CA1183578A - Source of electrical energy for a resistance-welding machine - Google Patents
Source of electrical energy for a resistance-welding machineInfo
- Publication number
- CA1183578A CA1183578A CA000402770A CA402770A CA1183578A CA 1183578 A CA1183578 A CA 1183578A CA 000402770 A CA000402770 A CA 000402770A CA 402770 A CA402770 A CA 402770A CA 1183578 A CA1183578 A CA 1183578A
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- source
- electrical energy
- welding
- energy according
- 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.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/24—Electric supply or control circuits therefor
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Power Engineering (AREA)
- Generation Of Surge Voltage And Current (AREA)
- Resistance Welding (AREA)
- Inverter Devices (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
- Adjustable Resistors (AREA)
- Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
Abstract
ABSTRACT
An electrical power source for resistance welding apparatus is described. It is conventional in such a power source to use a static inverter and a welding transformer and to incorporate a static frequency converter, usually solid state, which derives an output voltage having a frequency and pulse shape different from the voltage fed to the inverter. According to the invention, one or more parallel additional frequency converters are provided. The output voltages of all the frequency converters are added in phase synchronism in the primary circuit of the welding transformer. The use of at least two frequency converters permits very steep sided pulses to be obtained thus ensuring accurate weld beginnings and ends. The shape, amplitude and work to space ratio of the pulses can be varied within wide limits.
An electrical power source for resistance welding apparatus is described. It is conventional in such a power source to use a static inverter and a welding transformer and to incorporate a static frequency converter, usually solid state, which derives an output voltage having a frequency and pulse shape different from the voltage fed to the inverter. According to the invention, one or more parallel additional frequency converters are provided. The output voltages of all the frequency converters are added in phase synchronism in the primary circuit of the welding transformer. The use of at least two frequency converters permits very steep sided pulses to be obtained thus ensuring accurate weld beginnings and ends. The shape, amplitude and work to space ratio of the pulses can be varied within wide limits.
Description
3~7~
The invention relates -to a source of elec-trical energy having a static inverter and a welding transformer for a resis-tance-welding machine, in which use is made oE a first static solid state frequency converter, the alternating output voltage of which has a frequency and pulse shape which differ from the frequency and pulse shape of the supply voltage fed to the inver-ter.
A source of energy of this kind has already been des-cribed in United S-tates Patent No. 3,553,567 which issued January 5, 1971 to Pesce et al. This source of energy produces high frequency welding currents, the pulse shape of which resembles a rectangle or square. However, the unit is satisfac-tory only to a limited extent, since the pulse shape can be varied only within narrow limits. In this known source of energy there is no way of regulating the welding energy transferred.
It is the object of the invention to provide a source of electrical energy in which the pulse shape, amplitude and work to space ratio of the welding current can be varied within wide limits and can meet the relevant requirements during welding.
According to the invention, there is provided a source of electrical energy having a static inverter and a wel~ling trans-former for a resistance-welding machine in which use is made of a first static frequency converter, the alternating output voltage of whichhas a frequency and pulse shape which differs from the frequency and pulse shape of the supply voltage fed to the inverter, at least a second frequency converter is connec-ted in parallel t~ the first frequency converter, and the al-ter-3~
nating output voltage of the at least second frequency converter is arranged to be added in phase synchronism -to -the alterna-ting output voltage oE the first frequency converter in the primary circuit of the welding transformer, wherein each frequency conver-ter consists of a transistor control stage and a thyristor power stage, the transistor control stage being preceded by a direct current bridge, the transistor control stage and the thyristor power stage being connected to the outpu-t of a frequency regula~
tor which has an input for setting a set value signal of the frequency of the welding current, the tra:nsistor con-trol stage being in addition connected to the outpu-t of a welding current regulator providi.ng an adjusting signal, the welding current regulator having one input each for setting a set value signal of the welding current and for an output signal, supplied by a measured value transdueer, which is propor-tional to the rated value of the weldi:ng eurrent.
The amplitudes of the output voltages of both frequeney - -la-~, 3~7~
converters may be constant or variable or only that of the first frequency converter variable.
