RU2248865C2 - Power source for electric arc welding - Google Patents

Abstract

FIELD: electric welding AC apparatuses with intermittent power supply of electric arc.

SUBSTANCE: primary winding of welding transformer is connected in series with thyristors connected in parallel and mutually opposite and provided with control unit. Circuit of connected in series capacitor and inductor is connected in parallel with said thyristors. Inductor is magnetically coupled with additional winding connected to secondary winding of welding transformer. Inductor and its additional winding are in the form of separate transformer in which inductor is primary winding and additional winding is secondary one. Throttle is connected in series with primary winding of welding transformer. One of additional capacitors is connected in parallel with thyristors and with primary winding of transformer. Secondary winding of separate transformer and connected in series with it other additional capacitor are connected in parallel with secondary winding of welding transformer. Electric current pickup is connected in series with circuit of secondary winding of welding transformer. Outlet of said pickup is connected with control unit of thyristors.

EFFECT: enhanced operational characteristics of power source.

1 dwg

Description

The invention relates to the field of arc welding, in particular to electric welding machines of alternating current with intermittent arc supply.

A known source of power for arc welding, containing a transformer with a primary winding connected through counter-parallel connected thyristors to the terminals of the connection to a single-phase AC network, and a secondary winding, which is the output of the device, the transformer is equipped with an additional winding located on the common for all windings of the magnetic circuit and connected through a capacitor parallel to the primary winding of the transformer (AS No. 925571, BI No. 17, 1982). The disadvantages of this power source for arc welding include: a high level of high-frequency interference created by the operation of the thyristor controller; in connection with the natural CVC, an increased value of the input current and, accordingly, low cos.

A known power source for arc welding according to the patent of the Russian Federation No. 2066606, MKI (6) 23 K 9/067, 9/095, published in BI No. 26, 1996 (prototype). The power source adopted for the prototype contains a transformer with a primary winding, in series with which counter-parallel connected thyristors are connected, in parallel with which a capacitor and an inductor are connected in series, and a secondary winding of the transformer, into which an additional winding is magnetically connected to the inductor.

The prototype diagram does not show technological resistances, one of which is connected in series with the primary winding of the transformer and serves to limit the input current of the power source and create a sloping I-V characteristic, which degrades cos, and the second is connected in parallel to the secondary winding of the transformer and serves to close the high-frequency circuit of ignition pulses, but since it is connected in parallel with the secondary winding, heat loss additionally occurs on it.

The disadvantages of the prototype are the presence of large heat losses at the indicated resistances, the significant dimensions and weight of the power source for arc welding, a high level of high-frequency interference, low cosφ and, accordingly, a higher power consumption.

The objective of the invention is to improve the operational characteristics of the power source for arc welding.

The problem is solved in that the power source for arc welding, containing a welding transformer, with a primary winding of which thyristors are connected in parallel and connected in parallel with the control unit, and in parallel with the thyristors is connected a chain of series-connected capacitor and inductance coil magnetically connected with an additional winding included in the secondary winding of the welding transformer, equipped with a choke, two capacitors and a current sensor, and the inductor and its The additional winding is made in the form of a separate transformer, in which the inductor is the primary winding, and the additional winding is the secondary winding, while the inductor is connected in series to the primary winding of the welding transformer, one of the introduced capacitors is parallel to the thyristors and primary winding of the welding transformer, the secondary winding of a separate transformer and another connected capacitor connected in series to it is connected in parallel with the secondary winding of the welding transfo a transformer, and a current sensor is connected in series to the secondary circuit of the welding transformer, the output of which is connected to the thyristor control unit.

The drawing shows an electrical diagram of the inventive power source for arc welding.

