Many modern devices have the ability to adjust their parameters, including current and voltage values. Due to this, you can configure any device in accordance with specific operating conditions. For these purposes, there is a current regulator available in various configurations and designs. The adjustment process can occur with both direct and alternating current.

The main operating elements of regulators are thyristors, as well as various types of capacitors and resistors. In high-voltage devices, magnetic amplifiers are additionally used. Modulators ensure smooth adjustments, and special filters help smooth out interference in the circuit. As a result, the electric current at the output becomes more stable than at the input.

Current and voltage regulator

DC and AC regulators have their own characteristics and differ in their main parameters and characteristics. For example, a DC voltage regulator has higher conductivity with minimal heat loss. The basis of the device is a diode-type thyristor, which provides a high pulse supply due to accelerated voltage conversion. Resistors used in the circuit must withstand a resistance value of up to 8 ohms. Due to this, heat losses are reduced, protecting the modulator from rapid overheating.

The DC regulator can function normally at a maximum temperature of 40 0 ​​C. This factor must be taken into account during operation. Field-effect transistors are located next to thyristors, since they only pass current in one direction. Due to this, the negative resistance will be maintained at a level not exceeding 8 ohms.

The main difference of the current regulator is the use of exclusively triode-type thyristors in its design. However, field-effect transistors are used the same as in DC regulators. Capacitors installed in the circuit perform only stabilizing functions. High-pass filters are very rare. All problems associated with high temperatures are solved by installing pulse converters located next to the modulators. AC regulators whose power does not exceed 5 V use low-pass filters. Cathode control in such devices is performed by suppressing the input voltage.

During adjustments in the network, smooth operation must be ensured. At high loads, the circuit is supplemented with reverse direction zener diodes. To connect them together, transistors and an inductor are used. Thus, the current regulator on the transistor performs current conversion quickly and losslessly.

Special attention should be paid to current regulators designed for active loads. The circuits of these devices use triode-type thyristors, capable of passing signals in both directions. The anode current in the circuit decreases during the period when the maximum frequency of this device decreases. The frequency may vary within the limits set for each device. The maximum output voltage will depend on this. To ensure this mode, field-type resistors and conventional capacitors capable of withstanding resistance up to 9 Ohms are used.

Very often, such regulators use pulsed zener diodes that are capable of overcoming the high amplitude of electromagnetic oscillations. Otherwise, as a result of a rapid increase in the temperature of the transistors, they will immediately become inoperative.

Voltage and current regulator circuit

Before considering the voltage regulator circuit, it is necessary to at least become familiar with the principle of its operation. As an example, we can take voltage, which is widespread in many circuits.

The main part of such devices as the welding current regulator is the thyristor, which is considered one of the powerful semiconductor devices. It is best suited for high power energy converters. The control of this device has its own specifics: it opens with a current pulse, and closes when the current drops almost to zero, that is, below the holding current. In this regard, thyristors are mainly used to operate with alternating current.

You can regulate alternating voltage using thyristors in different ways. One of them is based on skipping or prohibiting entire periods or half-cycles from the controller output. In another case, the thyristor turns on not at the beginning of the voltage half-cycle, but with a slight delay. At this time, the output voltage will be zero, and accordingly no power will be transferred to the output. In the second part of the half-cycle, the thyristor will already conduct current and voltage will appear at the output of the regulator.

The delay time is also known as the opening angle of the thyristor. If it is set to zero, all input voltage will go to the output and the voltage drop across the on-SCR will be lost. When the angle begins to increase, the output voltage will decrease under the action of the thyristor regulator. Therefore, if the angle is 90 electrical degrees, the output will be only half the input voltage, but if the angle is 180 degrees, the output voltage will be zero.

The principles of phase regulation make it possible to create not only a current and voltage regulator for the charger, but also stabilization, regulation, and soft start circuits. In the latter case, the voltage increases gradually, from zero to the maximum value.