The pulse shape is rectangular in the preferred embodi-ment and the work to space ratio is variable~
Providing the source of energy with at least two similar frequency converters, the alternating output voltages of which are adapted to be added, in phase synchronization, in the primary circuit of a welding transformer, makes it possible to obtain ~i pulse shapes having very s~ sides, thus ensuring accurate weld beginnings and accurate switching of weld endings. Furthermore, the steepness of the sides of the welding current increase in the secondary circuit of the welding transformer permits welding at a very low frequency, even at high production speeds. The time taken to reverse the welding current is negligable, and the frequency therefore has almost no effect upon the quality of the weld seam. If a low frequency welding current is used (below fs =
100 Hz), inductive eddy-current losses are largely eIiminated.
Accurate metering of welding energy can be achieved by providing in either the primary or the secondary circuit of the transformer a transducer having an output signal which is proportional to the rated value of the welding current and which is fed to a welding current regulator, and in that the output from the regulator is connected to the frequency converters for adjusting the ~requency converters.
Since the frequency converters are of similar design, it is a simple matter to connect in parallel as many frequency converters as are necessary to achieve rapid increase in current and rapid reversal.
~ ~3~ii7~3 The invention will now be described in greater de-tail with reference to the accompanying drawings, in which:
Figure 1 is a block diagram of a power source according to the invention;
Figure 2a is a graph of -transformer primary voltage against time; and Figure 2b is a graph of transformer secondary voltage against time.
Figure 1 shows a source of electrical energy consisting principally of a first frequency converter 10 and a second fre-quency converter 11. The outputs from the two converters are connected to the primary circuit of a welding transformer 12, while the inputs thereto are connected to a 3 x 380 V -three-pilase current supply, for example. The three-phase current passes through isolating transformers 13, 14 to conventional rectifying bridges 15, 16 which produce a direct voltage, by means of which the actual inverter stages, each consisting of a transistor control stage 17 or 18 and a thyristor power stage 19 or 2G, are fed.
The design and operation of the two latter stages are described in principle in Swiss Patent 559,~62, granted on January 15, 1975 to Marcel Etter.
The source of energy according to the invention also comprises a welding current regulator 21 and a frequency regulator 22 which are components of an electronic control system not shown in detail. Welding current regula-tor 21is connec-ted -to a feed-back loop which permits determination of a rated current value, 7~
either in the secondary circui-t by a measured value transducer 23 or in the pr~mary current by a similar transducer 24.
, ~, ..
~ ~3S~
According to the setting, frequency regulator 22 determines the frequency of the welding current which flows through electrode rollers 25 and the workpiece therebetween, not shown in the drawing.
The operating principle of the source of energy described hereinbefore is explained hereinafter with the aid of Figure 2.
In Figure 2a, voltage ul appearing at the primary circuit of welding transformer 12 is shown, while Figure ~b shows the relevant welding current i2 in the secondary circuit of the transformer. A voltage pul~e of specific length and amplitude may be produced by one of the frequency converters 10, 11. The phase synchronous addition of two of such voltage pulses gives, in the present example, the point at which welding current i2 begins to flow in the secondary circuit. The welding current very quickly reaches its set amplitude and this is kept constant by welding current regulator 21. In order to maintain the constant value of the welding current during a half-wave, fre~uency converters 10, 11 produce alternate voltage pulses which produce, in the second-ary circuit, slight modulations, according to amplitude, of ~elding current i2 with a relatively high frequency. Upon completion of the first half-wave of rectangular welding current i2, both frequency converters 10, 11 are connected, in phase synchronism and additively, to the primary circuit of welding transformer 12 (see Figure 2a), so that a reversal of the said welding current takes place in a negligably short time.
