Two-phase induction welding generator

FIELD: process engineering.

SUBSTANCE: proposed invention can be used in hand-held electric arc welding devices. Induction welding generator has two-winding stator. Three-phase excitation winding 2 has terminals for excitation capacitors 3 to be connected thereto. Working winding 4 is a two-phase winding. Circuit of said winding each phase 4, 5, shifted through 90 degrees, incorporates compound capacitor 6, 7 and single-phase bridge rectifier 8, 9 shunted by shunting capacitors 10, 11. Output terminals of rectifiers 8, 9 are connected in parallel and welding electrode 12 is connected thereto.

EFFECT: increased welding current.

3 dwg

The invention relates to electrical engineering, in particular to asynchronous electric machines with capacitor excitation, and can be used in the devices manual arc welding.

Known for the design of asynchronous welding generator with two polyphase windings on the stator, one of which is the excitation winding has terminals for connecting the capacitor battery, the other is working and has terminals for connection to the welding device [1]. The working winding offset angle α al. grad. relative to the winding direction of rotation of the rotor. To the phase winding connected to the primary winding compounding transformer, and to the similar phases of the working winding - secondary winding of this transformer.

One disadvantage of this generator is the presence of compounding transformer, which increases the mass of the entire welding installation and reduce overall efficiency. Another disadvantage is that the resistance of the circuit "the field winding, the primary winding compounding transformer - capacitor Bank" depends on the mode of operation of the generator. When there is no load (idling) the resistance of the primary winding compounding transformer is very large, but in the mode of short circuit (SC) is whether nominal load - is very small. In effect this becomes problematic excitation, and the generator operation mode of low load and idling (XX). For manual arc welding generator at the beginning of the mode XX, then, after a contact of the electrode with the workpiece, goes into a mode short circuit, and after the ignition of the arc is working in nominal mode. Thus, the difficulties encountered in the mode XX, make this generator is not suitable for manual arc welding. The presence of switches which mode XX continuum primary winding compounding transformer, does not improve the situation, since the switches not only complicate the design of the generator, but should, during each cycle of welding to close and rasmijoti your contacts. It should be noted that the external characteristics of the generator does not intersect the axis voltage [1]. This is indirect confirmation of the above.

A known design of a contactless welding generator [2], which has a squirrel-cage rotor and two three-phase windings on the stator. To the first winding through a rectifier and a choke connected load (arc). The second winding is connected capacitors excitation, and the conclusions of this winding can be used to supply the consumers three-phase AC voltage.

The disadvantage of this generator which is in idle mode magnetizing current exceeds the rated several times.

This is because to ensure the rated induction in the gap generator mode XX requires one value of the capacitors, and in the mode of short circuit or load another, and more. Therefore, when the fixed-capacitance capacitor that is selected for operation with rated load, the mode XX accompanied by an increase in the magnetizing current and significant saturation of the magnetic system of the generator.

It should be noted that this disadvantage is inherent in asynchronous generator of conventional design. The use of fast-acting reactive power regulator, able to solve the task, will lead to a significant complication of the generator will decrease reliability and increase the weight.

The prototype of the present invention is a contactless asynchronous welding generator [3]. This generator has two three-phase windings on the stator. One winding is the winding. To its terminals connected capacitors excitation, which ensure the operation of the generator at idle and under load. The other winding is working. The early phases of the working winding has terminals for connection of shunt capacitors and rectifier, the output of which is connected to the welding electric is od and the ends of phases of the winding has terminals for connection compendiously capacitors connected in a triangle.

The presence compendiously capacitors can reduce losses and improve efficiency by reducing the demagnetizing action of the welding current of the working winding.

