RU2032506C1 - Welding device - Google Patents

Abstract

FIELD: welding. SUBSTANCE: welding device has a welding transformer, antiparallel thyristors in the circuit of its primary winding and the thyristor control circuit. The cross-section of the magnetic circuit and the number of turns of the primary winding of the welding transformer are designed for the part of the mains voltage equal to the geometric difference of the voltage vectors- the mains voltage minus half-difference of the mains voltage and reduced to the number of turns of the primary winding of the voltage on the arc space. An extra capacitor ensuring the pulse operation of the idle stroke is switched on parallel to the secondary winding of the welding transformer. EFFECT: facilitated manufacture. 4 dwg

Description

 The invention relates to welding.

 Closest to the proposed device is a welding device consisting of a welding transformer, the cross section of the magnetic circuit and the number of turns of the primary winding of which are designed for full mains voltage, antiparallel thyristors in the primary winding circuit of the welding transformer and thyristor control circuit.

 The disadvantages of the device: increased weight and cost; large losses when working in idle mode.

 The high mass and cost of the device are due to the fact that the cross section of the magnetic circuit of the welding transformer and the number of turns of its primary winding are designed for full mains voltage. Losses of idling are large, since a voltage close to the full voltage of the supply network is applied to the welding transformer.

 The aim of the invention is to reduce the mass and cost of the device for welding by reducing the cross section of the magnetic circuit of the welding transformer, reducing idle losses by reducing the voltage supplied to the welding transformer in idle mode.

 This goal is achieved by the fact that the welding device consists of a welding transformer, the cross section of the magnetic circuit and the number of turns of the primary winding of which are designed for a part of the mains voltage equal to the geometric difference of the voltage vectors to the mains voltage minus the half-difference of the mains voltage and the number of turns of the primary winding of the voltage across the arc gap antiparallel thyristors in the primary circuit of the welding transformer, thyristor control circuit and additional capacitor, Turning parallel with the secondary winding of the welding transformer.

 When the inventive device is operating under load (with a lighted arc), not all mains voltage is used to create the main magnetic flux. Part of the mains voltage is balanced by the voltage drop across the inductance of the primary winding of the welding transformer. Therefore, with an equal number of turns of the windings, the cross section of the magnetic circuit of the welding transformer of the claimed device is less than that of the prototype, since it is designed only for part of the mains voltage. Due to this, the inventive device has less than the prototype, mass and cost.

 The cross section of the magnetic circuit and the number of turns of the primary winding of the welding transformer should be designed for the most difficult welding mode for the welding transformer with fully open thyristors. In this case, the voltage drop across the inductance of the primary winding of the welding transformer is equal to half the geometric difference of the mains voltage vectors and the number of turns of the primary voltage winding in the arc gap. Half as the total voltage drop across the inductance of the welding transformer is divided equally between the windings, reduced to the number of turns of the primary winding. The need to consider the voltage across the arc gap is active, and the voltage drop across the leakage inductance of the welding flux of the welding transformer is inductive. Thus, the cross section of the magnetic circuit and the number of turns of the primary winding of the welding transformer are calculated for the part of the mains voltage equal to the geometric difference of the voltage vectors to the mains voltage minus the half-difference of the mains voltage and the number of turns of the primary winding of the voltage across the arc gap.

 In idle mode, despite the cross section of the welding transformer magnetic circuit reduced in comparison with the prototype, the magnetic circuit does not saturate due to the introduction of an additional capacitor connected to the secondary winding of the welding transformer into the inventive device. After opening the thyristors, an additional capacitor charges. Due to the inductance of the magnetic flux of the welding transformer, the voltage across the capacitor, reduced to the number of turns of the primary winding, briefly exceeds the mains voltage. (As you know, when you turn on the L-C circuit under voltage, the voltage on the capacitance can shortly reach the double instantaneous value of the mains voltage). During this period of time, a negative voltage will be applied to the thyristors and they will be locked. The output voltage of the device for welding in idle mode due to this will be in the form of short-term bipolar pulses one at a half-period of the mains voltage.