Based on the physical properties of thyristors, a classic current regulator circuit was created. In the case of using coolers for diodes and a thyristor, the resulting regulator will be able to supply up to 10 A to the load. Thus, at a voltage of 220 volts, it becomes possible to regulate the voltage on a load with a power of 2.2 kW.

Such devices consist of only two power components - a thyristor and a diode bridge, designed for a current of 10 A and a voltage of 400 V. The diode bridge converts alternating voltage into a unipolar pulsating voltage. Phase adjustment of half-cycles is performed using a thyristor.

To limit the voltage, two resistors and a zener diode are used. This voltage is supplied to the control system and is 15 volts. The resistors are connected in series, thereby increasing the breakdown voltage and power dissipation. Based on the simplest parts, you can easily make homemade current regulators, the circuit of which will be quite simple. As a specific example, it is worth taking a closer look at the thyristor welding current regulator.

Diagram of a thyristor welding current regulator

The principles of arc welding are known to everyone who has encountered welding work. To obtain a welding joint, you need to create an electric arc. It occurs at the moment when voltage is applied between the welding electrode and the material being welded. Under the action of the arc current, the metal melts, forming a kind of molten bath between the ends. When the seam cools, both metal parts are firmly connected to each other.

In our country, the alternating current frequency is 50 Hz, the phase supply voltage is 220 V. Each welding transformer has two windings - primary and secondary. The transformer secondary voltage or secondary voltage is 70V.

Welding can be carried out manually or automatically. At home, when you create a current and voltage regulator with your own hands, welding work is performed manually. Automatic welding is used in industrial production for large volumes of work.

Manual welding has a number of parameters that are subject to change and adjustment. First of all, this concerns the strength of the welding current and arc voltage. In addition, the speed of the electrode, its brand and diameter, as well as the number of passes required per seam may vary. In this regard, the correct selection of parameters and maintaining their optimal values ​​throughout the entire welding process is of great importance. Only in this way can a high-quality welded joint be ensured.

Changing the current during welding can be done in various ways. The simplest of them is to install passive elements in the secondary circuit. In this case, a resistor or inductor is connected in series to the welding circuit. As a result, the arc current and voltage changes due to the resistance and the resulting voltage drop. Additional resistors allow you to soften the current-voltage characteristics of the power supply. They are made from nichrome wire with a diameter of 5-10 mm. This method is most often used when it is necessary to make a current regulator. However, this design has a small range of adjustments and difficulties in adjusting parameters.

The next adjustment method involves switching the number of turns of transformer windings. Due to this, the transformation coefficient changes. These regulators are easy to manufacture and operate; you just need to make taps when winding turns. For switching, a switch is used that can withstand high current and voltage values.

Often adjustments are made by changing the magnetic flux of the transformer. This method is also used when you need to make a current regulator yourself. In this case, adjustment is made by moving the windings, changing the gap, or introducing a magnetic shunt.

The design of a convenient and reliable DC regulator is proposed. Its voltage range is from 0 to 0.86 U2, which allows you to use this valuable device for various purposes. For example, for charging high-capacity batteries, powering electric heating elements, and most importantly - for welding with both a conventional electrode and stainless steel, with smooth current regulation.

Schematic diagram of a DC regulator.

A graph explaining the operation of a power unit made according to a single-phase bridge asymmetrical circuit (U2 is the voltage coming from the secondary winding of the welding transformer, alpha is the opening phase of the thyristor, t is time).

The regulator can be connected to any welding transformer with secondary winding voltage U2=50. 90V. The proposed design is very compact. The overall dimensions do not exceed the dimensions of a conventional unregulated bridge type rectifier; for welding with direct current.

The regulator circuit consists of two blocks: control A and power B. Moreover, the first is nothing more than a phase-pulse generator. It is made on the basis of an analogue of a unijunction transistor, assembled from two semiconductor devices of n-p-n and p-n-p types. Using variable resistor R2, the direct current of the structure is regulated.

Depending on the position of the slider R2, the capacitor C1 is charged here up to 6.9 V at different rates. When this voltage is exceeded, the transistors open sharply. And C1 begins to discharge through them and the winding of the pulse transformer T1.

