The operating principle of the converter is regulation of the welding current. Welding converters. Welding generators with magnetizing parallel and demagnetizing sequential field windings

Classification of welding converters and assemblies.  For DC welding, welding transformers and welding units serve as power sources. The welding transducer consists of a direct current 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 the field and in cases where the voltage fluctuates greatly in the power supply network. The generator and internal combustion engine (gasoline or diesel) are mounted on a common frame without wheels, on rollers, wheels, in the back of a car and on the basis of a tractor.

For operation in different conditions, the following units are produced: ASB-300-7 - 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 mounted on a biaxial trailer; SDU-2 - a unit mounted on the basis of the T-100M tractor; PAS-400-VIII - engine type ZIL-164. and generator SGP-3-VI mounted on a rigid frame equipped with rollers for moving on a flat floor. Other units are also available that differ in their design.

Welding generators are single-post and multi-post, designed for the simultaneous supply of several welding posts. Single-post welding generators are manufactured with falling or rigid external characteristics.

Most of the generators that complete welding units and converters (such as PS and PSO) have a falling external characteristic. The generator of the PSG type has a rigid current-voltage characteristic. Universal generators are produced, which make it possible to obtain both incident and hard characteristics (PSU type converters).

Welding converters ПСО-500, ПСО-ЗООА, ПСО-120, ПСО-800, ПС-1000, АСО-2000, ПСМ-1000-4 and others are supplied mainly with asynchronous three-phase squirrel-cage motors in single-case design. They have wheels to move around the workshop or are mounted motionless on a plate.

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

The device and operation of welding generators.  The industry produces three types of welding generators: with independent and parallel field windings, a demagnetizing series winding and with split poles.

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

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

The magnetic flux of the series winding is directed towards the magnetic flux generated by the independent excitation winding. As a result of the action of these flows, a resulting stream appears. When idling, the sequential 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 magnitude of the current in the circuit of the magnetizing winding.

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

External characteristics are changed by adjusting the current in the independent excitation winding and switching the number of turns of the demagnetizing winding.

With a short circuit, the current increases so much that the demagnetizing flux increases sharply. The resulting flow, and therefore the voltage at the terminals of the generator, practically drops to 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 regulation). When connecting the welding wire to the left terminal (Fig. 119, a) small currents are set, on the right - large.

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

As can be seen from the diagram (Fig. 120, a), the generator has two windings at the main poles: magnetizing N and serially connected demagnetizing C. The current of the magnetizing winding is created by the armature of the generator itself, for which the third brush FROMlocated on the collector in the middle between the main brushes a  and b.

The on-off switching of the windings creates a falling external characteristic of the generator (Fig. 120, b) The welding current is continuously regulated by the RP rheostat included in the self-excitation winding circuit. For step-by-step regulation of the current, the demagnetizing winding is sectioned in the same way as in a PSO type generator. The welding transformers PS-300, PSO-ZOOM, PS-3004, PSO-300 PS-500, SAM-400 operate according to this scheme.

A generator with split poles (Fig. 121) does not have a series winding. In this generator, the pole arrangement is different from conventional electric DC generators. The magnetic poles do not alternate (the north follows 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 of Nr are called the main, and the vertical N  n - transverse.

Fig. 121. Generator with split poles: a, b - principle magnetic and electrical circuits; Ф г I, Ф п I - magnetic fluxes of the armature, Фг - main magnetic flux, Ф п - transverse magnetic flux, GN - neutral, П - winding of the transverse poles, Gl - winding of the main poles, RT - rheostat

The main poles have cutouts that reduce their cross section for full saturation with magnetic flux even at idle. The transverse poles have a large cross section and work in all modes with incomplete saturation. At the main poles, only the main excitation windings are placed, and at the transverse - only transverse. An adjustment rheostat is installed in the transverse winding circuit RT. Both windings are connected in parallel with each other and receive power from the brushes, i.e. the generator works with self-excitation. The generator has two main brushes a  and b  and extra brush from.

