DE1615406A1 - Welding transformer - Google Patents

Description

SIEMENS ACT. _r _ .. ngen, -

■ "". "■" ■ 'Werner-von-Siemens-Str. 50

ISI5406

i> LA 67/1593

Welding transformer -:

The invention relates to a-Schw.eißtransformatör FLIR 'welding machines _r insbes'ondere for operating with multi-phase PreQuenzmitersetzung resistance welding machines.

In the case of electrical resistance welding, as a rule single-phase alternating currents of low voltage and high amperage are used. The "standing white times" are short, ede are in

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PLA 67/1395 16154 $ 8

the order of magnitude of a few periods of the network frequency. the Secondary circuits of the machines often have considerable dimensions, which have an unfavorable effect on the power factor. This has led to efforts to balance the single-phase load and to improve the power factor.

One way of doing this is to reduce the secondary sequence by using controlled rectifiers, e.g. Thyristors. This lowering of the secondary frequency brings - if it is possible, the welding with a half-wave to be carried out - for some materials. e.g. light metals, in addition, considerable technological advantages »

During a half cycle of the secondary frequency are either the positive or the negative half-waves of the three Uetzvoltage switched to the transformer and magnetize it in one direction, in extreme cases, until a power transmission is no longer possible because of the saturation of the core. Then one rectifier group must be switched off and the reversed polarity can be switched on.

The nutable flux stroke in the 'transformer becomes essential influenced by what state of magnetization the core to The beginning of a half-wave of the low frequency had «He hangs thus to a considerable extent on the polarity and the angle of cut the previous half-wave from "

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According to the invention, an improved utilization of the core sheet is achieved achieved in that the magnetic core of the transformer before each magnetization to generate a secondary Welding current pulse with a special DC excitation applied to the core in the for; magnetization opposite direction pre-magnetized. Is doing the DC excitation chosen so that the Iransformator up to is premagnetized to magnetic saturation, then in in each case the full permissible flow range can be used; i.e. the core sheet is completely used in such a case. This then results for a certain pulse duration, that with the same power either the transformer is smaller can be made or if the transformer size remains the same, the power that can be transmitted can be selected to be greater.

Investigations have shown that at maximum premagnetization in the opposite direction to the useful flow, double the flow from the origin to the saturation can be expected. As long as the saturation value is not reached in the opposite direction, a higher pre-magnetization lengthens the maximum transmission time (the half-wave of the secondary frequency), whereas one Increase in the ohmic resistance in the secondary circuit Transfer time shortened.

If the secondary circuit remains permanently closed, a relatively large DC excitation is required in order to achieve a sufficient pre-magnetization effect in the order of seconds. Can the secondary circuit with each

cycle can only be interrupted for a short time, the ' DC current by one, depending on the desired transmission time

reduced by two powers of ten, and then only needs to be switched on in a much shorter time *

The invention will be explained in more detail with the aid of the drawing

The drawing at hand shows one with frequency reduction working three phase resistance welding machine. To the phase lines RST of a 50 Hz three-phase power supply are connected anti-parallel via protective chokes 7 per phase, controllable valves 6, in this case thyristors, connected. The output of any anti-parallel circuit is over part of the primary winding 2 of the welding

* -. "- ■ transformer 1 connected to the input of the next anti-parallel circuit. The secondary winding 3 of the welding transformer 1 is connected to the welding power consumer 5,.

If, for example, the valves 6 assigned to the positive half- wool & welding current are ignited, the current flows in the direction of the arrow 9 through the primary winding 2 of the welding transformer 1; are the valves assigned to the negative half-wave

ignited, the current flows in the opposite direction to the

Arrow 9.' -.V -.-- - - ·

Welding now works those assigned to the positive half-wave Valves 6 depending on the program a certain number of

009826/1711

Periods in the same direction. At the. End of the same line of business can at least part of the magnetic energy stored in the welding transformer in alternating mode be dismantled. Subsequently, the valves 6 assigned to the negative half-wave are then ignited described type of control of the valves 6 results in a considerable frequency reduction of the existing 50 Hz three-phase current, '.

.As a time base for controlling the valves and others Control of those occurring in the resistance welding machine Times are taken from the three-phase network in a known manner.

conducted counts used. This is not "further, because known shown. "■ '■" ...

According to the invention, there is now an additional one in the welding transformer 1 Winding 4 is provided, which is fed from a DC voltage source 8. With the help of this additional winding can the core of the welding transformer 1 after the end of the last half-wave and ^ before the start of the next welding current pulse premagnetized in the opposite direction to the magnetization that will soon follow and generate the welding current pulse will. The bias should be at least so far be driven that the associated with the welding current The stroke of the magnetic flux is symmetrical to the zero. The maximum half-wave duration is achieved if the premagnetization is used up to the saturation range of the Trahsformator-

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core drives. As not shown, of course, the respective polarity of the one applied to the additional winding 4 DC voltage to be synchronized with the control of the valves 6.

The additional winding 4 has only been simplified for the sake of simplicity Representation chosen; it was * just as possible to be in each of the primary windings or in the secondary winding or in both the secondary and primary windings Connect DC voltage for premagnetization.

2 claims
1 fig.

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Claims (1)

1611401 1. SohwelÄtransformat οτ majiehine for Sehwei @ ii, for irtajbeioiiaere with frecLuensuntersetgung working _{MehrBhaseriT-Wiiäerataiids-t} 8chwßißniaschinen characterized in that the magnetic core of the 3chweiSti? An3f © i * i? IatQFS (1) yar Jed ^ r Äwfmagnetisierung for generating one of the setendaries. Sehweißstromiinpulgeg with a special GleiohstromreiPWig | 8 »4) is onSGiilftgfea.r, which is the core in the. gu.r Aurmag | ietiaierung gegengeetztein seal 2, Schwelßtranafermat> br; according to claim 1, characterized in that that the Sieich current excitation (4 * 8) is chosen such that the Welding transformer (1) ^^ to -to magnetic 009826/1711 ^ S left side