A thyristor, to the anode of which a positive half-wave approaches (the impulse is transmitted through the secondary windings), opens at the same time.

As a pulse one, you can use industrial three-winding TI-3, TI-4, TI-5 with a transformation ratio of 1:1:1. And not only these types. For example, good results are obtained by using two two-winding transformers TI-1 with a series connection of the primary windings.

Moreover, all of the above types of TIs make it possible to isolate the pulse generator from the control electrodes of the thyristors.

There is only one “but”. The pulse power in the secondary windings of the TI is not sufficient to turn on the corresponding thyristors in the second (see diagram), power block B. The way out of this “conflict”9raquo; The situation was found to be elementary. To turn on the powerful ones, low-power thyristors with high sensitivity to the control electrode are used.

Power block B is made according to a single-phase bridge asymmetrical circuit. That is, the thyristors work here in one phase. And the arms on VD6 and VD7 work as a buffer diode during welding.

Installation? It can also be mounted, based directly on a pulse transformer and other relatively “large-sized”9raquo; elements of the circuit. Moreover, the radio components connected to this design are, as they say, minimum-minimorum.

The device starts working immediately, without any adjustments. Get yourself one - you won't regret it.

A. CHERNOV, Saratov. Modeler-constructor 1994 No. 9.

Category: “Electronic homemade products”

Simple electronic welding current regulator, diagram

Often you have to weld metal of different thicknesses and use electrodes of different diameters, and in order for the welding to be high-quality, it is necessary to adjust the welding current so that the seam lies evenly and the metal does not splash. But, regulating the current of the secondary winding of a welding transformer is quite problematic, because it can reach up to 180-250A.

As an option, nichrome spirals are used to regulate the welding current, including them in series in the circuit of the primary or secondary winding of the welding transformer, or chokes. It is inconvenient to regulate the current in this way, and the regulator itself is cumbersome. But there is another way out - to make an electronic welding current regulator that would regulate the current in the primary winding of the welding machine.

The welding current regulator for a homemade welding machine is also very useful in cases where you have to weld metal in places where the power grid is weak, for example in villages. As a rule, they limit the current consumption for each house by installing an input circuit breaker of 16 A, i.e. You cannot turn on a load of more than 3.5 kW. A good welding machine, welding with electrodes with a diameter of 4-5 mm, consumes 6-7, or even 8 kW.

Therefore, we reduced the welding current and at the same time reduced the current consumption of the welding machine, thus investing in those 3.5 kW and “C” welding what you need.

Here is a simple circuit of such a regulator with 2 thyristors and it has a minimum of non-scarce parts. It can be done with 1 triac, but, as practice has shown, it is more reliable with thyristors.

The welding current regulator works as follows: a regulator is connected in series to the primary winding circuit, which consists of two controlled thyristors VS1 and VS2 (T122-25-3, or E122-25-3), for each half-wave. The opening moment of the thyristors is determined by the RC circuit (R7, C1, C2). By changing the resistance R7, we change the opening moment of the thyristors and thereby change the current in the primary winding of the transformer, and therefore the current in the secondary winding also changes.

Transistors can be used of the old type - P416, GT308, their lekko can be found in old receivers or televisions, and capacitors are used like MBT or MBM for an operating voltage of at least 400 V.

Transistors VT1, VT2 and resistors R5, R6, connected as shown in the diagram, are an analogue of dinistors and in this embodiment they work better than dinistors, but if you really want, instead of VT1, R5 and VT2, R6 you can put ordinary dinistors - type KN102A.

When assembling and setting up the welding current regulator, do not forget that control occurs under a voltage of 220V. Therefore, in order to prevent electric shock, all radio elements, as well as thyristor heat sinks, must be insulated from the housing!

In practice, the above electronic welding current regulator has proven itself to be excellent.
The basis was taken from the magazine Radioamator. - 2000. - No. 5 “Do-it-yourself welding transformer.”