Under load, a current appears in the armature winding, which creates a magnetic flux of the armature, magnetizing the main poles and demagnetizing the transverse ones. Since the main poles are completely saturated, the action of the magnetizing flux does not affect. With an increase in the welding current, the magnetic flux of the armature increases, its demagnetizing effect (against the flux 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 magnetic flux of the armature.

The welding current is continuously regulated by a rheostat in the transverse excitation winding circuit 1.

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

According to the scheme with split poles, the generators of the PS-300M, SUG-2ru, etc. converters work.

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

The welding generator of the converter refers to a type of generator with parallel magnetizing and sequential 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 total number of turns of the sequential demagnetizing winding; 160 - 340 A - when connected to the right terminal (+) with part of the turns of the serial winding. A rheostat of the RU-Zb type with a resistance of 2.98 Ohms for currents 4.5 - 12 A is included in the circuit of the magnetizing field winding, designed to control the welding current.

The PSG-300-1 converter is designed to power the post of semi-automatic welding in protective gas. The converter generator has a rigid external characteristic, which is created by the magnetizing action 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 adjust the voltage at the generator terminals from 16 to 40 V. The converter is connected to the network with a packet switch. Limits of regulation of welding current 75 - 300 A.

Universal welding transducers PSU-300, PSU-500 have both falling and rigid external characteristics. Converters of this type consist of a single-post welding DC generator and a three-phase squirrel-cage induction motor in one housing.

A welding generator of the GSU type is manufactured with four main and two additional poles (Fig. 122). At the two main poles, the turns of the main magnetizing field winding are laid, which receives power from the network through a stabilizing transformer and a selenium rectifier. At 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. Windings of additional poles are designed to improve switching.

To obtain steeply falling external characteristics, an independent excitation winding, a sequential demagnetizing and part of the turns of the winding of the additional poles, is switched on.

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

Changing the type of characteristic is carried out by switching the packet switch installed on the switchgear and attaching the welding wires to two corresponding terminals on the terminal board.

Welding Equipment - Welding Converters

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

To supply DC electric arc, mobile and stationary welding converters are produced. In fig. Figure 11 shows the design of the PSO-500 single-post welding converter, commercially available by our industry.

The PSO-500 single-operator welding converter consists of two machines: a driving electric motor 2 and a GSO-500 welding DC generator located in a common housing 1. Anchor 5 of the generator and an electric motor rotor are located on a common shaft, the bearings of which are installed in the covers of the converter housing. On the shaft between the electric motor and the generator there is a fan 3, designed to cool the unit during its operation. The generator armature is drawn from thin plates of electrical steel up to 1 mm thick and 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 collector plates c. At the poles of the magnets are mounted coils 4 with windings 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 lines of force of the magnets, as a result of which an alternating electric current is induced in the armature windings, which, with the help of the collector 6, is converted to direct current; from the brushes of the current collector 7, with a load in the welding circuit, current flows from the collector to terminals 9.

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

The converter is switched on by the batch switch 11. The excitation current and the operating mode of the welding generator are continuously controlled by a rheostat in the independent excitation circuit by the handwheel S. Using the jumper connecting the additional terminal to one of the positive terminals from the serial winding, the welding current can be set for operation up to 300 and up to 500 A. The operation of the generator at currents exceeding the upper limits (300 and 500A) is not recommended, as the machine may overheat and the communication system will be disturbed ation.

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

GSO-500 generator windings are made of copper or aluminum. Aluminum tires are reinforced with copper plates. To protect against radio interference arising from the operation of the generator, a capacitive filter of two capacitors is used.

Before starting the converter into operation, it is necessary to check the grounding of the housing; condition of collector brushes; reliability of contacts in the internal and external circuit; turn the rheostat control wheel fully counterclockwise; check if the ends of the welding wires touch each other; install a jumper on the terminal board according to the required value of the welding current (300 or 500 A).