The inventive power source includes a transformer 1 with a primary winding 2 and a secondary winding 3. The winding 2 circuit includes connected oppositely thyristors 4 and 5 with a control unit 6. Parallel to the thyristors 4 and 5, a chain of series-connected capacitor 7 and the primary winding 8 of the transformer is connected 9 (in prototype terms, this is an “inductor”). A choke 10 is connected in series with thyristors 4 and 5 in the primary winding 2, and a capacitor 11 is connected in parallel with thyristors 4 and 5 and winding 2. A chain of series-connected secondary windings of transformer 9 is connected to the secondary winding 3 of transformer 1 and welding electrodes 12 and 13 (in terms of the prototype this is an “additional winding”) and a capacitor 15. In addition, a current sensor 16 with windings 17 and 18 is connected in series with winding 3.

The inventive device operates as follows.

When applying a supply voltage of 220 V to the power source during the first half-wave, the current flows through the circuit: inductor 10, capacitor 7, winding 8, winding 2, and inductor 10, capacitor 11. There is a charge on capacitor 7. Voltage is applied to winding 3, which present on the electrodes 12 and 13, the block 6 remains off, since the control signal is not received from the winding 18 of the current sensor 16. A capacitor 11 is charged through the inductor 10. This is the so-called standby mode.

When the electrodes 12 and 13 are first touched, the circuit closes: electrodes 12 and 13, winding 3, winding 17. A signal appears on winding 18, which includes block 6, which in turn includes thyristor 4 (or 5). The capacitor 11 then starts to discharge to the winding 2, along with it, the capacitor 7 starts to recharge through the winding 8 and the thyristor 4 (or 5, depending on the half-wave of the supply voltage) to a voltage of opposite polarity. Having recharged, the capacitor 7 closes the thyristor 4 (or 5).

If conditions arise for the appearance of an arc during the recharging of the capacitor 7, the voltage of the winding 3 is applied to the electrodes 12 and 13 and, through the capacitor 15, the voltage of the winding 14 induced from the winding 8. The winding 14 and the capacitor 15, designed to improve the passage of the high-frequency component of the ignition pulse, form ignition pulse. When the arc is excited, the energy of the capacitor 7 is spent on the welding arc, the capacitor 7 is not recharged and no current is generated opposite to the current of the winding 2, and the thyristor 4 (or 5) will work until the end of the half-wave of the welding current. Similar processes occur with a negative half-wave voltage.

The presence of inductor 10 limits the short-circuit current, which facilitates the thermal regime of the power source, and forms a damping current-voltage characteristic of the arc. The capacitor 11 due to the accumulated energy provides a smooth increase in current from the supply network at the time of turning on of the thyristor 4.

The inductor 10, the capacitor 11 constitute a filter that suppresses the high-frequency component of the pulses that protect the mains from high-frequency noise arising from the ignition pulse. The absence of a inductor (“additional winding” in the prototype) in the secondary circuit of transformer 1, on which a voltage drop occurs when the welding current passes, can reduce the number of turns of the secondary winding 3 of transformer 1.

The proposed power source for arc welding with intermittent arc supply has lower overall dimensions, does not create high-frequency interference in the network, has higher efficiency and cos, due to the standby mode, has lower power consumption and higher durability.

Claims (1)

A power source for arc welding, containing a welding transformer, with a primary winding of which thyristors connected in parallel with the control unit are connected in series and parallel to the thyristors, a chain of series-connected capacitors and inductors magnetically connected to an additional winding included in the secondary winding of the welding transformer is connected, characterized in that it is equipped with a choke, two capacitors and a current sensor, and an inductor and its additional the winding is made in the form of a separate transformer, in which the inductor is the primary winding, and the additional winding is the secondary winding, while the inductor is connected in series with the primary winding of the welding transformer, one of the introduced capacitors is parallel to the thyristors and the primary winding of the welding transformer, the secondary winding of the separate transformer and another introduced capacitor connected in series to it is connected in parallel with the secondary winding of the welding transformer, and in nb welding transformer secondary winding successively switched current sensor, whose output is connected to the thyristor control unit.