Recently I talked with my teacher at the university, and to my misfortune, I revealed my amateur radio talents. In general, the conversation ended with the fact that I undertook to assemble a man a thyristor rectifier with a smooth current regulator for his welding “donut”. Why is this necessary? The fact is that alternating voltage cannot be welded with special electrodes designed for constant use, and given that welding electrodes come in different thicknesses (most often from 2 to 6 mm), the current value must be proportionally changed.

When choosing a welding regulator circuit, I followed the advice of -igRomana- and settled on a fairly simple regulator, where the current is changed by applying pulses to the control electrodes, generated by an analogue of a powerful dinistor, assembled on a KU201 thyristor and a KS156 zener diode. See the diagram below:

Despite the fact that an additional winding with a voltage of 30 V was required, I decided to make it simpler, and in order not to touch the welding transformer itself, I installed a small additional one of 40 watts. Thus, the attachment-regulator has become completely autonomous - it can be connected to any welding transformer. I assembled the remaining parts of the current regulator on a small board made of foil PCB, the size of a pack of cigarettes.

As a base I chose a piece of vinyl plastic, onto which I screwed the TC160 thyristors themselves with radiators. Since there were no powerful diodes at hand, we had to force two thyristors to perform their function.

It is also attached to a common base. Terminals are used to input the 220 V network, the input voltage from the welding transformer is supplied to the thyristors through M12 screws. We remove the constant welding current from the same screws.

The welding machine is assembled, it's time for testing. We apply a change from the torus to the regulator and measure the output voltage - it almost does not change. And it shouldn’t, since at least a small load is needed to accurately control the voltage. It could be a simple 127 (or 220 V) incandescent lamp. Now, even without any testers, you can see a change in the brightness of the lamp filament, depending on the position of the resistor-regulator engine.

So it’s clear why the second trimming resistor is indicated according to the scheme - it limits the maximum value of the current that is supplied to the pulse shaper. Without it, the output already from half of the engine reaches the maximum possible value, which makes the adjustment not smooth enough.

To correctly set the range of current changes, you need to set the main regulator to the maximum current (minimum resistance), and the tuning regulator (100 Ohms) to gradually reduce the resistance until its further decrease leads to an increase in the welding current. Capture this moment.

Now the tests themselves, so to speak, on hardware. As intended, the current is normally regulated from zero to maximum, but the output is not constant, but rather a pulsed direct current. In short, the DC electrode did not cook and still does not cook properly.

You will have to add a block of capacitors. To do this, we found 5 pieces of excellent electrolytes for 2200 uF 100 V. By connecting them with two copper strips in parallel, I got a battery like this.

We carry out tests again - the DC electrode seems to have started to cook, but a bad defect has been discovered: at the moment the electrode touches, a micro-explosion and sticking occurs - this is the capacitors being discharged. Obviously you can't do without a throttle.

And then luck did not leave us with the teacher - in the store there was simply an excellent DR-1S throttle, wound with a 2x4 mm copper busbar on the W-iron and weighing 16 kg.

It's a completely different matter! Now there is almost no sticking and the DC electrode cooks smoothly and efficiently. And at the moment of contact there is not a micro-explosion, but a kind of light hissing. In short, everyone is happy - the teacher has an excellent welding machine, and I am relieved of the headache with an archetypal object that has nothing to do with electronics :)

How to make a simple current regulator for a welding transformer

An important design feature of any welding machine is the ability to adjust the operating current. In industrial devices, different methods of current regulation are used: shunting using chokes of various types, changing the magnetic flux due to the mobility of the windings or magnetic shunting, using stores of active ballast resistances and rheostats. The disadvantages of such adjustment include the complexity of the design, the bulkiness of the resistances, their strong heating during operation, and inconvenience when switching.

The best option is to make it with taps while winding the secondary winding and, by switching the number of turns, change the current. However, this method can be used to adjust the current, but not to regulate it over a wide range. In addition, adjusting the current in the secondary circuit of a welding transformer is associated with certain problems.

Thus, significant currents pass through the control device, which leads to its bulkiness, and for the secondary circuit it is almost impossible to select such powerful standard switches that they can withstand currents up to 200 A. Another thing is the primary winding circuit, where the currents are five times less.