The disadvantage of this generator is the low voltage compendiously capacitors and, as a consequence, the low efficiency of their use. This is because the allowable open circuit voltage welding current source for arc welding should not exceed U_dXX<100 B [4, p.28]. Accordingly limited phase open-circuit voltage working windings of the generator, which, for example, when U_dXX=80 will be equal to U_2XX=U_dXX/2,34=34,19 Century, the Greatest voltage compendiously capacitors occurs during a short circuit in the load circuit. In this mode compendiosa capacitors prototype connected in a triangle, fall under the line voltage, which increases due to the additional reactive power of these capacitors. Suppose that the growth was 30% compared with the open-circuit voltage working windings. Under this assumption, the voltage applied to compounders capacitors prototype, will be equal to. In turn, the smallest is minalee the modern power voltage polypropylene capacitors, for example, a series of K78-17, at frequency of 50 Hz is 250 B, and at a frequency of 200 Hz - 165 B. As the reactive power of the capacitors is proportional to the square of the voltage, in the first case, the serial capacitors will develop 9.5% of the rated reactive power, and the second 22%.

The technical result, which provides the claimed invention, is to increase the welding current due to more efficient use of the serial capacitors designed for compounding generator.

This technical result is reached by the fact that asynchronous welding generator with two windings on the stator, one of which is the three-phase excitation winding has terminals for connection of capacitors excitation, the other is a working winding, and a working winding is a two-phase, in the circuit of each of the phases of the windings shifted by 90 El. degrees, consistently included compendiosa capacitors and single-phase bridge rectifier shunted by shunt capacitors, terminals of the rectifiers are connected in parallel and connected to the welding electrode.

Electric circuit asynchronous welding generator is presented in figure 1. Figure 2 shows the external features and operating voltage on compendiously capacitors claimed generator and prototype. Revie the transition process when a short circuit is presented in figure 3.

The generator has a squirrel-cage rotor 1 normal structures (figure 1). In the slots of the stator of the asynchronous welding generator stacked three-phase excitation winding 2 and the working coil, which has two phases 4, 5. The number of turns of the winding 2 are selected in such a way as to ensure optimal use of voltage capacitors excitation 3. In the circuit of the first phase of the working winding 4 series compendiosa capacitors 6, single-phase bridge rectifier 8, shunted by shunt capacitors 10. The second phase of the working winding 5 respectively connected compendiosa capacitors 7, the rectifier 9 and the shunt capacitor 11. Conclusions DC rectifiers 8 and 9 are connected in parallel. Phase 4, 5 of the working windings have the same number of turns. The capacitance of the capacitors in phases 4 and 5 are also equal. The same parameters and have the rectifiers 8, 9. The number of turns in the phase of the working winding depends on the desired circuit voltage welding electrode 12.

The generator works as follows. When the rotor 1 of the driving motor (internal combustion engine, electric motor) residual flux induces an EMF in the windings of the stator. Under the action of the voltage in the capacitors 3 capacitive current which, flowing through the excitation winding 2 increases poles gap, that, in turn, leads to increased EMF etc. Snowballing process of growing EMF (asynchronous process of self-excitation) ends when the saturation of the generator, when it starts to run in steady state with capacitor excitation. In the windings of the generator set voltage, which is proportional to the number of turns of the respective windings and the capacitance value of the capacitor excitation. 3. When reducing the load resistance increases the current of the working winding. This increases the reactive power compendiously capacitors 6, 7 and therefore, the generator loses excitation and stable operation even when a short circuit. When load shedding energy compendiously capacitors is dissipated by the circuit, which is created by shunt capacitors 10, 11. In addition, these capacitors allow you to adjust the open circuit voltage and generate dynamic characteristics of the generator. So, if you increase their capacity voltage in idle mode welding electrode decreases, and when the electrode touch the workpiece (short circuit) increases, the peak current.