The converter is started by turning on the motor in the network (packet switch 11). After connecting to the network, it is necessary to check the direction of rotation of the generator (when viewed from the side of the collector, the rotor should rotate counterclockwise) and, if necessary, swap the wires in the place of their connection to the mains.

Safety rules for the operation of welding converters

When using welding transducers, remember:

• a voltage at the motor terminals of 380/220 V is hazardous. Therefore, “neither shall be closed. All connections from the high voltage side (380/220 V) should be carried out only by an electrician who has the right to carry out electrical work;
• the converter housing must be reliably grounded;
• the voltage at the generator terminals, equal to a load of 40 V, at idle running of the GSO-500 generator can increase to 85 V. When working indoors and outdoors in the presence of increased humidity, dust, high ambient air temperature (above 30 ° C), conductive floor or when working on metal structures, voltage above 12 V is considered life-threatening.

Under all adverse 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 by electric arc rays, splashes of molten metal and the protection measures against them are the same as when working from welding transformers.

Source: Fominykh V.P. Electric welding

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Converter for welding: device and features

In many cases, installations are used to perform welding operations, the main nodes of which are a step-down transformer, but there are other types of welding equipment. Only a professional knows about what a welding transducer is, but there are many processes in which their use is the only possible option.

Constructive device

A welding transducer is an electric machine consisting of a drive electric motor and a generator, which provides the generation of current required to perform work. Due to the fact that the device of the welding generator includes rotating parts, its efficiency and reliability are somewhat lower than that of traditional rectifiers and transformers.

But the advantage of the converter is that it generates a welding current, which is practically independent of voltage drops. Therefore, its use is advisable for welding, which are subject to high quality requirements.

All working units of the welding transducer, including ballasts, are mounted in one single housing. In this case, there are mobile welding converters and assemblies, as well as stationary posts. The first, mainly used in the installation and construction works, the second, in the factory.

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

PSO 500 converter

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

The following points can be attributed to its features:

• The main part of the installation is a GSO 500 welding generator that generates direct current.
• The rotor of the engine and the armature of the generator are located on the same shaft, with a fan impeller located between them, which provides effective cooling of the installation.
• The converter can operate in two modes - up to 300 A and 500 A.
• Stepless adjustment of the welding current is carried out using a rheostat connected to the field coil.
• The bag, which is used to turn the unit on, and the control rheostat are located in one unit, which is mounted on the unit body.

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

When operating welding transducers, the rules for the safe operation of electrical equipment must be observed:

• The unit body must be earthed without fail, all work on connecting the unit to the mains must be carried out by a qualified electrician.
• Given that the inverter must be connected to a 220 / 380V network, the terminal box of the motor must be reliably insulated and closed.

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

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Welding Converter Device

Single-post welding converters consist of a three-phase current induction electric motor and a welding generator located in a common housing.

Fig. 5.1. Welding converter ПСО-500: 1 - generator; 2- case 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 engine rooms or, in extreme cases, under awnings to protect against rainfall. 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 induction motor.

A fan is mounted on the shaft between the generator and the electric motor, which cools the converter. The electromagnetic poles and the generator armature consist of a set of sheets of electrical thin steel. Coils with windings are located on the pole magnets. The anchor has longitudinal grooves, where an insulated winding is laid, the ends of which are soldered to the collector plates. The carbon collector brushes fit snugly against the collector. All ballasts and ammeter are located in the box. The flywheel is used to regulate the current with a rheostat included in the field winding circuit. Currently, the PSO-500 converter is replaced by a somewhat improved PD-502 converter of a similar device.

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Device and scope of application of the welding converter

A specific type of welding machine, used mainly in industry, as well as in some types of construction and installation works - this is the 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 elongated chain of energy passage. First, alternating current passes 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, as a rule, asynchronous, and a direct current generator, combined in one housing. Since a generator using the principle of electromagnetic induction also generates alternating current, a collector is present in the circuit, which converts it to direct.

