Transformer with pulse stabilizer. Oscillators and pulsed arc exciters Special functions of pulsed voltage stabilizers

3.5.3. Expanded acoustic sensor circuit The gain of weak signals from microphone VM1 is adjusted using a variable resistor R6 (see Fig. 3.9). The lower the resistance of this resistor, the greater the gain of the transistor stage on transistor VT1. At

4.4.2. Timer electrical circuit When the EMT is connected to a 220 V network, voltage is supplied to coil K1 (having a resistance of 3.9 kOhm) through limiting resistor R1. Using a system of gears and voltage applied to this coil (using electromagnetic induction)

2.3. Block diagram The block diagram of a switching power supply for a personal computer of the ATX design is shown in Fig. 2.1. Rice. 2.1. Block diagram of a switching power supply from DTK of the ATX design. Input alternating voltage 220 V, 50 Hz is supplied to the input

2.4. Circuit diagram The complete circuit diagram of a transformerless power supply with a maximum secondary power of 200 W from DTK is shown in Fig. 2.2. Rice. 2.2. Schematic diagram of a 200 W transformerless power supply from DTK All elements on

3.3. Block diagram The block diagram of a switching power supply for AT/XT type computers, containing a typical set of functional units, is shown in Fig. 3.1. Modifications of power supplies may have differences only in the circuitry implementation of the nodes while preserving

3.4. Schematic diagram Switching power supplies of this class have several different modifications of the circuitry implementation of individual auxiliary units. There are no fundamental differences in their operating characteristics, and the diversity is explained by many

Diagram, device operation The gas distribution mechanism includes: a camshaft and its drive. Transmission parts - pushers with guide bushings, and with overhead valves there are also rods and rocker arms, valves, their guide bushings and springs, support

General diagram of electrical equipment Electrical equipment of cars is a complex system of interconnected electrical alarms, ignition, fuses, instrumentation, and connecting wires. Rice.

2.6. Sensitive video amplifier circuit Those who are involved in the use of video monitoring circuits in a limited area will find this material useful. Regarding possible options for providing security in confined spaces, I would like to note once again that it is not always cost-effective

Oscillator- this is a device that converts low voltage industrial frequency current into high frequency current (150-500 thousand Hz) and high voltage (2000-6000 V), the application of which to the welding circuit facilitates excitation and stabilizes the arc during welding.

The main application of oscillators is in argon-arc welding with alternating current with a non-consumable electrode of thin metals and in welding with electrodes with low ionizing properties of the coating. The electrical circuit diagram of the OSPZ-2M oscillator is shown in Fig. 1.

The oscillator consists of an oscillating circuit (capacitor C5, the movable winding of the high-frequency transformer and spark gap P are used as an induction coil) and two inductive choke coils Dr1 and Dr2, a step-up transformer PT, and a high-frequency transformer high-frequency transformer.

The oscillatory circuit generates a high-frequency current and is connected to the welding circuit inductively through a high-frequency transformer, the terminals of the secondary windings of which are connected: one to the grounded terminal of the output panel, the other through capacitor C6 and fuse Pr2 to the second terminal. To protect the welder from electric shock, a capacitor C6 is included in the circuit, the resistance of which prevents the passage of high voltage and low frequency current into the welding circuit. In case of breakdown of capacitor C6, fuse Pr2 is included in the circuit. The OSPZ-2M oscillator is designed for connection directly to a two-phase or single-phase network with a voltage of 220 V.

Rice. 1. : ST - welding transformer, Pr1, Pr2 - fuses, Dr1, Dr2 - chokes, C1 - C6 - capacitors, PT - step-up transformer, VChT - high-frequency transformer, R - arrester	Rice. 2. : Tr1 - welding transformer, Dr - choke, Tr2 - step-up oscillator transformer, P - spark gap, C1 - circuit capacitor, C2 - circuit protective capacitor, L1 - self-induction coil, L2 - communication coil

During normal operation, the oscillator crackles evenly, and due to the high voltage, a breakdown of the spark gap occurs. The spark gap should be 1.5-2 mm, which is adjusted by compressing the electrodes with an adjusting screw. The voltage on the elements of the oscillator circuit reaches several thousand volts, so regulation must be performed with the oscillator turned off.