 The specified idle mode of the claimed device will allow, firstly, to exclude saturation of the magnetic circuit, despite the fact that the cross section of the magnetic circuit is designed only for part of the mains voltage and, secondly, to reduce the loss of idling by reducing the voltage supplied to the welding transformer.

напряжение питающей сети;

напряжение на дуговом промежутке, приведенное к числу витков первичной обмотки;

ток нагрузки); на фиг. 3 векторная диаграмма работы сварочного трансформатора под нагрузкой; на фиг. 4 кривые напряжения питающей U_сети (ωt) и напряжения на дуговом промежутке U $\genfrac{}{}{0ex}{}{\text{'}}{\text{д}}$ _.хх ( ωt), приведенного к числу витков первичной обмотки, в режиме холостого хода. Устройство для сварки состоит из сварочного трансформатора 1, сечение магнитопровода и число витков первичной обмотки которого рассчитаны на часть сетевого напряжения, равную геометрической разнице напряжений сетевому напряжению минус полуразницу сетевого напряжения и приведенного к числу витков первичной обмотки напряжения на дуговом промежутке, антипараллельных тиристоров 2, включенных в цепь первичной обмотки сварочного трансформатора, схемы 3 управления тиристорами и дополнительного конденсатора 4, подключенного параллельно вторичной обмотке сварочного трансформатора.In FIG. 1 shows the electrical circuit of the proposed device; in FIG. 2 equivalent circuit of a welding transformer, reduced to the number of turns of the primary winding, when working under load (the diagram shows the voltages and currents expressed in vector form:

mains voltage;

voltage on the arc gap, reduced to the number of turns of the primary winding;

load current); in FIG. 3 vector diagram of the welding transformer under load; in FIG. 4 voltage curves of the supply _network U (ωt) and voltage across the arc gap U $\genfrac{}{}{0ex}{}{\text{''}}{\text{d}}$ _.xx (ωt), reduced to the number of turns of the primary winding, in idle mode. The welding device consists of a welding transformer 1, the cross section of the magnetic circuit and the number of turns of the primary winding of which are calculated for the part of the mains voltage equal to the geometric difference in voltage of the mains voltage minus the half-difference of the mains voltage and reduced to the number of turns of the primary winding of the voltage across the arc gap, antiparallel thyristors 2 included in the primary winding circuit of a welding transformer, thyristor control circuit 3 and an additional capacitor 4 connected in parallel to the original winding of the welding transformer.

делится дуговое напряжение

, приведенное к числу витков первичной обмотки, падение напряжения на индуктивности первичной обмотки

и падение напряжения на индуктивности вторичной обмотки

приведенное к числу витков первичной обмотки. При этом на создание основного магнитного потока (паралельная ветвь схемы замещения) используется на все напряжения сети

, а только часть его, без падения напряжения на индуктивности рассеяния магнитного потока первичной обмотки сварочного трансформатора, т.е.

-

. Следовательно, сечение магнитопровода при работе под нагрузкой может быть меньшим, чем у прототипа, рассчитанным не на сетевое напряжение, а на его часть. Сечение и количество витков обмоток трансформатора при этом такие же, как у прототипа.It is convenient to consider the operation of the device under load according to the equivalent circuit of the welding transformer, reduced to the number of turns of the primary winding operating under load (Fig. 2). The equivalent circuit shows the voltage drop across the circuit elements, expressed in vector form. It is seen that the supply voltage

arc voltage divided

reduced to the number of turns of the primary winding, the voltage drop across the inductance of the primary winding

and voltage drop across the secondary inductance

reduced to the number of turns of the primary winding. At the same time, all mains voltages are used to create the main magnetic flux (parallel branch of the equivalent circuit)

, but only part of it, without a voltage drop on the inductance of the scattering of the magnetic flux of the primary winding of the welding transformer, i.e.

-

. Therefore, the cross section of the magnetic circuit when working under load can be less than that of the prototype, designed not for the mains voltage, but for its part. The cross section and the number of turns of the transformer windings are the same as those of the prototype.