Hardware Example

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

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

PSO-500 refers to single-post welding converters of the mobile type. It is mounted on a three-wheeled trolley. The magnitude of the welded current issued by the PSO-500 can reach 300 or 500 A, depending on the jumper connecting one of the terminals to the serial winding of the generator.

The output current is manually controlled using a vernier associated with a rheostat (resistance change device). Current control is carried out by a built-in ammeter.

The numerical index in the marking - 350, 500, 800, 1000 - means the maximum direct current that this converter is designed to work with. Some models using the vernier can be configured to produce a welding current greater than the rated current, 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 have a number of certain inconveniences. Their advantages include:

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

The current that these devices are capable of producing can be used to cook very thick joints, of the order of 10-30 mm. This is another important advantage due to which welding transducers are used.

disadvantages

However, the design features also determine the main disadvantages of welding converters, because of which inverters replaced them, at least in the household sphere (welding work in a small business, in a country house, in a garage). First of all, these are:

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

The principle of their action - the transition of electrical energy into mechanical energy and vice versa - implies large energy costs for the rotation of the shaft. This causes a very high power consumption, making the device unprofitable for "home" use. In addition, the presence of rotating parts at high speed reduces the degree of reliability of the machine. The bottleneck of the cooking converter, as well as 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 collector and current collector brushes.

By increased electrical hazard is meant the fact that before starting welding work, the converter must be grounded, its connection to the network according to the rules should be carried out only by an electrician.

Classification

Welding transducers are classified according to various parameters. Including the number of welding stations (single and multipoint) and the type of drive (from an electric motor or, for example, from an internal combustion engine). According to their design, they can be stationary and mobile, in a single or double case.

The converters also differ in the shape of the output characteristic. For many types of work, this classification is crucial. According to the shape of the output characteristic, the welding transducers are divided into devices that produce a falling or rigid characteristic (the latter are also capable of producing a sloping one). There are also universal converters, depending on the installed switch, capable of working both in that and in another mode.

The fact is that the specificity of welding work in shielding gases, automatic or semi-automatic, requires an extremely rigid output characteristic. Such converters include, for example, the PSG-500 system. Welding converters of the PSO model range have a falling characteristic, PSUs are station wagons 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 systems equipped with automatic voltage regulators.

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

A specific type of welding machine, used mainly in industry, as well as in some types of construction and installation works - this is the 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 elongated chain of energy passage. First, alternating current passes 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, as a rule, asynchronous, and a direct current generator, combined in one housing. Since a generator using the principle of electromagnetic induction also generates alternating current, a collector is present in the circuit, which converts it to direct.

Hardware Example

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

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

There is no direct electrical connection between the generator and the engine. An engine starting from the mains starts to rotate the shaft with a high speed with which its rotor is connected.

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

PSO-500 refers to single-post welding converters of the mobile type. It is mounted on a three-wheeled trolley. The magnitude of the welded current issued by the PSO-500 can reach 300 or 500 A, depending on the jumper connecting one of the terminals to the serial winding of the generator.

The output current is manually controlled using a vernier associated with a rheostat (resistance change device). Current control is carried out by a built-in ammeter.

The numerical index in the marking - 350, 500, 800, 1000 - means the maximum direct current that this converter is designed to work with. Some models using the vernier can be configured to produce a welding current greater than the rated current, 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 have a number of certain inconveniences. Their advantages include:

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

The current that these devices are capable of producing can be used to cook very thick joints, of the order of 10-30 mm. This is another important advantage due to which welding transducers are used.

disadvantages

However, the design features also determine the main disadvantages of welding converters, because of which inverters replaced them, at least in the household sphere (welding work in a small business, in a country house, in a garage). First of all, these are:

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

The principle of their action - the transition of electrical energy into mechanical energy and vice versa - implies large energy costs for the rotation of the shaft. This causes a very high power consumption, making the device unprofitable for "home" use.

In addition, the presence of rotating parts at high speed reduces the degree of reliability of the machine. The bottleneck of the cooking converter, as well as 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 collector and current collector brushes.

