SU1542721A1 - Power supply source for arc welding - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to electrical equipment for arc welding, and can be used for welding with rectangular alternating current with independent control of the durations of the current pulses of direct and reverse polarity. The purpose of the invention is to expand the technological capabilities of the power source and improve the quality of welding. The power supply contains a transformer, a power thyristor bridge with a choke in its diagonal and a control unit. Two thyristor bridges are introduced into the source, which are connected by their inputs to the terminals of the secondary winding of the transformer, and the outputs are interconnected in parallel with each other and in series with the power thyristor bridge and the load. The thyristors of the additional bridges carry out a full-wave rectification of the secondary voltage of the transformer. Pulses of one or another polarity enter the load through the thyristors of the power bridge and the choke connected in pairs. The pulse duration is determined by the operation time of each of the additional bridges. The power source has the ability to modulate the welding current, which, under conditions of independent control of the pulse durations of the direct and reverse polarity, leads to an improvement in the quality of the welded joint. 2 Il.

Description

The invention relates to electrical engineering, in particular to electrical equipment for arc welding, and can be used for AC welding of a rectangular shape with an adjustable pulse width of direct and reverse polarity.

The purpose of the invention is to expand the technological capabilities of the power source and improve the quality of welding by providing independent control of the durations of the current pulses of direct and reverse polarity.

FIG. 1 shows a basic electrical power supply circuit.

for arc welding; in fig. 2 - welding current change curve.

The power source welding circuit (Fig. 1) consists of three bridge circuits assembled on thyristors 1-12, loads (arcs) 13 and the secondary winding of transformer 14.

Thyristors 1-8, form the first. (1-4) and second (5-8) additional rectifying bridges, which by their inputs are connected to the terminals of the secondary winding of the transformer 14, and the outputs are connected anti-parallel to each other and in series with power thyristor bridge (9-12) containing throttle

4 CE 1 N3

Sel 15 in the diagonal, and the load (arc) 13. The control unit for simplifying the scheme is not shown.

The power source works as follows.

When a positive potential appears at the upper output of the secondary winding of the transformer 14 and the flow of control pulses from the control unit to the 1, 4, 10 and 11 of the control unit opens, the current flows through the circuit: the second winding - I - load 13 - 10 - choke 15 - 1 - 4 - secondary winding.

1 In the next half-period, the thyristors 2 and 3 are turned on, and the thyristors 1 and 4 are switched off. Thus, the thyristors 1 - 4 carry out a full-wave rectification of the secondary voltage of the transformer – mountain 14, and in the load 13 through the included thyristors 10, 11 and throttle 5, direct polarity current pulses ("minus at the electrode) are received, the duration of which is determined by the time of operation of the first additional bridge on thyristors 1-4.

The polarity of the welding current is changed as follows.

Let the thyristors 1, 4, 10, 11 work at the considered moment of time. The thyristors 1 and 4 were switched on with a positive potential on the upper one according to the circuit | output of the transformer secondary winding. | In the next half period, the voltage at the terminals of the secondary winding of the transformer changes sign. When applying control (pulses to thyristors 5 and 8 of Eggorogo (Additional bridge, which are connected in parallel to parallel to thyristors 1 and 4 of the first additional washing, and also to thyristors 9 and 12 of the power bridge, 9 and 12 are turned on, and thyristors 1, 4, 10, and 11 are turned off. At the same time, the current in the load abruptly changes sign. - 12 - load 13 - 5 - transformer secondary winding. Thyristors 6 and 7 are switched on for half time, and thyristors 5 and 8 are turned off. Thus, thyristors 5-8 also carry out a full-wave second

0

from 0

about 5 5

five

0

transformer 14, and the load 13 through the switched on thyristors 9, 12 and the choke 15 receives current pulses of reverse polarity, the duration of which is determined by the operating time of the second rectifying bridge on thyristors 5-8.

Compared with the base prototype object, in the proposed source the duration of the pulses of the direct and reverse polarities can be controlled independently of each other within wide limits. The control resolution is half the period of the supply voltage, however, with a different number of half-periods in the pulses of direct and reverse polarity, it is possible to control the durations of the pulses within one half-period without dangerous saturation of the transformer magnetic circuit. At the power source, there is the possibility of modulating the welding current, and under conditions of independent control of the durations of the current pulses of the direct and reverse polarity, the efficiency of the modulation mode increases significantly.

If necessary, the transition to the DC welding mode of any polarity is carried out without mechanical switching of the welding cables, which also expands the technological capabilities of the proposed scheme.

Claims (1)

Invention Formula A power source for arc welding, containing a transformer, a power thyristor bridge connected in series with the secondary winding of the transformer, a choke in the diagonal of the power thyristor bridge, and a control unit, characterized in that, in order to expand the technological capabilities of the source and improve the quality of welding by providing independent controlling the durations of current pulses of direct and reverse polarity, it is equipped with two thyristor bridges, which are connected by their inputs to the terminals of the secondary circuit. The transformer webs, and the outputs are interconnected in relation to each other and in series with the power thyristor bridge and load. Ј-i / 4 fig 1 FIG. 2