The source of energy according to the invention makes it possible to produce weldiny currents of an almost direct current ~33~
nature in relation to the edges to be welded~ which makes the present invention suitable for the execution of the method described in our Canadian Patent Application Serial No. 370,688 filed February 11, 1981. In this connection, the invention is characterized in that the welding transformer is designed for a lower transferable limit frequency which is determined mainly by the ratio between the speed of transfer and the length of the edges to be welded, and in that the dimensions of the weakly magnetic sheeting material are within a range such as to permit determination of the operating point on the characteristic magnetic curve in the B/H diagram at the beginning of the linear section. Welding currents having higher frequencies, for example mains frequency, may also be produced, the effect of welding current frequency upon the quality of the weld seam, as a function of production velocity (welding speed) being insigni:Eicant.
The invention relates -to a source of elec-trical energy having a static inverter and a welding transformer for a resis-tance-welding machine, in which use is made oE a first static solid state frequency converter, the alternating output voltage of which has a frequency and pulse shape which differ from the frequency and pulse shape of the supply voltage fed to the inver-ter.
A source of energy of this kind has already been des-cribed in United S-tates Patent No. 3,553,567 which issued January 5, 1971 to Pesce et al. This source of energy produces high frequency welding currents, the pulse shape of which resembles a rectangle or square. However, the unit is satisfac-tory only to a limited extent, since the pulse shape can be varied only within narrow limits. In this known source of energy there is no way of regulating the welding energy transferred.
It is the object of the invention to provide a source of electrical energy in which the pulse shape, amplitude and work to space ratio of the welding current can be varied within wide limits and can meet the relevant requirements during welding.
According to the invention, there is provided a source of electrical energy having a static inverter and a wel~ling trans-former for a resistance-welding machine in which use is made of a first static frequency converter, the alternating output voltage of whichhas a frequency and pulse shape which differs from the frequency and pulse shape of the supply voltage fed to the inverter, at least a second frequency converter is connec-ted in parallel t~ the first frequency converter, and the al-ter-3~
nating output voltage of the at least second frequency converter is arranged to be added in phase synchronism -to -the alterna-ting output voltage oE the first frequency converter in the primary circuit of the welding transformer, wherein each frequency conver-ter consists of a transistor control stage and a thyristor power stage, the transistor control stage being preceded by a direct current bridge, the transistor control stage and the thyristor power stage being connected to the outpu-t of a frequency regula~
tor which has an input for setting a set value signal of the frequency of the welding current, the tra:nsistor con-trol stage being in addition connected to the outpu-t of a welding current regulator providi.ng an adjusting signal, the welding current regulator having one input each for setting a set value signal of the welding current and for an output signal, supplied by a measured value transdueer, which is propor-tional to the rated value of the weldi:ng eurrent.
The amplitudes of the output voltages of both frequeney - -la-~, 3~7~
converters may be constant or variable or only that of the first frequency converter variable.
The pulse shape is rectangular in the preferred embodi-ment and the work to space ratio is variable~
Providing the source of energy with at least two similar frequency converters, the alternating output voltages of which are adapted to be added, in phase synchronization, in the primary circuit of a welding transformer, makes it possible to obtain ~i pulse shapes having very s~ sides, thus ensuring accurate weld beginnings and accurate switching of weld endings. Furthermore, the steepness of the sides of the welding current increase in the secondary circuit of the welding transformer permits welding at a very low frequency, even at high production speeds. The time taken to reverse the welding current is negligable, and the frequency therefore has almost no effect upon the quality of the weld seam. If a low frequency welding current is used (below fs =
100 Hz), inductive eddy-current losses are largely eIiminated.
Accurate metering of welding energy can be achieved by providing in either the primary or the secondary circuit of the transformer a transducer having an output signal which is proportional to the rated value of the welding current and which is fed to a welding current regulator, and in that the output from the regulator is connected to the frequency converters for adjusting the ~requency converters.
Since the frequency converters are of similar design, it is a simple matter to connect in parallel as many frequency converters as are necessary to achieve rapid increase in current and rapid reversal.
~ ~3~ii7~3 The invention will now be described in greater de-tail with reference to the accompanying drawings, in which:
Figure 1 is a block diagram of a power source according to the invention;
Figure 2a is a graph of -transformer primary voltage against time; and Figure 2b is a graph of transformer secondary voltage against time.
