500 A. Operating the generator at currents exceeding the upper limits (300 and 500 A) is not recommended, since it is possible the machine will overheat and the switching system will be disrupted.

The magnitude of the welding current is determined by ammeter 10, the shunt of which is connected to the armature circuit of the generator mounted inside the converter housing.

The generator windings are made of copper or aluminum. Aluminum busbars are reinforced with copper plates. To protect against radio interference that occurs during generator operation, a capacitive filter consisting of two capacitors is used.

Before putting the converter into operation, it is necessary to check the case grounding; condition of the commutator brushes; reliability of contacts in the internal and external circuits; turn the rheostat steering wheel counterclockwise until it stops; check that the ends of the welding wires do not touch each other; install a jumper on the terminal board according to the required welding current (300 or 500 A).

The converter is started by turning on the motor in the network (batch switch 11). After connecting to the network, it is necessary to check the direction of rotation of the generator (when viewed from the collector side, the rotor should rotate counterclockwise) and, if necessary, swap the wires at the point where they are connected to the power supply network.

To explain the operating principle of the welding converter, let us consider a simplified electrical circuit of the PSO-500 converter (Fig. 2). Asynchronous electric motor 1 with a squirrel-cage rotor has three stator windings connected in a star circuit (380 V). Batch switch 2 is used to switch on the electric motor to a three-phase alternating current network with a voltage of 380 V. The four-pole welding generator 8 has an independent excitation winding 5 and a series demagnetizing winding 7, which ensures a falling external characteristic of the generator. Windings 5 ​​and 7 are located at different poles. The independent excitation winding 5 is powered by direct current from a selenium rectifier 4 connected to the power supply network of the electric motor windings through a voltage stabilizer (single-phase transformer) 3 and is turned on simultaneously with the start of the electric motor.

The welding current is regulated by a rheostat 6 connected to the circuit of the independent excitation winding 5. The current value is measured by an ammeter 9. The welding circuit is connected to the terminals of the board 10, on which there is a jumper that switches sections of the series winding 7 to two ranges of welding current: up to 300 A and up to 500 A. Capacitors 11 eliminate radio interference that occurs during operation of the converter.

(Fig. 2) Schematic diagram of the PSO-500 welding converter

1- Asynchronous electric motor

2- Batch switch

3- Voltage stabilizer

4- Selenium rectifier

5-winding independent excitation

6- Adjustable rheostat

7- Serial demagnetizing winding

8- Four Pole Welding Generator

9-Ammeter

10- board clamps

11- Capacitors

Schematic diagram of a welding generator with independent excitation and demagnetizing series winding.

Figure 3 shows the circuit of the GSO-500 generator with independent excitation and a demagnetizing series winding. The magnetizing independent excitation winding is powered by current from a separate source (AC mains through a semiconductor selenium rectifier), and the demagnetizing winding is connected in series with the armature winding so that the magnetic flux FR it creates is directed towards the magnetic flux Fnv of the excitation winding. The current Inv in the excitation winding, and therefore the magnitude of the magnetic flux Fnv in it, can be smoothly changed using a rheostat R. The series demagnetizing winding is usually sectioned, which allows stepwise control of the welding current by changing the number of effective ampere-turns in the winding. The open circuit voltage of the generator is determined by the current in the independent excitation winding. With an increase in welding current Iw, the magnetic flux Фр in the demagnetizing winding increases, which, acting counter to the flow Fnv of the independent excitation winding, reduces the voltage in the welding circuit, creating a falling external characteristic of the generator (Fig. 146).

The external characteristics are changed by regulating the current in the independent excitation winding and switching the number of turns of the demagnetizing winding. The welding generators of the PSO-120, PSO-800 converters operate according to this scheme. To obtain a rigid external characteristic, the series demagnetizing windings are switched so that they act in concert with the independent excitation winding. The converter generators PSG-350 and PSG-500 operate according to this scheme.

(Fig. 3) Generator circuit with independent excitation and demagnetizing series winding.

studfiles.net

Studying the welding converter

The welding electric converter is a combination of a DC generator and a DC electric motor. During operation, AC mains electricity is converted into mechanical energy of an electric motor. As a result of rotation of the generator shaft, it is converted into direct current electrical energy used for welding. The converter has a relatively low efficiency, and due to the presence of rotating elements, it is considered less reliable in comparison with the rectifier. But for construction and installation work, the use of generators has its advantages. For example, when compared with other sources, they are less sensitive to mains voltage fluctuations.