By increased electrical hazard is meant the fact that before starting welding work, the converter must be grounded, its connection to the network according to the rules should be carried out only by an electrician.

Classification

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

The converters also differ in the shape of the output characteristic. For many types of work, this classification is crucial. According to the shape of the output characteristic, the welding transducers are divided into devices that produce a falling or rigid characteristic (the latter are also capable of producing a sloping one).

There are also universal converters, depending on the installed switch, capable of working both in that and in another mode.

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

Such converters include, for example, the PSG-500 system. Welding converters of the PSO model range have a falling characteristic, PSUs are station wagons 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 systems equipped with automatic voltage regulators.

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

Depending on the technological process, namely the type of metal being welded and the type of electrode coating for welding, work is performed either with alternating or with direct current. The direct current from the AC compares favorably with the fact that the arc burns much more stably. This means that the welding process is easier to carry out, and it is possible to carry out the welding process even at low currents. To stabilize the current, a welding transformer, a transformer are used.

Placement of sources for welding can be individual or centralized. When grouped, equipment is placed at a distance of about 30 - 40 meters from the post, and the power supplies themselves are placed at a minimum distance from the welder.

The concept of a welding transducer.

The welding transducer is a combination of an alternating current electric motor and a special direct current welding unit. In the converter, electric energy from the AC network is transferred to the mechanical energy of the device’s electric motor, the generator shaft rotates, as a result of which a constant electric current is generated. The efficiency of the converter is not very large, and they also have rotating parts, as a result of which they are less reliable in their use and not so convenient.

However, we note that during construction and installation works, the use of converters is more priority, since they are less sensitive to voltage fluctuations in the network. To power the welding arc with direct current, both mobile and stationary converters are used.

The welding transducer has two parts - a drive electric motor and a welding generator, which are combined under one housing.

The converter armature and its rotor are located on a common shaft, the bearings of which are fixed to the converter cover housing. Also, a fan is located on the shaft between the electric motor and the generator, which cools the entire system and protects it from overheating. The operation of the converter is based on electromagnetic induction.

Stationary and mobile converters.

So, welding converters can be stationary or mobile. Posts for welding stationary products are located in small welding booths. As a rule, stationary posts have for welding small items.

Mobile posts are used for welding sufficiently large structures: water and oil pipelines, metal structures, etc. At the same time, to protect workers from the negative effects of ultraviolet rays propagating from the welding arc, shields are installed about a meter and a half high, they are made of non-combustible materials.

It is rational to use welding transducers for large volumes of welding work.

The welding transducer creates a direct current for welding, and the direct current value itself is regulated by ballast rheostats. Mobile welding stations are usually used for installation and repair work. At the same time, the welding converter is installed in trailers or closed cars, they are equipped with knife switches, which are then connected to the equipment.

Safety rules when working with converters.

When operating the converter, you need to know the following rules for working with these devices:

• The voltage at the device terminals is 380/220 volts, therefore, under no circumstances should the terminals be closed. Note that all connections from the high voltage side in the converter must be carried out by an electrician authorized to carry out this type of work.
• The transmitter housing must always be reliably grounded.
• The voltage at the generator terminals of 40 V idling can increase to 85 V. If there is a conductive floor, work at high air temperature, high humidity, dust, voltage above 12 V can be life-threatening for workers.
• With increased humidity in the room, the presence of conductive current and other factors that increase the likelihood of electric shock, it is necessary to use rubber gloves, boots with rubber soles.
• The face and eyes of workers should always be protected with helmets and shields.

Concluding, we can say that the converter is used to turn alternating current into direct current by transferring energy from one state to another. It is necessary to take into account the danger of converters and take the necessary measures to protect workers from the danger of electric shock to workers.