Figure 1 shows a source of electrical energy consisting principally of a first frequency converter 10 and a second fre-quency converter 11. The outputs from the two converters are connected to the primary circuit of a welding transformer 12, while the inputs thereto are connected to a 3 x 380 V -three-pilase current supply, for example. The three-phase current passes through isolating transformers 13, 14 to conventional rectifying bridges 15, 16 which produce a direct voltage, by means of which the actual inverter stages, each consisting of a transistor control stage 17 or 18 and a thyristor power stage 19 or 2G, are fed.
The design and operation of the two latter stages are described in principle in Swiss Patent 559,~62, granted on January 15, 1975 to Marcel Etter.
The source of energy according to the invention also comprises a welding current regulator 21 and a frequency regulator 22 which are components of an electronic control system not shown in detail. Welding current regula-tor 21is connec-ted -to a feed-back loop which permits determination of a rated current value, 7~
either in the secondary circui-t by a measured value transducer 23 or in the pr~mary current by a similar transducer 24.
, ~, ..
~ ~3S~
According to the setting, frequency regulator 22 determines the frequency of the welding current which flows through electrode rollers 25 and the workpiece therebetween, not shown in the drawing.
The operating principle of the source of energy described hereinbefore is explained hereinafter with the aid of Figure 2.
In Figure 2a, voltage ul appearing at the primary circuit of welding transformer 12 is shown, while Figure ~b shows the relevant welding current i2 in the secondary circuit of the transformer. A voltage pul~e of specific length and amplitude may be produced by one of the frequency converters 10, 11. The phase synchronous addition of two of such voltage pulses gives, in the present example, the point at which welding current i2 begins to flow in the secondary circuit. The welding current very quickly reaches its set amplitude and this is kept constant by welding current regulator 21. In order to maintain the constant value of the welding current during a half-wave, fre~uency converters 10, 11 produce alternate voltage pulses which produce, in the second-ary circuit, slight modulations, according to amplitude, of ~elding current i2 with a relatively high frequency. Upon completion of the first half-wave of rectangular welding current i2, both frequency converters 10, 11 are connected, in phase synchronism and additively, to the primary circuit of welding transformer 12 (see Figure 2a), so that a reversal of the said welding current takes place in a negligably short time.
The source of energy according to the invention makes it possible to produce weldiny currents of an almost direct current ~33~
nature in relation to the edges to be welded~ which makes the present invention suitable for the execution of the method described in our Canadian Patent Application Serial No. 370,688 filed February 11, 1981. In this connection, the invention is characterized in that the welding transformer is designed for a lower transferable limit frequency which is determined mainly by the ratio between the speed of transfer and the length of the edges to be welded, and in that the dimensions of the weakly magnetic sheeting material are within a range such as to permit determination of the operating point on the characteristic magnetic curve in the B/H diagram at the beginning of the linear section. Welding currents having higher frequencies, for example mains frequency, may also be produced, the effect of welding current frequency upon the quality of the weld seam, as a function of production velocity (welding speed) being insigni:Eicant.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A source of electrical energy having a static inverter and a welding transformer for a resistance-welding machine in which use is made of a first static frequency converter, the alternating output voltage of which has a frequency and pulse shape which differs from the frequency and pulse shape of the supply voltage fed to the inverter, at least a second frequency converter is connected in parallel to the first frequency conver-ter, and the alternating output voltage of the at least second frequency converter is arranged to be added in phase synchronism to the alternating output voltage of the first frequency conver-ter in the primary circuit of the welding transformer, wherein each frequency converter consists of a transistor control stage and a thyristor power stage, the transistor control stage being preceded by a direct current bridge, the transistor control stage and the thyristor power stage being connected to the output of a frequency regulator which has an input for setting a set value signal of the frequency of the welding current, the transistor control stage being in addition connected to the output of a welding current regulator providing an adjusting signal, the welding current regulator having one input each for setting a set value signal of the welding current and for an output signal, supplied by a measured value transducer, which is proportional to the rated value of the welding current.
2. A source of electrical energy according to claim 1, wherein the amplitudes of the alternating output voltages of the frequency converter are variable.