Device

The device of a welding electric converter: an electric drive motor, a generator that generates welding current. Due to the fact that the design of the generator for welding includes rotating elements, the reliability and efficiency of the device is lower than that of standard transformers and rectifiers.

The working units of the welding equipment converter, including ballasts, are housed in one housing. A distinction is made between mobile units and converters (for construction and installation work), and stationary stations (used in production). They have a little different characteristics.

Principle of operation

The operating principle of the PSO-500 mechanism provides the ability to generate direct and alternating current. Quite often, converters of the PSO-500 brand are used in production shops, as they are characterized by high technical performance and reliability.

Installation Features

• The device is based on a GSO-500 brand generator, the purpose of which is to generate direct electric current.
• Two operating modes: up to 300 A and 500 A.
• The electric motor rotor and generator armature are equipped on the same shaft. A fan impeller is placed between them, ensuring efficient cooling of the mechanism.
• The bagger, which performs the function of starting the device, and the rheostat, which regulates the work process, are placed in a single block, fixed to the body of the installation.
• To regulate the welding current, a rheostat is used, which is connected to the excitation winding circuit.

The welding converter model PSO-500 is mounted on a wheeled chassis and is lightweight. Thanks to these characteristics, the installation is quite mobile and can be used on construction sites.

Safety precautions

When using converters, you must comply with the safety requirements for electrical installations:

• the housing must be grounded; work related to connecting the unit to the electrical network must be carried out exclusively by a professional electrician;
• Considering that the equipment is connected to a power source with a voltage of 220/380 V, the motor terminal box must be closed and reliably insulated.

Despite the fact that welding converters consume more electrical energy due to low efficiency and the presence of mechanical connections, the welding current is always stable regardless of changes in the mains voltage. This makes it possible to make welds High Quality.

It is also necessary to observe the following requirements when working with the welding converter:

• mandatory grounding of the installation housing;
• A voltage of 380/220 V at the motor terminals is considered dangerous; they must be reliably insulated and covered. Connection work is carried out by an experienced electrician who has permission to work with high voltage;
• at the generator terminals under load the voltage is 40 V, at Idling the voltage of the GSO-500 generator can increase to 85 V. During the operation of the equipment in indoors With high humidity, in the presence of dust, in the open air, with elevated temperatures environment(more than 30 degrees), conductive flooring, welding materials on structures made of metal, voltage more than 12 V poses a danger to human life.

Sergey Odintsov

electrod.biz

Pereosnastka.ru

Metal welding

The design of some welding converters

Converter PSO-500. Designed for single-station manual welding and cutting, as well as mechanized submerged arc welding. The converter consists of a DC welding generator and a three-phase asynchronous electric motor. Normal operation of the converter is possible only in the direction of rotation indicated by the arrow on the generator panel.

The generator operates according to an independent excitation circuit with a series demagnetizing winding. It has four main magnetic poles. On two poles there are coils of an independent excitation winding (power winding), made a large number turns of thin wire. On the other two main poles there are coils of a series excitation winding (demagnetizing), made of a small number of turns of thick wire (bus). To ensure normal switching, the generator has two additional magnetic poles.

The box mounted on the converter housing contains a power supply unit for an independent excitation winding, an adjusting rheostat, an ammeter, and a package switch for starting and stopping the converter electric motor. The power supply unit for the independent excitation winding consists of a single-phase step-down transformer 220/80 V and a selenium rectifier connected in a single-phase bridge (full-wave) circuit.

The converter has two ranges of welding current - up to 300 A, up to 500 A. The output terminal board has four clamps. Welding wires are connected to the minus (-) and plus (+) terminals. The positive terminal is connected by a jumper to the 300 A terminal or to the 500 A terminal - this gives two current ranges. Smooth adjustment of the current in both limits is carried out by an adjusting rheostat.

The welding converter PD-501 has a similar device.

The PSO-500, PD-501 converters should not be confused with the PSG-500 converter, designed for mechanized welding with a consumable electrode in a carbon dioxide environment. All these converters are made in the same basic housing and are similar in appearance to each other. The PSG-500 converter has a rigid external characteristic, so it is impossible to use it for manual welding with coated electrodes. It is very easy to distinguish converters by the output terminal board. The PSG-500 converter has only two output terminals: negative (-) and positive (+).

Converter PSO-300. Designed for single-station manual welding and cutting. Normal operation of the converter is possible only in the direction of rotation indicated by the arrow on the generator panel.

