Pulse arc stabilizer 01. Arc combustion stabilizers. Special functions of switching voltage stabilizers

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 chain 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. Specifications oscillators are given in the table.

Technical characteristics of oscillators

Type	Primary voltage, V	Secondary voltage idle speed, V	Consumed Power, W	Dimensional dimensions, mm	Weight, kg
M-3 OS-1 OSCN TU-2 TU-7 TU-177 OSPZ-2M	40 - 65 65 200 65; 220 65; 220 65; 220 220	2500 2500 2300 3700 1500 2500 6000	150 130 400 225 1000 400 44	350 x 240 x 290 315 x 215 x 260 390 x 270 x 310 390 x 270 x 350 390 x 270 x 350 390 x 270 x 350 250 x 170 x 110	15 15 35 20 25 20 6,5

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.

Scheme of external electrical connections 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 welding on DC. 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.

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 launched using dual control - not only due to feedback in voltage, but also in 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.

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.

The invention relates to welding production and can be used in the production or modernization of welding power sources. The purpose of the invention is to increase the power and stability of arc-igniting pulses by changing the circuit of the key cascade, which makes it possible to improve the operational properties of the stabilizer and expand the scope of its application. The pulse stabilizer of the welding arc contains two transformers 1, 2, two thyristors 7, 8, four diodes 10 13, capacitor 9, resistor 14. 1 or.

The invention relates to welding production and can be used in the production or modernization of welding power sources. The purpose of the invention is to develop a device that provides increased power and stability of arc-igniting pulses by changing the circuit of the key cascade, which makes it possible to improve the operational properties of the stabilizer and expand the scope of its application. To stabilize the process of arc welding on alternating current, at the beginning of each half-cycle of the welding voltage, a short-term powerful current pulse is applied to the arc, formed by recharging a capacitor connected to the arc power circuit using thyristor switches. In the known circuit, the capacitor cannot be recharged to the amplitude values ​​of the voltages supplying it, which reduces the power of the pulse that ignites the arc. At the same time, the power of this pulse is affected by the moment of opening of the thyristors relative to the beginning of the half-cycle of the voltage feeding the arc. This is due to the premature closing of the thyristors, since the capacitor charging current flowing through them is determined by the reactance of the capacitor. This current can keep the thyristor open as long as it exceeds the thyristor holding current. The specified condition is ensured (after the unlocking pulse arrives at the control electrode of the thyristor) for a very short time, after which the thyristor closes. The drawing shows the electrical circuit of the stabilizer. Positions 1 and 2 respectively indicate additional and welding transformers; 3 and 4 connection points to the circuits of the key thyristor cascade; 5 and 6, respectively, a welding electrode and a welded product; 7 and 8 key thyristors; 9 capacitor; 10 and 11 power diodes; 12 and 13 low-power diodes; 14 resistor. The diagram does not show the device for generating control pulses that unlock the thyristors. Control signals U y from this device are supplied to the corresponding electrodes of thyristors 7 and 8. The device operates as follows. When a positive half-wave voltage appears on the arc and thyristor 8 is turned on at the beginning of this half-cycle, capacitor 9 will instantly charge through it and diode 11. But the thyristor remains open, since until the amplitude voltage value is reached on the secondary winding of transformer 1, the current flows through the thyristor along two circuits: thyristor 8 diode 11 capacitor 9 and thyristor 8 diode 13 resistor 14. The current flowing through the first circuit is very small (not sufficient to keep the thyristor open), and through the second circuit it is sufficient to keep the thyristor open. As the voltage of a given half-cycle increases to its amplitude value, the capacitor is charged to the sum of this voltage with the voltage on the arc. Next, the voltage on the secondary winding of transformer 1 will begin to decrease and the voltage of the charged capacitor 9 will close the diode 13, which will lead to the locking of the thyristor 8 and the capacitor 9 will remain charged with the extreme value of the sum of the indicated voltages until the polarity of the voltage on the arc changes. After changing the polarity at the beginning of the next half-cycle, thyristor 7 will open with a control pulse and the capacitor will instantly recharge to the sum of the voltages acting at that moment on the secondary windings of transformers 1 and 2. Diode 12 opens, keeping thyristor 7 open until the amplitude value of the voltage on the secondary winding of transformer 1 is reached Accordingly, capacitor 9 is recharged to the sum of the amplitude value of the specified voltage and the voltage on the arc. The introduction of these elements into the electrical circuit of the stabilizer makes it possible to increase the pulse amplitude swing by two or more times and make it (swing) independent of the moment of opening of the thyristors relative to the beginning of the half-cycle of the voltage on the arc. In the above reasoning, only the amplitude value of the voltage on the secondary winding of transformer 1 is mentioned and nothing is said about the nature of the voltage change on the arc. The fact is that the electric arc has a significant stabilizing ability and during its combustion the alternating voltage on it has a rectangular shape with a flat top (meander), i.e. the voltage on the arc during the half-cycle is practically constant in amplitude (does not change in magnitude) and does not affect the nature of the charge of the capacitor 9. The use of the invention made it possible to increase the amplitude of the arc-igniting pulse by 1.8.2 times, to stabilize it when the opening moment changes over a wide range thyristors relative to the beginning of the half-cycle of the alternating voltage on the arc. By ensuring the indicated effects, it is possible to intensively destroy the oxide film during argon-arc welding of aluminum and its alloys, to stabilize the arc combustion process in a wide range of welding currents, especially in the direction of its reduction. Noted high quality formation of a weld seam.