CHAPTER XI

DC WELDING POWER SUPPLIES

§ 49. SINGLE-POST AND MULTI-POST POWER SUPPLIES

DC power supplies are divided into two main groups: welding transformers of a rotating type (welding generators) and welding rectifier plants (welding rectifiers).
DC generators are subdivided: by the number of powered posts - into single-post and multi-post; by the installation method - on stationary and mobile; by the nature of the drive - to generators with electric drive and to generators with internal combustion engines; by design - for single-hull and two-hull.
In the form of external characteristics, welding generators can be with falling external characteristics; with rigid and dipping characteristics; combined type (universal generators, when switching windings or control devices of which it is possible to obtain falling, rigid or dipping characteristics).
The most widely used are generators with falling external characteristics, operating according to the following three main schemes:
generators with independent excitation and demagnetizing series winding;
generators with magnetizing parallel and demagnetizing sequential field windings;
split pole generators.
None of the three types of generators with falling external characteristics are notable for significant advantages in terms of both technological and energy and weight indicators.
Independent Excitation Generators with Demagnetizing Serial Coil  (Fig. 71, a). Generator G  has two field windings: independent field winding BUTfed from a separate source through an AC network and a semiconductor rectifier, and a serial demagnetizing winding ROconnected in series with the armature winding. The current in the independent excitation circuit is regulated by a rheostat R. Magnetic current F  n created by a winding of independent excitation is opposite in direction to the magnetic flux F  p demagnetizing winding. When idling, i.e. when the welding circuit is open, e. d.s generator is determined by the formula

E \u003d C  n

where E  - E.d. from. (electromotive force);
FROM  - constant component of the generator;
F  n - magnetic flux of the winding of independent excitation.

With a closed circuit, the welding current passes through the series winding. ROcreating magnetic flux F  p opposite to the magnetic flux F  n Resulting stream F  the cut represents the difference in flows:

F  rez \u003d F  n - F  p.

With increasing current in the welding circuit F  p will increase, and F  rez, e. d.s and the voltage across the terminals of the generator is to fall, creating a falling external characteristic of the generator.
The welding gok in the generators of this system is regulated by rheostats R  and sectioning the serial winding, i.e. changes in the number of ampere turns.
The domestic industry produces welding converters PSO-120, PSO-500, PSO-800, ASO-2000, equipped with generators with independent excitation and a sequential demagnetizing winding GSO-120, GSO-500, GSO-800 and SG-1000-II.
The main technical data of converters with generators operating according to this scheme are given in table. 27.

Table 27

Technical characteristics of PSO-120, PSO-800, PSO-500, ASO-2000 converters

To obtain a tough external characteristic, the successive demagnetizing windings are switched so that they act in concert with the independent excitation winding. According to this scheme, welding transformers PSG-350, PSG-500 with generators GSG-350 and GSG-500 work respectively.
The main technical data of converters with generators operating according to this scheme are given in table. 28.

Table 28

Technical characteristics of PSG-350, PSG-500 converters

Generators with magnetizing parallel and demagnetizing sequential field windings (Fig. 71.6). A distinctive feature of generators of such a scheme is the use of the principle of self-excitation. For this, there are two field windings ( BUT  and RO) - as a result of e. d.s the generator is induced by a magnetic flux of a winding connected to the brushes of the generator a  and from. The voltage between these brushes is almost constant in magnitude, so the magnetic flux F  n practically does not change. Generator winding BUT  called an independent excitation winding.
Under load (during welding), welding current passes through the winding ROincluded so that its magnetic flux F  p directed against magnetic flux F  n windings of independent excitation. With increasing current in the welding circuit, the demagnetizing effect of the series winding increases RO, and the voltage of the generator becomes less, since the emf C., induced in the winding of the generator armature, depends on the resulting magnetic flux of the generator.
Short circuit magnetic flux F  p and F  n are equal, the voltage at the terminals of the generator is close to zero.
The falling external characteristic is obtained due to the demagnetizing effect of the winding RO. Smooth control of the welding current in the generators of this system is carried out by rheostats R. It is also possible additional regulation of the welding current by switching the turns of the series excitation winding.
The scheme allows four-pole execution of generators, which allows to simplify the design and, accordingly, reduce weight.
The most common converters PSO-ZOO, PSO-500, PS-500 with generators GSO-ZOO, GSO-500, GS-500 and some other welding units work according to this scheme. The main technical data of converters with generators operating according to this scheme are given in table. 29.