The converter generator operates according to a parallel excitation circuit with a series demagnetizing winding. It has four main magnetic poles. On two poles there are coils of a parallel excitation winding (magnetizing), made of a large number of turns of thin wire. On the other two main poles there are coils of a series excitation winding (demagnetizing), made of a small number of turns of thick wire (bus). To ensure normal switching, the generator has two additional magnetic poles.

Rice. 1. Board of output terminals of tag generator PSO-500

The box mounted on the converter housing contains an adjusting rheostat, an ammeter, and a package switch for starting and stopping the converter electric motor.

The converter has two ranges of welding current - up to 180 A, up to 300 A. The clamp board has four clamps. Stepwise and smooth adjustment of the tsk is carried out similarly to the PSO-500 converter.

Converter 11D-305. Designed for single-station manual welding and cutting. Normal operation of the converter is possible only in the direction of rotation indicated on the end of the converter. The converter consists of a DC valve generator, a three-phase asynchronous electric motor, and control equipment.

The valve generator is a high-frequency inductor generator with a built-in rectifier unit. The power three-phase armature winding is located in the slots of the stator of the inductor generator. The field winding is attached to the generator housing and is placed between two gear packs of the generator rotor (inductor). The generator rectifier unit is assembled from silicon valves using a three-phase bridge circuit.

The control box of the converter contains ballast control equipment: a switch for starting and stopping the electric motor, a switch for welding current ranges, a power supply unit for the generator excitation winding (voltage transformer, current transformer, rectifier).

The converter has two ranges of welding current - up to 150 A, up to 350 A, which are provided by switching the three-phase winding of the generator armature. Smooth adjustment of the current within the ranges is carried out remotely using an adjusting rheostat connected to the control box.

Converter PSM-1000-4. Designed for simultaneous power supply of several manual welding stations, which are connected to the converter in parallel through ballast rheostats. Normal operation of the converter is possible only in the direction of rotation indicated on the generator panel.

The converter generator operates according to a mixed excitation circuit. It has four main magnetic poles. Coils of parallel and series excitation windings are located on all poles. Parallel winding coils have a large number of turns of thin wire, series winding coils have a small number of turns of thick wire (bus). To ensure normal switching, the generator has four additional poles.

To smoothly regulate the generator voltage, a control rheostat is used, which is connected to the parallel excitation winding circuit of the generator.

The welding current at each welding station is adjusted in stages using a ballast rheostat. All stages of the rheostat can be connected to each other in parallel using switches. With an increase in the number of switched stages, the total resistance of the ballast rheostat decreases, and the welding current increases, and vice versa.

Ballast rheostat. It is an adjustable ohmic resistance consisting of several stages. In the welding circuit, the ballast rheostat is connected in series with the arc in the cut of the wire going to the electrode. Each stage of the ballast rheostat is connected to the welding circuit using a switch located on the front wall of the rheostat. Here on the plate is the approximate value of the welding current depending on the number of switched on stages.

The elements of the resistance stages of the rheostat are made from heat-resistant fechral wire of rectangular or round section and is performed in the form of a spiral.

Ballast rheostats are produced at rated currents 200, 315, 500 A. Some brands of ballast rheostats: RB-200, RB-201, RB-300, RB-301, RB-302, RB-500, RB-501. Schematic diagram ballast rheostat is shown in Fig. 31.

If a current value greater than that for which the rheostat is designed is required, then two ballast rheostats can be connected in parallel.

Converter PSU-500. The design is similar to the PSO-500 converter. Is universal. Designed for single-station manual welding and cutting, for mechanized submerged arc welding, for mechanized welding in a carbon dioxide environment.

The converter generator has both falling and hard external characteristics. The generator is excited independently with a series demagnetizing winding.

The generator has four main magnetic poles and two additional ones. On the two main poles there are coils of an independent (magnetizing) excitation winding, made of a large number of turns of thin wire. The series (demagnetizing) field winding coils are located on the other two main poles.

To obtain a falling external characteristic of the converter, independent (magnetizing) and series (demagnetizing) excitation windings are used, as well as part of the winding turns of the additional poles of the generator.

To obtain a rigid external characteristic of the converter, part of the turns of the series (demagnetizing) field winding is turned off, but the full number of turns of the additional pole winding is turned on.

Switching of external characteristics is carried out by a packet switch and connecting the welding cables to two corresponding clamps on the terminal board.

A specific type of welding machine, used mainly in industry, as well as in some types of construction and installation work, is a welding converter.