Claim

PULSE WELDING ARC STABILIZER, including a series-connected secondary winding of a welding transformer, a circuit of back-to-back parallel connected thyristors with their control circuit, a capacitor and a secondary winding of an additional transformer, connected according to the secondary winding of the welding transformer, which is connected to the welding electrodes, characterized in that it two power and two low-power diodes and a resistor are introduced, and the power diodes are connected in series according to the thyristors, the connection point of one thyristor and the cathode of the first power diode is connected to the cathode of the first low-power diode, and the connection point of the cathode of the other thyristor and the anode of the second power diode is connected to the anode of the second low-power diode diode, anode and cathode of the first and second low-power diodes, respectively, are connected through a resistor to the capacitor plate connected to the secondary winding of an additional transformer.

1.7.4. Switching stabilizer circuit

The switching stabilizer circuit is not much more complicated than a conventional one (Fig. 1.9), but it is more difficult to configure. Therefore, for insufficiently experienced radio amateurs who do not know the rules of working with high voltage (in particular, never work alone and never adjust a switched-on device with both hands - only one!), I do not recommend repeating this scheme.

In Fig. Figure 1.9 shows the electrical circuit of a pulse voltage stabilizer for charging cell phones.

The circuit is a blocking oscillator implemented on transistor VT1 and transformer T1. Diode bridge VD1 rectifies the alternating mains voltage, resistor R1 limits the current pulse when turned on, and also serves as a fuse. Capacitor C1 is optional, but thanks to it the blocking generator operates more stably, and the heating of transistor VT1 is slightly less (than without C1).

When the power is turned on, transistor VT1 opens slightly through resistor R2, and a small current begins to flow through winding I of transformer T1. Thanks to inductive coupling, current also begins to flow through the remaining windings. At the upper (according to the diagram) terminal of winding II there is a small positive voltage, through the discharged capacitor C2 it opens the transistor even more strongly, the current in the transformer windings increases, and as a result the transistor opens completely, to a state of saturation.

After some time, the current in the windings stops increasing and begins to decrease (transistor VT1 is completely open all this time). The voltage on winding II decreases, and through capacitor C2 the voltage at the base of transistor VT1 decreases. It begins to close, the voltage amplitude in the windings decreases even more and changes polarity to negative. Then the transistor turns off completely. The voltage on its collector increases and becomes several times higher than the supply voltage (inductive surge), however, thanks to the chain R5, C5, VD4, it is limited to a safe level of 400...450 V. Thanks to the elements R5, C5, generation is not completely neutralized, and after some time the polarity of the voltage in the windings changes again (according to the principle of operation of a typical oscillating circuit). The transistor begins to open again. This continues indefinitely in a cyclical mode.

The remaining elements of the high-voltage part of the circuit assemble a voltage regulator and a unit for protecting transistor VT1 from overcurrent. Resistor R4 in the circuit under consideration acts as a current sensor. As soon as the voltage drop across it exceeds 1...1.5 V, transistor VT2 will open and close the base of transistor VT1 to the common wire (forcefully close it). Capacitor C3 speeds up the reaction of VT2. Diode VD3 is necessary for normal operation voltage stabilizer.

The voltage stabilizer is assembled on one chip - an adjustable zener diode DA1.

To galvanically isolate the output voltage from the mains voltage, optocoupler VO1 is used. The operating voltage for the transistor part of the optocoupler is taken from winding II of transformer T1 and smoothed by capacitor C4. As soon as the voltage at the output of the device becomes greater than the nominal one, current will begin to flow through the zener diode DA1, the optocoupler LED will light up, the collector-emitter resistance of the phototransistor VO 1.2 will decrease, the transistor VT2 will open slightly and reduce the voltage amplitude at the base of VT1. It will open weaker, and the voltage on the transformer windings will decrease. If the output voltage, on the contrary, becomes less than the nominal voltage, then the phototransistor will be completely closed and the transistor VT1 will “swing” at full strength. To protect the zener diode and LED from current overloads, it is advisable to connect a resistor with a resistance of 100...330 Ohms in series with them.