For single-phase bridge rectification fair the following formula:[5, p.58]. Here U_d- average rectified voltage, U_1F- single-phase alternating voltage is a group of the input to the rectifier. To each of the parallel-connected bridge rectifiers 8, 9 are summed voltage, which is shifted in phase by 90 degrees. For this circuit we can write:where U_2F- phase voltage-phase system. Three-phase bridge rectifier, which is used in the prototype is:[5, 67]. Here U_3F- phase voltage three-phase system. Comparing the last two formulas shows that for the same value of the average rectified voltage AC voltage applied to the rectifiers two-phase induction welding generator, U_2F/U_3F=1.3 times greater than that of the prototype. Accordingly, the proposed generator will phase voltage working windings, and hence the DC component of the rectified current. This is confirmed by the results of the calculation of the external characteristics of the claimed generator (curve 13) and prototype (curve 14), presented in figure 2. In the calculation it was assumed that the generators have the same magnetic system, the current density in the windings, the magnetic induction in the air gap and the corresponding total capacitance of the capacitors of all phases (initiation, compendiously, shunt), i.e. ΣC_WSBF=ΣC_WSBF, ΣC_kompf=ΣC_kompf, ΣC_{shunt the} =ΣC_SunTV. The dependence of the voltage on compendiously capacitors from the welding current are presented in figure 2 in the form of curves 15 and 16. These curves show that for the same values of voltage welding current at the stated generator and more.

Such regularity with currents saved as when operating in steady state welding, and in case of short circuit. Assume that the operating arc voltage and welding current are related by the equation: U_p=20+0,04I_d[4, s, s] (line 17), then in steady state the two-phase current of the generator is equal to I_d.2=132 A (point a), and the prototype - I_d.3=112 A (point b). In case of short circuit respectively have the following currents: I_d..2=159 A (point c); I_d..3=127 A (point d). The current growth in the first case was 17.85%, and the second 25%. When operating in these modes, the voltage on compendiously the capacitors of the two-phase generator is greater than that of the prototype (points e-f, g-h). The increase in voltage on compendiously capacitors are not so significant compared with a preliminary calculation, as in this case takes into account the effect of saturation and the voltage drop in the circuit of the generator.

Thus, when the same magnetic systems, the current density in the windings, the same voltages on compendiously capacitors and other conditions being equal, welding t is to have a two-phase generator more than the three-phase prototype. Therefore, the claimed generator more efficiently use the serial capacitors at their work as compendiously capacitors.

3 shows the voltage curves 18, 19 and current 20, 21 in the welding circuit and compendiously the capacitors 22, 23 when a short circuit with resistance R_d=0.01 Ohms. Curves 19, 21, 23 belong to the two-phase generator, and 18, 20, 22 to the prototype. The voltage on compendiously capacitors 23 and the current 21 two-phase generator is greater than that of the prototype (curves 22, 20). Dynamic characteristics of the generators differ slightly.

The disadvantages of this solution should include a larger value of the pulse number k_PP=13.3 per cent, against k_PP=5.7% of the prototype [5, p.75], which may slightly affect the welding quality.

SOURCES of INFORMATION

1. A.S. 1798863 the USSR, H02K 17/00. Asynchronous welding generator / Philostratos, Century-Wajale, Acculaser, Lpimage, Coumarates, Saudargas, Aieoiai, Avestas. No. 4845636/07; Saw; Publ. 28.02.93. Bull. No. 8.

2. Pat. No. 237406, GDR, H02K 47/10. Burstenljser schweib generator / Julke Edmund, Dassel Jurgen; VEB Mansfeld - Kombinat Wilhelm Pick.¹2763853; Appl. 16.05.85, publ. 09.07.86.

3. Patent RU No. 2211519, H02K 17/00, H02P 9/46, B23K 9/00. Asynchronous welding generator. / A-Surgitube. No. 2001124752/09; Publ. 27.08.03. Bull. No. 24.

4. Equipment for arc St. the RCTs: a reference Handbook / edited You. - L.: Energoatomizdat. 1986.

5. Rozanov J.K. Fundamentals of power electronics. - M.: Energoatomizdat, 1992.

Asynchronous welding generator with two windings on the stator, one of which is in the form of a three-phase winding has terminals for connection of capacitors excitation, and the other is a working winding, characterized in that the working winding is made of a two-phase, in the circuit of each phase of which is shifted by 90°, consistently included compendiosa capacitors and single-phase bridge rectifier shunted by shunt capacitors at the terminals of the rectifiers are connected in parallel and connected to the welding electrode.