It is called so because it converts alternating current from a household or industrial network into direct current, which is optimal for most types of welding.

Despite the essence of the final result - direct current - the converter operates on a completely different principle than a rectifier or inverter.

Its design involves an extended chain of energy passage. First, alternating current turns into mechanical energy, and it, in turn, is converted back into electrical energy, but of a constant nature.

Structurally, the converter consists of an electric motor, usually an asynchronous one, and a direct current generator, combined in one housing. Since a generator using the principle of electromagnetic induction also produces alternating current, the circuit contains a collector that converts it to direct current.

Equipment example

As an example, we can consider the PSO-500 welding converter, widely known in professional circles.

It consists of a cigar-shaped body, on which a block with control equipment, control elements (batch switch and rheostat regulator) and contacts for connecting electrodes is mounted on top, and an asynchronous motor and generator are mounted inside on one rotating shaft, separated by a cooling fan.

There is no direct electrical connection between the generator and the engine. The motor, started from the mains supply, begins to rotate the shaft with which its rotor is connected at high speed.

The generator armature is also mounted on this shaft. As a result of the rotation of the armature, an alternating current is induced in its windings, which is converted into direct current by the collector and supplied to the welding terminals.

PSO-500 is a single-station mobile type welding converter. It is mounted on a three-wheeled trolley. The amount of welding current produced by PSO-500 can reach 300 or 500 A - depending on the jumper connecting one of the terminals to the series winding of the generator.

The output current is adjusted manually using a vernier connected to a rheostat (resistance changing device). The current is monitored using a built-in ammeter.

The numerical index in the marking - 350, 500, 800, 1000 - means the maximum direct current for which this converter is designed to work. Some models, using a vernier, can be configured to produce a welding current greater than the rated one, but operation in this mode is fraught with overheating and rapid failure of the device.

Advantages

Like any other equipment, welding converters (which historically appeared much earlier than inverters) have certain advantages, and at the same time they carry a number of certain inconveniences. Their advantages include:

• high welding current - for some models, in particular PSO-500 and PSG-500, it reaches 500 A, there are also more powerful devices;
• unpretentiousness at work;
• insensitivity to input voltage changes;
• relatively high reliability with qualified maintenance;
• good maintainability, ease of service.

The current that these devices are capable of delivering can weld very thick seams, about 10-30 mm. This is another important advantage due to which welding converters are used.

Flaws

However, the design features also determine the main disadvantages of welding converters, due to which they have been replaced by inverters, at least in the domestic sphere (welding work in small businesses, in the country, in the garage). First of all this:

• large dimensions and weight (it can reach half a ton or more);
• low efficiency;
• increased electrical hazard;
• noisy operation;
• need for service.

The principle of their operation - the transition of electrical energy into mechanical energy and vice versa - implies large energy costs for shaft rotation. This results in very high power consumption, making the device unprofitable for “home” use.

In addition, the presence of parts rotating at high speed reduces the reliability of the machine. The bottleneck of the cooking converter, like the electric motor itself, is the ball bearings on which the shaft is mounted.

They need periodic inspection and oil changes 1-2 times a year. It is also necessary to monitor the condition of the commutator and current collector brushes.

By increased electrical danger we mean the fact that before starting welding work, the converter must be grounded; according to the rules, its connection to the network must only be carried out by an electrician.

Classification

Welding converters are classified according to various parameters. Including by quantity (single- and multi-station) and by type of drive (from an electric motor or, for example, from an internal combustion engine). According to their design, they can be stationary or mobile, in a single or double housing.

Converters also differ in the shape of the output characteristic. For many types of work, this classification is decisive. Based on the shape of the output characteristic, welding converters are divided into devices that produce a falling or rigid characteristic (the latter are also capable of producing a flat falling characteristic).

There are also universal converters, depending on the installed switch, capable of operating in both modes.

The fact is that the specificity of welding work in shielding gases, automatic or semi-automatic, requires extremely strict output characteristics.

Such converters include, for example, the PSG-500 system. Welding converters of the PSO model range have a falling characteristic; PSU are universal ones that can switch to the desired operating mode.

PSO and other types of converters with a falling characteristic are used in industry, in automatic and manual welding systems equipped with automatic voltage regulators.

From the point of view of applied physics, converters are also divided depending on the technology implemented in the generator. The generator can be with split poles, with separate magnetization and demagnetization windings, with demagnetization winding and independent excitation. But in practice, there is no significant difference in significant technical characteristics between all these types.