Table 29

Technical characteristics of PSO-300, PSO-500, PS-500-II converters

Split pole generators  (Fig. 72). For generators of this group, falling external characteristics are obtained as a result of the demagnetizing effect of the magnetic flux of the armature winding (armature reaction). Generator G  has four main magnetic poles N 1 , N 2 , S 1 , S  2 and three groups of brushes a, b, c  on the manifold. In contrast to the considered generators, in which the north and south magnetic poles alternate with each other, the generators of this group have the same poles next to each other.

We consider each pair of poles of the same name one, but split into two. Split-pole generators are actually bipolar. Vertically positioned poles are called transverseand horizontal - the main. The main poles have cutouts to reduce the cross-sectional area and always work at full magnetic saturation, i.e. the magnetic flux generated by these poles remains unchanged at all loads. Magnetic flux of poles generated by windings NG  and NP  can be divided into two streams F  g and F  n, closing through certain pairs of poles. One magnetic flux is directed from the north pole N  1 to the south S  1 and the second - from the north pole N  2 to the south S  2. E.s. anchors depend on the intensity of magnetic fluxes F  n and F  d. The more intense the magnetic flux intersected by the conductors of the armature, the more e. d.s
When an electric arc is excited, a current passes through the armature winding, which creates a magnetic flux of the armature winding (shown by dashed lines). This magnetic flux depends on the current: the smaller the current in the armature winding, the lower the magnetic flux of the armature. The magnetic flux of the armature, which coincides in direction with the magnetic flux N 2 , S  2 main poles (the directions of the magnetic fluxes of the poles are shown by arrows), increases it; magnetic flux directed in the opposite direction F  n - reduces it.
The main poles always work at full magnetic saturation. Consequently, the magnetic flux of the armature can hardly increase the magnetic flux F  g, it can only reduce the magnetic flux of the transverse poles F  n. At the time of a short circuit in the welding circuit, the magnetic flux of the armature has the largest value and reduces the resulting magnetic flux to zero, therefore, e. d.s generator is also zero.
If there is no load in the welding circuit (at idle), there is no current in the armature winding, the armature magnetic flux is also absent, therefore, the flux F  n and, consequently, the resulting magnetic flux have the largest magnitude, and the generator has the largest voltage. Thus, due to the demagnetizing effect of the magnetic flux of the armature winding (armature reaction), a falling external characteristic is created.
According to this scheme (with split poles), PS-300M, PS-300M-1, PS-300T converters with SG-300M, SG-300M-1, SG-300T generators and some other welding units were used in industry.
The main technical data of converters with generators operating according to this scheme are given in table. thirty.

Table 30

Technical characteristics of the PS-300M, PS-300M-1, PS-300T converters

Transverse field generators.  For generators of this type, a falling external characteristic is provided by the demagnetizing effect of the armature magnetic field, and a group of various external characteristics is carried out by changing the air gap in the magnetic circuit.
Converters for welding in shielding gases.  For automatic and semi-automatic welding in shielding gases, welding transducers are required that provide rigid or increasing external characteristics. For this purpose, the industry produces PSG-350, PSG-500 converters, as well as universal PSU-300 and PSU-500 converters. Universal converters of the ПСУ type are also intended for manual arc welding, surfacing and cutting of metals with direct current, since they provide steeply dipping external characteristics.
In fig. 73 shows the external characteristics of the PSU-300 converter.

The PSG-500 converter is structurally designed in the same way as the PSO-500 converter described above. The PSG-500 converter (Fig. 74) has a single-case design.

The motors of these converters are the same and differ only in the measuring device. The PSG-500 converter generator has two excitation windings at the main poles: one independent and the other sequential, magnetizing. The electrical circuit of the PSG-500 converter is shown in Fig. 75.