After a long search through trial and error, the best solution to the problem was found - a well-known thyristor controller, the circuit of which is shown in Fig. 1.

With the utmost simplicity and availability of the element base, it is easy to manage, does not require settings and has proven itself in work - it works just like a “clock”.

Power control occurs when the primary winding of the welding transformer is periodically switched off for a fixed period of time at each half-cycle of current. The average current value decreases.

The main elements of the regulator (thyristors) are connected counter and parallel to each other. They are alternately opened by current pulses generated by transistors VT1, VT2. When the regulator is connected to the network, both thyristors are closed, capacitors C1 and C2 begin to charge through the variable resistor R7. As soon as the voltage on one of the capacitors reaches the avalanche breakdown voltage of the transistor, the latter opens and the discharge current of the capacitor connected to it flows through it.

Following the transistor, the corresponding thyristor opens, which connects the load to the network. After the start of the next half-cycle of the alternating current, the thyristor closes and a new cycle of charging the capacitors begins, but in reverse polarity. Now the second transistor opens, and the second thyristor reconnects the load to the network.

By changing the resistance of the variable resistor R7, you can regulate the moment the thyristors are turned on from the beginning to the end of the half-cycle, which in turn leads to a change in the total current in the primary winding of the welding transformer T1. To increase or decrease the adjustment range, you can change the resistance of the variable resistor R7 up or down, respectively.

Transistors VT1, VT2, operating in avalanche mode, and resistors R5, R6, included in their base circuits, can be replaced with dinistors. The anodes of the dinistors should be connected to the extreme terminals of resistor R7, and the cathodes should be connected to resistors R3 and R4. If the regulator is assembled using dinistors, then it is better to use devices of the KN102A type.

Variable resistor type SP-2, the rest type MLT. Capacitors of the MBM or MBT type for an operating voltage of at least 400 V.

A correctly assembled regulator does not require adjustment. You just need to make sure that the transistors are stable in avalanche mode (or that the dinistors are switched on stably).

Attention! The device has a galvanic connection to the network. All elements, including thyristor heat sinks, must be isolated from the housing.

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Assembling homemade DC welding machines

• Welding machine: arc characteristic
• Dynamic response
• Possible details and calculations
• circuit diagram
• Welding circuit operation:
• Design of transformer and chokes
• Apparatus design
  • Parts and materials of the welding device:
  • Assembly tools

To make homemade DC welders, you will need a high-power power source that converts the rated voltage of a conventional single-phase network and provides a constant value (in amperes) of the appropriate current to directly create and maintain a normal electric arc.

Schemes of a homemade DC welding machine.

The high-power power source is a circuit consisting of the following components:

• rectifier;
• inverters;
• current and voltage transformer;
• current and voltage regulators that improve the quality characteristics of the electric arc (thyristors, triacs);
• auxiliary devices.

In fact, based on homemade circuits, the source of the electric arc was and remains a transformer, even if you do not use auxiliary components and circuits of various control units.

Homemade device: block diagram

Schematic diagram of the power supply of the welding machine.

The power supply is inserted into a corresponding box made of plastic or metal. It is supplied with the necessary elements: connecting connectors, various switches, terminals and regulators. The welding machine can be equipped with carrying handles and wheels.

Such a design of fairly good quality welding can be done independently. The main secret of such a device is a minimal understanding of the welding process, the choice of material, as well as skill and patience in the manufacture of this device.

But to assemble the device yourself, you must at least slightly understand and study the basic skills, the moment of occurrence and combustion of the electric arc and the theory of electrode melting. Know the characteristics of welding transformers and their magnetic circuits.

Back to index

Homemade device: transformer

The basis of any welding device circuit is a transformer that reduces the normal voltage (from 220 V to 45-80 V). It operates in a special arc mode with maximum power. Such transformers simply must withstand very high currents with a nominal value of about 200 A. Their characteristics must be consistent, the I-V characteristic of the transformer must certainly fully comply with special requirements, otherwise it cannot be used for arc welding mode.