3. A source of electrical energy according to claim 1, wherein the amplitude of the alternating output voltage of the first frequency converter is variable and that the amplitude of the alternating output voltage of the second frequency conver-ter is constant.
4. A source of electrical energy according to claim 1, wherein the amplitudes of the alternating output voltages of the frequency converters are constant.
5. A source of electrical energy according to claim 1, 2 or 3, wherein the work to space ratios of the alternating out-put voltages of the frequency converters are variable.
6. A source of electrical energy according to claim 1, 2 or 3, wherein the pulse shapes of the alternating output vol-tages of the frequency converters are rectangular.
7. A source of electrical energy according to claim 1, 2 or 3, wherein the secondary circuit of the welding transformer is wired to the measured value transducer.
8. A source of electrical energy according to claim 1, 2 or 3, wherein the primary circuit of the welding transformer is wired to the measured value transducer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP81103674.8 | 1981-05-13 | ||
| EP81103674A EP0064570B2 (en) | 1981-05-13 | 1981-05-13 | Electric energy source for a resistance welding machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1183578A true CA1183578A (en) | 1985-03-05 |
Family
ID=8187710
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402770A Expired CA1183578A (en) | 1981-05-13 | 1982-05-12 | Source of electrical energy for a resistance-welding machine |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0064570B2 (en) |
| JP (1) | JPS58500702A (en) |
| AT (1) | ATE15617T1 (en) |
| BR (1) | BR8207698A (en) |
| CA (1) | CA1183578A (en) |
| DE (1) | DE3172302D1 (en) |
| DK (1) | DK159011C (en) |
| ES (1) | ES511904A0 (en) |
| WO (1) | WO1982004000A1 (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU587165B2 (en) * | 1984-06-15 | 1989-08-10 | Square D Company | Resistance welder |
| IT1179889B (en) * | 1984-12-21 | 1987-09-16 | Comau Spa | RESISTANCE ELECTRIC WELDING EQUIPMENT |
| US5196668A (en) * | 1988-11-17 | 1993-03-23 | Honda Giken Kogyo Kabushiki Kaisha | DC resistance welding apparatus |
| US5229567A (en) * | 1988-11-17 | 1993-07-20 | Honda Giken Kogyo Kabushiki Kaisha | Switching control system for controlling an inverter of a spot resistance welding apparatus |
| GB2225909B (en) * | 1988-11-17 | 1993-11-24 | Honda Motor Co Ltd | DC resistance welding apparatus |
| JPH0780058B2 (en) * | 1989-12-18 | 1995-08-30 | 本田技研工業株式会社 | DC resistance welding equipment |
| JPH03189079A (en) * | 1989-12-18 | 1991-08-19 | Honda Motor Co Ltd | Dc resistance welding equipment |
| JPH0780059B2 (en) * | 1989-12-19 | 1995-08-30 | 本田技研工業株式会社 | DC resistance welding equipment |
| IT1242893B (en) * | 1990-12-27 | 1994-05-18 | Cefin Spa | ELECTRONIC DEVICE FOR THE MANAGEMENT AND CONTROL OF THE ELECTRICAL POWER SUPPLY FOR RESISTANCE WELDING, IN PARTICULAR OF METAL BOX BODIES. |
| DE4331826C1 (en) * | 1993-09-18 | 1994-12-08 | Sibea Gmbh Ingenieurbetrieb Fu | Method of resistance welding thin sheet and arrangement for carrying out the method |
| EP0646433A1 (en) * | 1993-09-30 | 1995-04-05 | Siemens Aktiengesellschaft | Method, apparatus for high speed resistance welding of thin sheets |
| JPH081351A (en) * | 1994-06-21 | 1996-01-09 | Nasu Toa Kk | Method and device for invertor control type ac resistance welding |
| JP4426693B2 (en) * | 2000-03-22 | 2010-03-03 | ミヤチテクノス株式会社 | Metal member joining method and reflow soldering method |