The oscillator must be registered with the local telecommunications inspection authorities; during operation, ensure that it is correctly connected to the power and welding circuit, as well as that the contacts are in good condition; work with the casing on; remove the casing only during inspection or repair and when the network is disconnected; monitor the good condition of the working surfaces of the spark gap, and if carbon deposits appear, clean them with sandpaper. It is not recommended to connect oscillators with a primary voltage of 65 V to the secondary terminals of welding transformers such as TS, STN, TSD, STAN, since in this case the voltage in the circuit decreases during welding. To power the oscillator, you need to use a power transformer with a secondary voltage of 65-70 V.

The connection diagram of oscillators M-3 and OS-1 to a welding transformer of the STE type is shown in Fig. 2. Technical characteristics of the oscillators are given in the table.

Technical characteristics of oscillators

Pulse arc exciters

These are devices that serve to supply synchronized pulses of increased voltage to the AC welding arc at the moment of polarity change. Thanks to this, re-ignition of the arc is greatly facilitated, which allows reducing the no-load voltage of the transformer to 40-50 V.

Pulse exciters are used only for arc welding in a shielded gas environment with a non-consumable electrode. The exciters on the high side are connected in parallel to the transformer power supply (380 V), and on the output - parallel to the arc.

Powerful series exciters are used for submerged arc welding.

Pulse arc exciters are more stable in operation than oscillators; they do not create radio interference, but due to insufficient voltage (200-300 V) they do not ensure ignition of the arc without contact of the electrode with the product. There are also possible cases of combined use of an oscillator for the initial ignition of the arc and a pulse exciter to maintain its subsequent stable combustion.

Welding arc stabilizer

To increase the productivity of manual arc welding and economical use of electricity, the welding arc stabilizer SD-2 was created. The stabilizer maintains a stable burning of the welding arc when welding with alternating current with a consumable electrode by applying a voltage pulse to the arc at the beginning of each period.

The stabilizer expands the technological capabilities of the welding transformer and allows you to perform alternating current welding with UONI electrodes, manual arc welding with a non-consumable electrode of products made of alloy steels and aluminum alloys.

The diagram of external electrical connections of the stabilizer is shown in Fig. 3, a, oscillogram of the stabilizing pulse - in Fig. 3, b.

Welding using a stabilizer makes it possible to use electricity more economically, expand the technological capabilities of using a welding transformer, reduce operating costs, and eliminate magnetic blast.

Welding device "Discharge-250". This device is developed on the basis of a TSM-250 welding transformer and a welding arc stabilizer that produces pulses with a frequency of 100 Hz.

The functional diagram of the welding device and the oscillogram of the open circuit voltage at the device output are shown in Fig. 4, a, b.

Rice. 3. : a - diagram: 1 - stabilizer, 2 - cooking transformer, 3 - electrode, 4 - product; b - oscillogram: 1 - stabilizing pulse, 2 - voltage on the secondary winding of the transformer	Rice. 4. a - device diagram; b - oscillogram of open circuit voltage at the device output

The “Discharge-250” device is intended for manual arc welding with alternating current using consumable electrodes of any type, including those intended for direct current welding. The device can be used when welding with non-consumable electrodes, for example, when welding aluminum.

Stable burning of the arc is ensured by supplying the arc at the beginning of each half of the alternating voltage period of the welding transformer with a voltage pulse of direct polarity, i.e., coinciding with the polarity of the specified voltage.

An arc stabilizer is a necessary element of equipment for arc welding with a non-consumable electrode using alternating current at industrial frequency. Its task is to ensure re-excitation of the arc when the polarity changes from direct to reverse. The stabilizer must generate pulses of sufficient energy and duration to ensure re-excitation of the arc. Typically, the amplitude of the stabilizer voltage pulse reaches 400-600V.

Stabilizers are called active, in which the pulse energy is accumulated in some kind of storage device (inductive or capacitive) and is introduced into the arc circuit at the command of the control device. In passive stabilizers, the pulse is generated due to processes occurring in the arc circuit. Only active type stabilizers have gained practical distribution.