Welding machines (their designs) vary greatly. The variety of homemade welding transformers is enormous, because the designs contain a lot of truly unique solutions. In addition, homemade transformers are very simple: they do not contain additional devices designed to directly regulate the current of the structure that flows:

Design of a homemade semi-automatic welding machine.

• using highly specialized regulators;
• by switching a certain number of turns of coils.

The transformer mainly consists of the following elements:

1. The magnetic core is metal. It is performed by a set of plates made of transformer steel.
2. Windings: primary (network) and secondary (working). They come with leads for adjustment (by switching) or for device circuitry.

When calculating a transformer for the required current, welding is carried out, as a rule, immediately from the working winding, without attaching circuits and various limiting and adjustment elements. The primary winding must be made with terminals and taps. They are used to increase or decrease the current (for example, to adjust the transformer at low network voltage).

The main part of any transformer is its magnetic circuit. In the manufacture of home-made designs, magnetic cores are used from decommissioned stators of electric motors, old television and power transformers. Therefore, there is a huge variety of different magnetic circuits developed by folk craftsmen for such devices.

Welding transformer based on the widely used LATR2 (a).

• magnetic circuit dimensions;
• windings – number of turns;
• input-output voltage level;
• I p – current consumed;
• I max – maximum output current.

Additional characteristics simply cannot be assessed or measured at home, even with the help of instruments. But it is precisely they that determine the suitability of the device’s transformer for forming a high-quality seam when powered in manual welding mode.

This directly depends on how the transformer “holds current” and is called the external current-voltage characteristic (IV-voltage characteristic) of the supply.

VVC – dependence of the potentials (U) on the connectors and the welding current, which varies from the load properties of the transformer and from the electric arc.

For manual welding, only a steeply falling characteristic is used, while in automatic welding machines a flat and rigid characteristic is used.

This is a fairly common question that has several solutions. There is one of the most popular ways to solve the problem; adjustment occurs through an active ballast connection at the output of the winding (secondary).

On the territory of the Russian Federation, welding for alternating current consists of a frequency of 50 Hz. A 220V network is used as a power source. And all transformers for welding have a primary and secondary winding.

In units used in an industrial area, current regulation is carried out differently. For example, using the moving functions of the windings, as well as magnetic shunting, inductive shunting of various types. Ballast resistance stores (active) and a rheostat are also used.

This choice of welding current cannot be called a convenient method, due to the complex design, overheating and discomfort when switching.

A more convenient way to regulate the welding current is to wind the secondary (secondary winding) by making taps, which will allow you to change the voltage when switching the number of turns.

But in this case, it will not be possible to control the voltage over a wide range. They also note certain disadvantages when adjusting from the secondary circuit.

Thus, the welding current regulator, at the initial speed, passes through itself a high-frequency current (HFC), which entails a cumbersome design. And standard secondary circuit switches do not require a load of 200 A. But in the primary winding circuit, the indicators are 5 times less.

As a result, an optimal and convenient tool was found in which adjusting the welding current does not seem so confusing - this is a thyristor. Experts always note its simplicity, ease of use and high reliability. The strength of the welding current depends on turning off the primary winding for specific periods of time, at each half-cycle of the voltage. At the same time, the average voltage readings will decrease.

The principle of operation of a thyristor

The regulator parts are connected both in parallel and counter to each other. They are gradually opened by current pulses, which are formed by transistors vt2 and vt1. When the device starts, both thyristors are closed, C1 and C2 are capacitors, they will be charged through resistor r7.

At the moment when the voltage of any of the capacitors reaches the avalanche breakdown voltage of the transistor, it opens, and the discharge current of the joint capacitor flows through it. After the transistor opens, the corresponding thyristor opens and connects the load to the network. Then the opposite half-cycle of the alternating voltage begins, which implies the closing of the thyristor, then a new cycle of recharging the capacitor follows, this time in the opposite polarity. Then the next transistor opens, but again connects the load to the network.