The independent excitation winding is powered by an alternating current main through a ferroresonant voltage stabilizer and a block of selenium rectifiers Sun, providing a constant, independent of fluctuations, mains voltage, excitation voltage. The voltage at the terminals of the generator is continuously adjustable between 15 - 40 in  rheostat Rconnected in series to the field winding circuit. The generator armature has a low inductance, so that when the electrode is shorted to the product, the welding current increases rapidly. Current control limits 60 - 500 a.
The main technical data of PSG converters are given in table. 31.

Table 31

Technical data of PSG-350, PSG-500 converters

Universal welding converters.  For manual arc welding and welding on automatic machines equipped with automatic voltage regulators that automatically affect the feed speed of the electrode wire, power sources with falling external characteristics are required. To power automatic machines and semiautomatic devices with a constant feed rate of the electrode wire, including welding in carbon dioxide and flux-cored wire EPS-15, generators with rigid external characteristics are required. Since mechanized welding methods are used in combination with manual arc welding at factories and assembly sites, universal sources are required that provide both falling and rigid external characteristics. For this purpose, the design of the universal welding transformer PSU-300 was developed, the generator of which has one excitation winding. External characteristics in this generator are created using a triode PTincluded in the field winding circuit OV, and feedback on the load current (Fig. 76). It is a four-pole normal current generator. Its field winding OV  placed on four main poles and powered by a control device located on the converter housing.

The welding circuit and the field coil are connected by a stabilizing transformer T  p designed to provide dynamic properties of the generator.
The value of the welding current is regulated by a rheostat - regulator Dpmounted on the front of the control. As the welding current increases, the resistance of the triode increases, the excitation current decreases, and e decreases. d.s generator, i.e., the characteristic is falling. When switching control circuits, the external characteristic becomes rigid.
The main technical data of universal converters are given in table. 32.

Table 32

Basic technical data for universal converters

Transistor power sources are beginning to be used for non-consumable electrode welding of various metals and alloys at constant current in the normal and pulsating mode. The following types of transistor power sources are currently available: AP-4, AP-5 and AP-6. They provide reliable excitation and high stability of the welding arc burning and have stepless regulation of the welding current.
The main technical data of transistor power supplies are given in table. 33.

Table 33

Technical Data of Transistor Power Supplies

Multi-post welding converters.  They are designed for the simultaneous supply of several welding stations. The PSM-1000 multi-post converter is widely used in industry.
The converter has a single-case version of the stationary type (Fig. 77) and consists of a three-phase asynchronous motor AV-91-4 with a squirrel-cage rotor and a six-pole generator SG-1000 with mixed excitation. In addition to the shunt winding, a series winding is placed at the main poles to maintain a constant voltage with increasing load. The generator has a tough characteristic. The voltage is regulated by a rheostat connected to the parallel field winding circuit.

The falling external characteristic necessary for manual arc welding is created independently at each welding station by a ballast rheostat of the type RB  (This rheostat allows you to stepwise change the value of the welding current). The wiring diagram for the PSM-1000 converter and ballast rheostats is shown in Fig. 78.

The main disadvantage of multi-post converters is the low efficiency of welding posts. The advantages of multi-post converters include: ease of maintenance, low cost of equipment, a small area for equipment placement and high reliability in operation.
Ballast rheostats. The ballast rheostat serves for stepwise regulation of the value of the welding current. It consists of several resistance elements made of a constantan wire with high ohmic resistance and included in the welding circuit using knife switches.
The diagram of the most common ballast rheostat RB-300 is shown in Fig. 79. Welding current is regulated by a ballast rheostat RB-300 in the range from 15 to 300 a.

If welding requires a current value of more than 300 a, then two ballast rheostats should be included in parallel. When two rheostats are connected in parallel, the current strength increases by a factor of 2, i.e., for two RB-300 rheostats, the maximum current will be 600 a.