The most important part of the stabilizer is the control circuit for the moment of pulse generation. The stabilizer pulse must be generated after changing the polarity of the arc voltage with a certain delay determined by the development time of the glow discharge. There are two possible ways to generate a pulse: potential and differential. In the first case, the pulse is generated when the arc voltage reaches a certain level, in the second - when the arc voltage changes sharply. If the delay of the circuit is small, no more than 1-2 μs, it is advisable to use the potential method. It allows you to select an impulse when it is needed, i.e. when an anomalous glow discharge is formed. If the delay is significant, the input signal of the control circuit must be allocated at the initial stage of the voltage recovery process. Here it is advisable to use differential circuits.

Stabilizers are part of AC welding units and are not available separately. In Fig. Figure 5.7 shows a schematic diagram of an arc combustion stabilizer.

Rice. 5.7. Schematic diagram of an arc stabilizer.

Capacitor C is charged from the step-up transformer 3T through diode D. At the right moment, when the supply voltage (welding transformer CT) changes from direct polarity to reverse, a current pulse is supplied to the control electrode of thyristor T. The thyristor is unlocked and capacitor C is discharged into the arc gap. A short but powerful current pulse occurs and the arc is well excited when the welding current passes through zero.

Welding cycle

The welding cycle block provides:

Turning on the cycle at the operator’s command;

Switching on the supply of protective gas;

A ban on turning on the welding current until the gas enters the welding zone and displaces the air present there;

Turning on the arc ignition device;

Increase in current to operating current;

Disabling the arc ignition device;

Turning on the movement of the welding torch and the supply of filler wire;

At the operator’s command, reduce the welding current for a time set by the operator;

Switching off the welding power source;

turning off the gas supply for a specified time and returning the circuit to its original state.

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To maintain a stable arc during manual arc welding with consumable electrodes, a pulse welding arc stabilizer type SD-3 is used in conjunction with commercially produced transformers.
When installing automation systems, the stabilizer can be used for manual argon arc welding of pipe lines and metal structures made of aluminum and its alloys with a non-consumable electrode, as well as for manual arc welding of steel pipe lines and metal structures with consumable electrodes. In the latter case, you can use electrodes designed for welding with alternating current (type MP-3) and direct current (type UONI-13/45).
The operation of the stabilizer is based on maintaining a stable burning of the arc by applying voltage pulses of reverse polarity to it at the beginning of each half-cycle. The principle of stabilizing the welding arc is as follows. When welding with alternating current, the welding arc breaks when the welding current passes through zero. Thus, at a mains frequency of 50 Hz, the arc goes out and is re-ignited at twice the mains frequency. Re-ignition of the arc occurs from a “spike” of the no-load voltage of the welding transformer, the value of which can reach 90-100 V. However, this voltage is not enough for re-ignition and stable burning of the arc. To reliably ignite the arc, at the beginning of each half-wave, the stabilizer supplies voltage pulses to the secondary winding, the amplitude value of which reaches 200 V. These pulses contribute to stable burning of the arc. The polarity of the stabilizing pulses is reversed, i.e., when a positive half-wave increases between the electrode and the workpiece, a pulse is sent from the welding transformer into the arc gap, the leading edge of which has a negative polarity.
Structurally, the arc stabilizer is an attachment that can be installed directly on the welding transformer. Before connecting it, the welding transformer must be disconnected from the network. After power is supplied to the welding transformer and the electrode briefly touches the product, the stabilizer should turn on, as indicated by the light on its front panel. If this does not happen, you need to swap the power cables from the network. If the stabilizer and welding transformer are working properly, the arc stabilizer works only during welding and turns off no later than 1 second after welding stops. One of the signs of the stabilizer’s operation is a change in the characteristic sound of a welding transformer. This sound is most audible after stopping welding for 1 second.
The welding arc stabilizer SD-3 is powered from an alternating current network with a voltage of 380 V and a frequency of 50 Hz. Permissible voltage deviation from nominal +10 and -15%. Power consumption no more than 50 V-A. Reading 1 s.
When argon arc welding of aluminum and its alloys with non-consumable electrodes, the arc stabilizer can work in conjunction with welding transformers; having an open circuit voltage of 80 V and a current of 50 to 800 A. For manual arc welding with consumable electrodes, the stabilizer can be used with transformers having an open circuit voltage of 45-80 V and a current of 80 to 300 A. The SD-3 stabilizer has dimensions of 334* 208x152 mm and weight 7 kg.