| KR101289370B1 (en) * | 2008-09-30 | 2013-07-29 | 도쿠리츠교세이호징 붓시쯔 자이료 겐큐키코 | Welding device for metal and welding method for metal |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2004609B2 (en) * | 1970-02-02 | 1972-09-21 | Standard Elektrik Lorenz Ag, 7000 Stuttgart | DC VOLTAGE CONVERTER |
| DE2913627A1 (en) * | 1979-04-05 | 1980-10-16 | Messer Griesheim Gmbh | DEVICE FOR DC AND / OR AC ARC WELDING WITH AN INVERTER |
-
1981
- 1981-05-13 DE DE8181103674T patent/DE3172302D1/en not_active Expired
- 1981-05-13 EP EP81103674A patent/EP0064570B2/en not_active Expired - Lifetime
- 1981-05-13 AT AT81103674T patent/ATE15617T1/en not_active IP Right Cessation
-
1982
- 1982-05-04 ES ES511904A patent/ES511904A0/en active Granted
- 1982-05-08 BR BR8207698A patent/BR8207698A/en not_active IP Right Cessation
- 1982-05-08 JP JP57501535A patent/JPS58500702A/en active Granted
- 1982-05-08 WO PCT/DE1982/000097 patent/WO1982004000A1/en unknown
- 1982-05-12 CA CA000402770A patent/CA1183578A/en not_active Expired
-
1983
- 1983-01-12 DK DK010483A patent/DK159011C/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DK10483A (en) | 1983-01-12 |
| WO1982004000A1 (en) | 1982-11-25 |
| ATE15617T1 (en) | 1985-10-15 |
| DK159011C (en) | 1991-02-11 |
| ES8303957A1 (en) | 1983-02-16 |
| EP0064570B1 (en) | 1985-09-18 |
| DE3172302D1 (en) | 1985-10-24 |
| EP0064570B2 (en) | 1990-07-11 |
| JPS58500702A (en) | 1983-05-06 |
| EP0064570A1 (en) | 1982-11-17 |
| DK10483D0 (en) | 1983-01-12 |
| DK159011B (en) | 1990-08-20 |
| ES511904A0 (en) | 1983-02-16 |
| JPH0221917B2 (en) | 1990-05-16 |
| BR8207698A (en) | 1983-05-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1183578A (en) | Source of electrical energy for a resistance-welding machine | |
| JP2602778B2 (en) | High frequency power supply | |
| EP0688626B1 (en) | Control equipment for resistance welding machine | |
| ATE58451T1 (en) | METHOD AND DEVICE FOR CONTROLLING A THREE-PHASE MACHINE. | |
| JPH03118880A (en) | Power supply apparatus for driving a piezoelectric transducer | |
| JPH06234072A (en) | Inverter power supply for welding | |
| US4973815A (en) | Resistance welder using an inverter | |
| CN102107323B (en) | Resistance welding nugget quality control method | |
| US4414455A (en) | Method of and apparatus for producing can bodies welded along the longitudinal seam | |
| US3921058A (en) | Device for compensating AC power source voltage | |
| JP2599906B2 (en) | Power supply for seam welding | |
| US4935860A (en) | PWM inverter circuit having modulated DC link input | |
| EP0769221B1 (en) | Load-commutated synchronous motor drive | |
| US4677272A (en) | Seam welding machine | |
| US4654503A (en) | Welding current power supply with inductive clipping | |
| JPH0753313B2 (en) | Power control device for inverter type resistance welding machine | |
| CA1153063A (en) | Ac motor drive system having clamped command error signal | |
| CA1125390A (en) | Method and apparatus for controlling the welding capacity during electrical resistance welding | |
| EP0088277A3 (en) | Control device for a dc-ac converter and its use in a method and apparatus for the circulation of a heating fluid in a heating tube system | |
| US4621222A (en) | Method for improving the dynamic converter drive for a direct current elevator motor | |
| JPS581809B2 (en) | Smooth DC generator | |
| US4044223A (en) | Apparatus for pulsed arc welding and building-up of articles | |
| WO1986000035A1 (en) | Resistance welder | |
| JPH10277739A (en) | Power source for arc working | |
| JPS632707B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20020512 |