Setting up

First stage: It is recommended to connect the device to the network for the first time using a 25 W, 220 V lamp, and without capacitor C1. The resistor R6 slider is set to the bottom (according to the diagram) position. The device is turned on and off immediately, after which the voltages on capacitors C4 and C6 are measured as quickly as possible. If there is a small voltage across them (according to the polarity!), then the generator has started, if not, the generator does not work, you need to look for errors on the board and installation. In addition, it is advisable to check transistor VT1 and resistors R1, R4.

If everything is correct and there are no errors, but the generator does not start, swap the terminals of winding II (or I, but not both at once!) and check the functionality again.

Second phase: turn on the device and control with your finger (not the metal pad for the heat sink) the heating of transistor VT1, it should not heat up, the 25 W light bulb should not light up (the voltage drop across it should not exceed a couple of volts).

Connect some small low-voltage lamp to the output of the device, for example, rated for a voltage of 13.5 V. If it does not light, swap the terminals of winding III.

And at the very end, if everything works fine, check the functionality of the voltage regulator by rotating the slider of the trimming resistor R6. After this, you can solder in capacitor C1 and turn on the device without a current-limiting lamp.

The minimum output voltage is about 3 V (the minimum voltage drop at the DA1 pins exceeds 1.25 V, at the LED pins - 1.5 V).

If you need a lower voltage, replace the zener diode DA1 with a resistor with a resistance of 100...680 Ohms. The next setup step requires setting the device output voltage to 3.9...4.0 V (for a lithium battery). This device charges the battery with an exponentially decreasing current (from approximately 0.5 A at the beginning of the charge to zero at the end (for a lithium battery with a capacity of about 1 A/h this is acceptable)). In a couple of hours of charging mode, the battery gains up to 80% of its capacity.

About details

A special design element is a transformer.

The transformer in this circuit can only be used with a split ferrite core. The operating frequency of the converter is quite high, so only ferrite is needed for transformer iron. And the converter itself is single-cycle, with constant magnetization, so the core must be split, with a dielectric gap (one or two layers of thin transformer paper are laid between its halves).

It is best to take a transformer from an unnecessary or faulty similar device. In extreme cases, you can wind it yourself: core cross-section 3...5 mm 2, winding I - 450 turns with a wire with a diameter of 0.1 mm, winding II - 20 turns with the same wire, winding III - 15 turns with a wire with a diameter of 0.6...0, 8 mm (for output voltage 4…5 V). When winding, strict adherence to the winding direction is required, otherwise the device will work poorly or not work at all (you will have to make efforts when setting it up - see above). The beginning of each winding (in the diagram) is at the top.

Transistor VT1 - any power of 1 W or more, collector current of at least 0.1 A, voltage of at least 400 V. Current gain b 2 1 e must be greater than 30. Transistors MJE13003, KSE13003 and all other types 13003 of any type are ideal companies. As a last resort, domestic transistors KT940, KT969 are used. Unfortunately, these transistors are designed for a maximum voltage of 300 V, and at the slightest increase in the mains voltage above 220 V they will break through. In addition, they are afraid of overheating, i.e. they need to be installed on a heat sink. For transistors KSE13003 and MJE13003, a heat sink is not needed (in most cases, the pinout is the same as that of domestic KT817 transistors).

Transistor VT2 can be any low-power silicon, the voltage on it should not exceed 3 V; the same applies to diodes VD2, VD3. Capacitor C5 and diode VD4 must be designed for a voltage of 400...600 V, diode VD5 must be designed for the maximum load current. The diode bridge VD1 must be designed for a current of 1 A, although the current consumed by the circuit does not exceed hundreds of milliamps - because when turned on, a rather powerful surge of current occurs, and you cannot increase the resistance of resistor Y1 to limit the amplitude of this surge - it will heat up very much.

Instead of the VD1 bridge, you can install 4 diodes of type 1N4004...4007 or KD221 with any letter index. Stabilizer DA1 and resistor R6 can be replaced with a zener diode, the voltage at the output of the circuit will be 1.5 V greater than the stabilization voltage of the zener diode.

The “common” wire is shown in the diagram for graphical purposes only and should not be grounded and/or connected to the device chassis. The high voltage part of the device must be well insulated.

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