GB2051506A - AC frequency changer - Google Patents
AC frequency changer Download PDFInfo
- Publication number
- GB2051506A GB2051506A GB8017524A GB8017524A GB2051506A GB 2051506 A GB2051506 A GB 2051506A GB 8017524 A GB8017524 A GB 8017524A GB 8017524 A GB8017524 A GB 8017524A GB 2051506 A GB2051506 A GB 2051506A
- Authority
- GB
- United Kingdom
- Prior art keywords
- converter
- thyristors
- thyristor
- output
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000003466 welding Methods 0.000 claims abstract description 38
- 239000003990 capacitor Substances 0.000 claims description 6
- 238000009499 grossing Methods 0.000 claims description 6
- 239000004065 semiconductor Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 3
- 238000004804 winding Methods 0.000 claims description 3
- 238000010276 construction Methods 0.000 claims description 2
- 230000010363 phase shift Effects 0.000 claims description 2
- 230000000087 stabilizing effect Effects 0.000 claims description 2
- 241001640034 Heteropterys Species 0.000 description 1
- 101000573901 Homo sapiens Major prion protein Proteins 0.000 description 1
- 102100025818 Major prion protein Human genes 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/523—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with LC-resonance circuit in the main circuit
- H02M7/5233—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with LC-resonance circuit in the main circuit the commutation elements being in a push-pull arrangement
- H02M7/5236—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with LC-resonance circuit in the main circuit the commutation elements being in a push-pull arrangement in a series push-pull arrangement
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/305—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a thyratron or thyristor type requiring extinguishing means
- H02M3/315—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M3/3155—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with automatic control of the output voltage or current
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Arc Welding Control (AREA)
Abstract
In an arrangement for direct- current and/or alternating-current arc welding, comprising a converter (11) for generating an alternating converter output current the frequency of which is higher than the mains frequency, the converter (11) is connected via a rectifier (10) to a three-phase supply network RST and, furthermore, its output is connected via a transformer (13) to a workpiece (15) and to a welding electrode (16). In order to make welding possible with high powers, even at high converter output current frequencies, whilst using thyristors of conventional speed, the converter (11) is provided with parallel- connected thyristor pairs (24 to 26) with resonant circuits (27, 28, 29) and also with a thyristor control unit (12) by means of which the thyristor pairs (24-26) can be driven successively in time in such a manner that positive and negative half-waves are alternately available at the converter output (50). <IMAGE>
Description
SPECIFICATION Arrangement for direct-current and/er a0- ?ernatlncJreur u are ',"'elldln The present invention relates to an arrange ment for direct-current and/or akernating-cur- rent arc welding comprising a converter for generating an alternating converter output current the frequency of which is higher than the supply frequency, the converter being connectable via a rectifier to a supply network and, furthermore, the converter output being connectable via a transformer and, if necessary, a rectifier or second converter, to a workpiece and to a welding electrode.
This pre-characterising clause refers to welding arrangements which have become known, for example, from German Offenle gungsschrirE 1 7 65 775, German Offenle- gungsschriS 26 51 510, German OWenle- gungsschrift 27 20 347, German Offenle- gungssclhrift 27 20 942 and RCA Application
Note AN 66 28, entitled "Design and AppRi- cations of igh Power Ultrasonic Converters
Using ASCR's".
The aa'vantage of these arrangements for arc welding, which have become known from the literature, is said to consist in that the converter mates it possible to raise the input frequency to the transformer following it considerably with respect to the power frequency used, for example to such an extent that the frequen' is outside the human threshold of hearing, that is to say above 18 Kilohertz.
This increase in frequency makes it possible to reduce the dimensions of the subsequent transformer, advantageously resulting in a re suction in the weight of the whole welding arrangement so that the welding arrangement is now lighter by a factor of about 10, in contrast to welding units which do not work with a converter.
In the above-mentioned literature converters are described which must generate an alternating output current having a frequency of up to 30 Kilohertz. The arrangement for arc welding of this type which has hitherto become known in practice and in which the converter is constructed with thyristors, works with a frequency of 1000 Hertz. This arrangement has the disadvantage that this frequency is within the audible range and that an unpleasant noise is produced during welding.
The prevailing use of this low and disadvantageous frequency in converters with a power which makes welding possible is likely to be due to the fact that the requirements for a high cut-off voltage and high currents in the thyristors, on withe one hand, and short commutated turn-off times, on the other hand, are mutually contradictory, for which reason semiconductor manufacturers have hitherto only been able to offer a compromise.
So that the converter can be connected to a 380-V supply network, for the required welding power, it is necessary to use thyristors having a high cut-off voltage in the converter.
Considering the achievable commutated turnof times of the thyristor, however, such thyristors cannot be operated at high frequencies (for example at more than 1 8 KHz).
From Application Note AN 66 28 thyristors have also become known which have commutated turn-off times of the order of 4 ssusec..