Welding with direct and alternating current

In the modern world, DC welding is used to a greater extent. This is due to the possibility of reducing the amount of filler material of the electrodes in the weld. But when welding with alternating voltage, you can achieve very high-quality welding results. Welding power sources operating with alternating voltage can be divided into several types:

1. Instruments for argon arc welding. Special electrodes are used here that do not melt, making argon welding as comfortable as possible;
2. Apparatus for the production of RDS by alternating electric current;
3. Equipment for semi-automatic welding.

Alternating welding methods are divided into two types:

• use of non-consumable electrodes;
• piece electrodes.

There are two types of DC welding, reverse and direct polarity. In the second option, the welding current moves from negative to positive, and the heat is concentrated on the workpiece. And the reverse concentrates attention on the end of the electrode.

A DC welding generator consists of a motor and a current generator itself. They are used for manual welding during installation work and in the field.

Manufacturing of the regulator

To make a control device for welding current, you will need the following components:

1. Resistors;
2. Wire (nichrome);
3. Coil;
4. design or diagram of the device;
5. Switch;
6. Spring made of steel;
7. Cable.

Operation of the ballast connection

The ballast resistance of the control apparatus is at the level of 0.001 Ohm. It is selected through experiment. Directly to obtain resistance, resistance wires of high power are mainly used; they are used in trolleybuses or on lifts.

You can even reduce the high frequency welding voltage by using a steel door spring.

Such resistance is turned on permanently or in another way, so that in the future it will be possible to easily adjust the indicators. One edge of this resistance is connected to the output of the transformer structure, the other is provided with a special clamping tool that can be thrown along the entire length of the spiral, which will allow you to select the desired voltage force.

The main part of resistors using high-power wire is produced in the form of an open spiral. It is mounted on a structure half a meter long. Thus, the spiral is also made from heating element wire. When resistors made of a magnetic alloy are combined with a spiral or any part made of steel, in the process of passing high current, it will begin to tremble noticeably. The spiral has such dependence only until the moment it stretches.

How to make a throttle yourself?

It is quite possible to make your own throttle at home. This occurs when there is a straight coil with a sufficient number of turns of the desired cord. Inside the coil are straight metal plates from the transformer. By choosing the thickness of these plates, it is possible to select the starting reactance.

Let's consider a specific example. A choke with a coil with 400 turns and a cord with a diameter of 1.5 mm is filled with plates with a cross-section of 4.5 square centimeters. The length of the coil and wire should be the same. As a result, the 120 A transformer current will be reduced by half. Such a choke is made with a resistance that can be changed. To carry out such an operation, it is necessary to measure the deepening of the passage of the core rod into the coil. Without this tool, the coil will have little resistance, but if the rod is inserted into it, the resistance will increase to the maximum.

A choke that is wound with the correct cord will not overheat, but the core may experience strong vibration. This is taken into account when screeding and fastening iron plates.

Quite a large number of industrial electric drives and technological processes use direct current for their power supply. Moreover, in such cases it is quite often necessary to change the value of this voltage. Types of transport such as the subway, trolleybuses, electric cars and other types of transport receive power from DC networks with constant voltage. But many of them need to change the voltage value supplied to the armature of the electric motor. The classic means of obtaining the required values ​​are resistive control, or the Leonardo system. But these systems are outdated, and they can be found quite rarely (especially the generator-motor system). More modern and actively being implemented now are the thyristor converter-motor and pulse converter-motor systems. Let's look at each system in more detail.

Resistor regulation

To regulate the starting current and voltage supplied to the electric motor, resistors are connected to the armature circuit in series with the armature (or the armature and the field winding in the case of a series-excited motor):

In this way, the current supplied to the electrical machine is regulated. Contactors K1, K2, K3 bypass resistors if it is necessary to change any parameter or coordinate of the electric drive. This method is still quite widespread, especially in traction electric drives, although it is accompanied by large losses in resistors and, as a consequence, rather low efficiency.