 In FIG. 2, the most severe mode of operation of the transformer with the full opening of the thyristors in the circuit of its primary winding is considered.

 Smaller conductivity angles of the thyristors correspond to a lighter mode of operation of the transformer and its magnetic circuit will not be saturated.

совпадает по фазе с током

, а падение напряжения на индуктивности сварочного трансформатора

-

опережает по фазе ток

на

.In FIG. 3 is a vectorial stress diagram of FIG. 2. The need to represent stresses in vector form is due to the fact that the voltage drop across the arc gap

coincides in phase with the current

, and the voltage drop across the inductance of the welding transformer

-

phase ahead current

on the

.

 When switching to idle mode and applying to the primary winding of the entire mains voltage, the magnetic circuit, designed only for part of the mains voltage, should be saturated and bring the device into an inoperative state. To avoid this, when switching to idle mode, it is necessary to reduce the voltage supplied to the primary winding of the welding transformer with high speed. This is ensured by introducing an additional capacitor 4 of FIG. 1.

The operation of the device in idle mode is illustrated in FIG. 4. There are curves of the mains voltage U of the _network (ωt) and the voltage across the arc gap U $\genfrac{}{}{0ex}{}{\text{''}}{\text{d}}$ _.xx (ωt), reduced to the number of turns of the primary winding, in idle mode. When the thyristors 2 of FIG. 1, the additional capacitor 4 of FIG. 1. The voltage across the capacitor, reduced to the number of turns of the primary winding and equal to the voltage across the arc gap U _d.xx (ωt) of FIG. 4, briefly exceed the instantaneous value of the mains voltage U of the _network (ωt). The time period during which U ^' _d.xx > U of the _network in FIG. 4 denotes α. The capacity of the additional capacitor 4 of FIG. 1 is selected so that α exceeds the time required for locking the thyristors. During the time α while a negative voltage is applied to the thyristors, the thyristors will be blocked. After that, the voltage at the additional capacitor 4 of FIG. 1 is discharged through the secondary winding of a welding transformer. The voltage at the device output has the form of a curve U _d.xx (ωt) in FIG. 4. These are short-term bipolar pulses one at a half-period of the mains voltage. The shape of the voltage supplied to the primary winding of the welding transformer is close to the shape of the output voltage U _d.xx (ωt), i.e. voltage supplied to the welding transformer has decreased significantly. This eliminates the saturation of the magnetic circuit and reduces the loss of idling.

After ignition of the arc, the voltage at the additional capacitor 4 of FIG. 1, equal to U ^' _d.xx , decreases sharply and the thyristors are not _blocked . The device goes into welding mode. If ignition has not occurred, the thyristors will be locked for a period of time α. A rupture of an already burning arc will also lead to a quick shutdown of the thyristors and prevent saturation of the welding transformer magnetic circuit.

As transformer 1 (Fig. 1), the TMD 401 transformer was used, the cross section of the magnetic circuit of which was reduced from 64 to 38.4 cm ² , i.e. 40% Antiparallel thyristors 2 (Fig. 1) had a T 142-80 grade. As a control circuit for thyristors 3 (Fig. 1), a known circuit was used. Additional capacitor 4 (Fig. 1) type MBGCH-1 4 microfarads 500 V.

·100%

40% Благодаря этому заявляемое устройство легче и дешевле прототипа.When the open circuit voltage of 80 V and the voltage at the arc gap of 30 V, the cross section of the magnetic circuit of the welding transformer in the inventive device is less than that of the prototype

·100%

40% Thanks to this, the inventive device is lighter and cheaper than the prototype.

 Loss of idling is 5-15 watts, instead of 60-130 watts of the prototype.

Claims (1)

 A DEVICE FOR WELDING, comprising a welding transformer, counter-parallel thyristors in the circuit of its primary winding and a thyristor control circuit, characterized in that, in order to reduce the mass and cost of the device by reducing the cross section of the magnetic circuit of the welding transformer, reducing open-circuit losses by reducing voltage, supplied to the welding transformer in idle, it is equipped with a capacitor connected in parallel with the secondary winding of the welding transformer.

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