The cut-off voltage of these thryristors does not, however, allow them to be operated on the 380-V supply network. Connecting several of these thyristors in series is problematic at the frequencies of more than 18 Kilohertz being considered. It is possible to operate the converter on a 220-V supply network also at these high frequencies but the achievable output povver (converter efficiency = 0.8) is 2.8
KW maximum. Only lower welding currents can be obtained with this output power.
It is the object of the present invention to produce a welding arrangement of the type mentioned initially which, when operated on the 380-V supply network and at high frequencies of the alternating converter output current, makes welding possible also at high powers.
According to the invention, in order to achieve this object it is proposed that the converter is provided with parallel-connected pairs of semiconductor switching elements connected to appropriate resonant circuits and that a control unit is provided by means of which the pairs of switching elements can be driven successively in time in such a manner that positive and negative half-waves are alternately available at the converter output. The switching elements are preferably thyristors.
The circuit according to the invention has all the advantages of the "20 KHz method" and advantageously makes it possible to operate the unit from the 380-V network and at any power, and this with the use of thyristors of conventional speed which are offered in a wide range by almost all semiconductor manufacturers.
The use of thyristors of conventional speed has become possible by virtue of the special type of drive since, for example, with three pairs of thyristors each individual thyristor of a pair is at rest for the duration of two halfwaves; in a circuit with five pairs of thyristors it is even four half-waves. If the converter is working, for example, at 20 KHz, the rest period with three pairs of thyristors is for each thyristor two half-waves at 25 S each = 50 uS; with five thyristor pairs it is 100 yS.
Thyristors with circuit-commutated turn-off times in this region are available also with high cut-off voltages and high currents so that all the requirements of the objects are advantageously met by the invention. A further advantage consists in the fact that the total effective current of the converter does not have to be supplied by a single pair of thyristors but by three thyristor pairs (in this case, therefore, each thyristor only has to conduct 1/3 of the effective current) or by five thyristor pairs (here each thyristor is loaded with only 1/5 of the effective current).
The invention is explained in greater detail in the description which follows, indicating further advantageous characteristics and referring to the drawing, in which: Figures 1 and 2 shows the converter according to the invention in a half-bridge circuit, and
Figures 3 and 4 shows the converter according to the invention in a full-bridge circuit.
The arrangement for arc welding shown in the drawing is provided with a direct-current section 10 which is followed by a converter 11 with its associated control unit 1 2. The output of the converter 11 is electrically connected via a transformer 13 and a rectifier 1 4 to a workpiece 15 and a welding torch 1 6.
According to the invention, the direct-current section 10 consists of a three-phase bridge rectifier 17 which is connected to a three-phase supply network R S T and which advantageously comprises three controllable thyristors 18 and three diodes 19 (half-controlled bridge). The thyristors 1 8 are then connected to a phase-shift control unit 20 which contains a voltage stabilizing circuit and is known in itself and not shown in greater detail. Naturally, a fully-controlled three-phase bridge rectifier can also be used advantageously. In addition, the direct-voltage section 10 also comprises a smoothing unit 21 containing smoothing capacitors 22 and the smoothing choke 23. The output of the directcurrent section 10 is connected to a converter 11.
The converter 11 is provided with three parallel-connected thyristor pairs 24, 25, 26 containing the individual thyristors 24a, 24b, 25a, 25b, 26a and 26b. Each thyristor pair 24, 25 and 26 is associated with resonant circuits 27, 28 and 29 comprising the commutating capacitors 30, 31, 32 and inductances 33, 34 and 35. In these arrangements each inductance is a separate primary winding of the output transformer 1 3.
The thyristors 24a to 26b are associated with a thyristor control unit 12 by means of which the thyristors 24a to 26b can be driven successively in time in such a manner that positive and negative half-waves are alternately available at the converter output so that the output frequency is preferably greater than 18 KHz. The switching sequence of the thyristors by means of the unit 12, the construction of which is known and which is, therefore, not explained in greater detail, is: thyristor 24a, 25b, 26a, 24b, 25a and 26b.
Except for the converter 11, the illustrative embodiment of Fig. 2 corresponds to that of
Fig. 1. The converter 11 comprises five thyristor pairs 37 to 41. The resonant circuits are designated by 27, 28, 29, 50 and 51, the inductances by 33, 34-, 35, 52 and 53 and the commutating capacitors by 30, 31, 32, 54 and 55. The switching sequence according to the invention is then 37a, 38b, 39a, 40b, 41a, 37b, 38a, 39b, 40a and 41b.
In the e::ample according to Figs. 1 and 2, the thyristor pairs and the resonant circuits are provided in a half-bridge circuit. Naturaily, it also advantageously possible to use the proposal according to the invention in converters with full-bridge circuits. In Figs. 3 and 4 the appropnate converters are shown, with three or five double pairs of thyristors 42 to 441 or 45 to 49', respectively.The switching sequence is then in Fig. 3: 42a/42'b, 43b/A3'a 4ara/44'b, 42b/42'a, 43a/43'b and 44b/44'a. In Fig. 4 the following switching sequence is produced: 45a/45'b, 4615/48'a, 47a/47'b, 48b/48'a, 49a/49'b, 45b/45'a, 46a/46'b, 47b/47'a, 48a/48 and 49b/49'a.