Generator-engine system

In such a system, the required voltage level is formed by changing the excitation flow of the generator:

The presence of three electric machines in such a system, large weight and dimensions and a long repair time in case of breakdowns, as well as expensive maintenance and the large inertia of such an installation made the efficiency of such a machine very low. Nowadays there are practically no generator-engine systems left; they are all being actively replaced by systems, which have a number of advantages.

Thyristor converter – motor

It received its massive development in the 60s, when thyristors began to appear. It was on their basis that the first static low-power thyristor converters were created. Such devices were connected directly to AC networks:

Voltage regulation occurs by changing. Regulation through a thyristor converter has a number of advantages over the generator-motor installation, such as high speed and efficiency, smooth regulation of DC voltage and many others.

Converter with intermediate voltage link

Everything is a little more complicated here. To obtain a constant voltage of the required value, additional auxiliary devices are used, namely an inverter, transformer, rectifier:

Here, direct current is converted into alternating current using a current inverter, then lowered or increased using a transformer (depending on the need), and then rectified again. The presence of a transformer and inverter significantly increases the cost of installation and enlarges the system, which reduces efficiency. But there is also a plus - galvanic isolation between the network and the load due to the presence of a transformer. In practice, such devices are extremely rare.

Switching DC-DC converters

These are perhaps the most modern control devices in DC circuits. It can be compared to a transformer, since the behavior of a pulse converter is similar to a transformer with a smoothly varying number of turns:

Such systems actively replace electric drives with resistive regulation, by connecting them to the machine armature in series, instead of a resistive-contactor group. I use them quite often in electric cars, and they have also gained quite a lot of popularity in underground transport (subway). Such converters emit minimal heat, which does not heat up the tunnels and can implement regenerative braking mode, which is a big plus for electric drives with frequent starting and braking.

The big advantage of such devices is that they can recuperate energy into the network, smoothly regulate the rate of current rise, and have high efficiency and speed.

You will need

• - transistors type P416, GT308;
• - variable resistor SP-2;
• - MLT resistors;
• - capacitors MBT or MBM 400 V

Instruction

Make a secondary winding when winding the welding. Change the current by switching the number of turns. This is the best option. But this method can only be used to adjust the current; it is not used to regulate it over a wide range. It is worth saying that this method is associated with certain problems. First of all, with the fact that the regulating device passes a significant current, which leads to its bulkiness, and for the secondary circuit it is impossible to select standard switches that would withstand a current of up to 200 A. The primary winding circuit is a completely different matter, since the currents here are 5 times weaker.

Assemble the thyristor regulator. The element base is accessible, it is easy to operate, does not require adjustment and has proven itself well in the process. Power adjustment is carried out by periodically turning off the first winding of the welding transformer for a specified period of time at each half-cycle of the current. In this case, the average current value decreases.

Turn on the main elements of the regulator (thyristors) in parallel and counter to each other. They will alternately open with current pulses, which are formed by transistors VT1, VT2. When power is applied to the regulator, both are closed, and capacitors C1 and C2 begin through variable R7. When one of them reaches the avalanche breakdown voltage of the transistor, the latter will open the way for the discharge current of the capacitor connected to it. After which the corresponding thyristor connects the load to the network. At the beginning of the next half-cycle, everything is repeated, but in reverse, in reverse polarity.

Adjust the torque of the thyristors by changing the resistance of the variable resistor R7 from the beginning to the end of the half-cycle. This leads to a change in the total current in the first winding of the welding transformer. To decrease or increase the adjustment range, change the resistance of the variable resistor R7 down or up, respectively.

Replace resistors R5, R6, which are included in the base circuits, and transistors VT1, VT2, which operate in avalanche mode, with dinistors. Connect the anodes of the dinistors to the extreme terminals of resistor R7, and connect the cathodes to resistors R3 and R4. To regulate the current assembled on dinistors, use devices of the KN102A type. Use transistors like P416, GT308 as VT1, VT2, but you can replace them with modern high-frequency low-power ones with similar parameters. Use a variable resistor type SP-2, type MLT. Capacitors of the MBT or MBM type with an operating voltage of 400 V or more. The regulator is not adjustable, just make sure that the transistors operate stable in avalanche mode.