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A pulsed arc stabilizer (ISGD) is a generator of high-voltage peak pulses supplied to the arc at the moment the current passes through zero. This ensures reliable re-ignition of the arc, which guarantees high stability of the AC arc.

Let's consider the circuit of the SD-3 stabilizer (Figure 5.31). Its main parts are power transformer G, switching capacitor WITH and thyristor switch VS 1, VS 2 with control system A. The stabilizer feeds the arc parallel to the main source G- welding transformer. First, let's analyze its operation when the welding transformer is idling. At the beginning of the half-cycle, the thyristor opens VS 1, as a result, a current pulse will pass through the circuit shown by the thin line. At the same time, according to the current EMF of the transformer T source G create a charge on the capacitor with the polarity indicated in the figure. The capacitor charge current increases until the voltage across it is equal to the total voltage of the transformer G and the source G. After this, the current begins to decrease, which will cause self-induction to appear in the EMF circuit, tending to keep the current unchanged. Therefore, the capacitor charge WITH will continue until the voltage across the capacitor reaches double the supply voltage. Capacitor charge voltage applied to VS 1 in the opposite direction, the thyristor will close. In the second half-cycle the thyristor opens VS 2, and the pulse current will go in the opposite direction. In this case, the impulse will be more powerful, since it is caused by the consonant action of the EMF of the transformers T And G, as well as the capacitor charge WITH. As a result, the capacitor will be recharged to an even higher level. This resonant nature of the recharge makes it possible to obtain stabilizing voltage pulses with an amplitude of about 200 V at the interelectrode gap at a relatively low voltage of the power transformer of about 40 V (Figure 5.31, b). Pulse generation frequency - 100 Hz. Voltage from the main source is also supplied to the interelectrode gap (Figure 5.31, d). When indicated in the figure. 5.31, aphasing of transformers T And G The polarities of the voltages supplied to the interelectrode gap from the main source (shown by the dotted line) and from the stabilizer (thin line) are opposite. This inclusion of the stabilizer is called counter. To the drawing. 5.31, c shows the voltage at the interelectrode gap under the combined action of the stabilizer and the main source.

Drawing. 5.31 – Pulse arc stabilizer

If you change the phasing of the main transformer G or stabilizer, then the polarity of the voltages on the arc from the main source and from the stabilizer will coincide (Figure 5.31, a). This connection is called a consonant, and is used in the design of other stabilizers. Re-ignition occurs at the moment a stabilizing pulse is applied; usually the ignition time does not exceed 0.1 ms.

When switched on oppositely, a stabilizing pulse, although it does not coincide in direction with the transformer voltage G, also promotes re-ignition (see Figure 5.31, c). At the same time on the drawing. 5.31, and it is clear that part of the pulse current passing through the secondary winding G(thin line), coincides with the own current of this winding (dashed line) and therefore does not prevent the rapid increase in its current to the value necessary for re-ignition.

The SD-3 stabilizer can be used both for manual welding with a covered electrode and for welding aluminum with a non-consumable electrode. The control system starts the stabilizer only after the arc is ignited. After the arc breaks, it works for no more than 1 second, which increases work safety.

The described autonomous stabilizer can be used in conjunction with any transformer for manual welding with an open circuit voltage of at least 60 V, while the stability of the arc increases so much that it becomes possible to weld with alternating current using electrodes with calcium fluoride coating, whose stabilizing properties are considered low.

It is more effective to use stabilizers built into the source housing. Transformers Razryad-160, Razryad-250 and TDK-315 are produced with built-in stabilizers; they have a reactive winding of three sections. The range switch, which first provides consonant and then counter connection of the reactive winding with the primary, allows you to increase the current in seven steps. Thanks to the use of a pulse stabilizer, it became possible to reduce the no-load voltage of transformers to 45 V. And this, in turn, sharply reduced the current consumed from the network and the weight of the transformers. Unlike stand-alone ones, the built-in stabilizer is triggered using dual control - not only due to voltage feedback, but also current. This increases the reliability of its operation, in particular, it prevents false alarms due to short circuits by drops of electrode metal. Transformers TDM-402 with moving windings and TDM-201 with a magnetic shunt are produced with a built-in stabilizer.