The remaining design of Figs. 2 to 4 corresponds to that of Fig. 1 and is, therefore, not shown in Figs. 2 to 4 for reasons of clarity.
in the above-mentioned illustrative embodiments full-bridge-connected thyristor converters are provided. It is, of course, possible and lies within the scope of the invention to provide, instead of these bridge-connectec3 converters, converters with different circuit arrangements. Converters using switching elements which are not thyristors, for example using transistors as switching elements, can also be used advantageously.
The above-mentioned arrangements for arc welding are not restricted to arc welding using a non-fusible electrode but can also be used to weld with fusible electrodes according to the manual electrode welding or the gas metal-arc welding method. The arrangement according to the present invention can be employed advantageously also for submergedarc welding, plasma welding and cutting.
CLA rs 1. ' An arrangement for direct-current and/or alternating current arc welding, com- prising a converter for generating an alternating converter output current the frequency of which is higher than the supply frequency, the converter being connectable via a rectifier to a supply network and the converter output being connectable via an output transformer to a workpiece and a welding electrode wherein the converter is provided with paral lel-connected pairs of semiconductor switching elements connected to appropriate resonant circuits and a control unit by means of which the pairs of switching elements can be driven successively in time in such a manner that positive and negative half-waves are alternately available at the converter output.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (5)
1. ' An arrangement for direct-current and/or alternating current arc welding, com- prising a converter for generating an alternating converter output current the frequency of which is higher than the supply frequency, the converter being connectable via a rectifier to a supply network and the converter output being connectable via an output transformer to a workpiece and a welding electrode wherein the converter is provided with paral lel-connected pairs of semiconductor switching elements connected to appropriate resonant circuits and a control unit by means of which the pairs of switching elements can be driven successively in time in such a manner that positive and negative half-waves are alternately available at the converter output.
2. An arrangement according to claim 1,
wherein the inductance of each resonant circuit is in each case a separate primary winding of the output transformer.
3. An arrangement according to claim 1 or 2, wherein the alternating output current of the converter has a frequency which is greater than 1 8 kilo-Hertz.
4. An arrangement according to any preceding claim, wherein the semiconductor switching elements are thyristors.
5. An arrangement for direct-current and/or alternating current arc welding substantially as herein described with reference to and as illustrated by Fig. 1, Fig. 2, Fig. 3 or
Fig. 4 of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19792922144 DE2922144A1 (en) | 1979-05-31 | 1979-05-31 | DEVICE FOR DC AND / OR AC ARC WELDING WITH AN INVERTER |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2051506A true GB2051506A (en) | 1981-01-14 |
Family
ID=6072141
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8017524A Withdrawn GB2051506A (en) | 1979-05-31 | 1980-05-29 | AC frequency changer |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE2922144A1 (en) |
| FR (1) | FR2458171A1 (en) |
| GB (1) | GB2051506A (en) |
| IT (1) | IT1131436B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2310553A (en) * | 1995-02-28 | 1997-08-27 | Fuji Electric Co Ltd | Noise filter for inverter |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3247523A1 (en) * | 1982-12-22 | 1984-07-05 | Vsesojuznyj naučno-issledovatel'skij i proektno-konstruktorskij institut gornorudnogo mašinostroenia "VNIPIRUDMAŠ", Krivoi Rog | Method and device for controlling the welding process in the case of a power supply for mine DC traction lines |
| DE4411227A1 (en) * | 1994-03-31 | 1995-10-05 | Elektro Werk Muendersbach Gmbh | Arc welding appts. with resonance switching circuit |
| WO1996011766A1 (en) * | 1994-10-13 | 1996-04-25 | Nikolai Borisovich Marchenko | Method of forming a welding current and a device for carrying out said method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3304484A (en) * | 1965-12-13 | 1967-02-14 | Westinghouse Electric Corp | Valve extinguishing network for inverters |
| US3846695A (en) * | 1973-05-07 | 1974-11-05 | Honeywell Inf Systems | Series-parallel dual switching regulator for use with a variety of line voltages |
-
1979
- 1979-05-31 DE DE19792922144 patent/DE2922144A1/en not_active Withdrawn
-
1980
- 1980-04-29 FR FR8009696A patent/FR2458171A1/en not_active Withdrawn
- 1980-05-07 IT IT21841/80A patent/IT1131436B/en active
- 1980-05-29 GB GB8017524A patent/GB2051506A/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2310553A (en) * | 1995-02-28 | 1997-08-27 | Fuji Electric Co Ltd | Noise filter for inverter |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2922144A1 (en) | 1980-12-04 |
| FR2458171A1 (en) | 1980-12-26 |
| IT1131436B (en) | 1986-06-25 |
| IT8021841A0 (en) | 1980-05-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |