CA2080461A1 - Shunt coil controlled transformer - Google Patents
Shunt coil controlled transformerInfo
- Publication number
- CA2080461A1 CA2080461A1 CA002080461A CA2080461A CA2080461A1 CA 2080461 A1 CA2080461 A1 CA 2080461A1 CA 002080461 A CA002080461 A CA 002080461A CA 2080461 A CA2080461 A CA 2080461A CA 2080461 A1 CA2080461 A1 CA 2080461A1
- Authority
- CA
- Canada
- Prior art keywords
- shunt
- coil
- magnetic path
- transformer
- symmetry
- 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.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/12—Regulating voltage or current wherein the variable actually regulated by the final control device is ac
- G05F1/32—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using magnetic devices having a controllable degree of saturation as final control devices
- G05F1/325—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using magnetic devices having a controllable degree of saturation as final control devices with specific core structure, e.g. gap, aperture, slot, permanent magnet
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F38/00—Adaptations of transformers or inductances for specific applications or functions
- H01F38/08—High-leakage transformers or inductances
- H01F38/085—Welding transformers
-
- 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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/10—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers
- H02M5/12—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers for conversion of voltage or current amplitude only
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F29/00—Variable transformers or inductances not covered by group H01F21/00
- H01F29/14—Variable transformers or inductances not covered by group H01F21/00 with variable magnetic bias
- H01F2029/143—Variable transformers or inductances not covered by group H01F21/00 with variable magnetic bias with control winding for generating magnetic bias
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S174/00—Electricity: conductors and insulators
- Y10S174/13—High voltage cable, e.g. above 10kv, corona prevention
- Y10S174/14—High voltage cable, e.g. above 10kv, corona prevention having a particular cable application, e.g. winding
- Y10S174/17—High voltage cable, e.g. above 10kv, corona prevention having a particular cable application, e.g. winding in an electric power conversion, regulation, or protection system
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S174/00—Electricity: conductors and insulators
- Y10S174/13—High voltage cable, e.g. above 10kv, corona prevention
- Y10S174/14—High voltage cable, e.g. above 10kv, corona prevention having a particular cable application, e.g. winding
- Y10S174/24—High voltage cable, e.g. above 10kv, corona prevention having a particular cable application, e.g. winding in an inductive device, e.g. reactor, electromagnet
- Y10S174/25—Transformer
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Arc Welding Control (AREA)
Abstract
A transformer (100) having a shunt magnetic path (108A) and a shunt coil (108) is provided. The transformer (100) includes control circuitry to control the output of the transformer by controlling current flow in the shunt coil (108), thereby controlling the flux through the shunt magnetic path (108A) and the flux coupling with the secondary coil (106). The current in the shunt coil (108) is phase-controlled and power for the control circuitry is derived from the current induced in the shunt coil (108).
Description
WO92/15051 PCT~US92/01~
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BACKGROUND OF THE INVENTION
Techni~al Field ~
The present invention relates generally to `
t~ansformers and, in particular, to electronically controlled transformers used in AC or DC arc welding power supplies or other applications where it is desirable to control the output of a~transformer.
Backqround Art The prior art is replete with methods and devices to control the output of a transformer. Some such devices include the use of switches, such as thyristors, to contro} the phase of either the primary or secondary current, thereby controlling the transformer output. These devices offer a large control range and typically low power consumption by the control circuit.
However, the on/off nature of the control devices drastically disturbs the ou~pu~ waveform. This adversely affects the performance of devices such as welding machines making Such devices useful only for specific SUdSTlTUTESHEFT ~ ~
WO92/15051 2 Q ~ PCT/US92/01 applications. Moreover, when such a transformer is used in a welder or other high current application, the control circuitry must be capable of handling high current levels, thereby increasing the C05t of the equipment.
Other devices utilize a magnetic core as a shunt in the magnetic circuit to decouple the primary and secondary windings and thus control the output voltage of the transformer. Devices such as these control the flux shunted through t~e shunt core, thereby controlling the flux through the secondary core and the output of the transformer.
The flux shunted through the shunt core may be controlled by physically moving the shunt core in and out of the magnetic circuit. However, such a mechanical -~
control is not well suited for use with a remote con~rol.
Moreover, the forces on a shunt core are sufficient to cause a movable shunt core to vibrate and may create undesirably loud noise.
Another example of a shunt controlled transformer is shown in U. S. Patent No. 4,177,418 issued to Breuckner et al Dec. 4, 1979. Breuckner discloses a transformer having a two-legged shunt core and a coil wrapped around each leg. The shunt coils are electrically connec~ed in series, but with a reversed polarity, causing the AC current induced in the shunt coils to be in opposite directions and cancel. A switch in series with the shunt coils is opened and closed, selectively allowing DC current to flow through the shunt coils, thereby maintaining the output o~ the transformer ;~
within a predetermined range of a desired level.
The switch in the Breuckner arrangement is part of a control circuit having an independent source of DC
power. Moreover, the shunt coils, primary coil, and secondary coil~ are disclosed as being disposed parallel '' ' `:
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:
BACKGROUND OF THE INVENTION
Techni~al Field ~
The present invention relates generally to `
t~ansformers and, in particular, to electronically controlled transformers used in AC or DC arc welding power supplies or other applications where it is desirable to control the output of a~transformer.
Backqround Art The prior art is replete with methods and devices to control the output of a transformer. Some such devices include the use of switches, such as thyristors, to contro} the phase of either the primary or secondary current, thereby controlling the transformer output. These devices offer a large control range and typically low power consumption by the control circuit.
However, the on/off nature of the control devices drastically disturbs the ou~pu~ waveform. This adversely affects the performance of devices such as welding machines making Such devices useful only for specific SUdSTlTUTESHEFT ~ ~
WO92/15051 2 Q ~ PCT/US92/01 applications. Moreover, when such a transformer is used in a welder or other high current application, the control circuitry must be capable of handling high current levels, thereby increasing the C05t of the equipment.
Other devices utilize a magnetic core as a shunt in the magnetic circuit to decouple the primary and secondary windings and thus control the output voltage of the transformer. Devices such as these control the flux shunted through t~e shunt core, thereby controlling the flux through the secondary core and the output of the transformer.
The flux shunted through the shunt core may be controlled by physically moving the shunt core in and out of the magnetic circuit. However, such a mechanical -~
control is not well suited for use with a remote con~rol.
Moreover, the forces on a shunt core are sufficient to cause a movable shunt core to vibrate and may create undesirably loud noise.
Another example of a shunt controlled transformer is shown in U. S. Patent No. 4,177,418 issued to Breuckner et al Dec. 4, 1979. Breuckner discloses a transformer having a two-legged shunt core and a coil wrapped around each leg. The shunt coils are electrically connec~ed in series, but with a reversed polarity, causing the AC current induced in the shunt coils to be in opposite directions and cancel. A switch in series with the shunt coils is opened and closed, selectively allowing DC current to flow through the shunt coils, thereby maintaining the output o~ the transformer ;~
within a predetermined range of a desired level.
The switch in the Breuckner arrangement is part of a control circuit having an independent source of DC
power. Moreover, the shunt coils, primary coil, and secondary coil~ are disclosed as being disposed parallel '' ' `:
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to one another, thereby increasing the size of the -transformer. The shunt coils are also positioned in a plane other than the plane of the primary and secondary coils, further increasing the size of transformer.
Presently known control systems are unsatisfactory in several regards. ~he waveform of the output of the transformer is often undesirable because the output current goes to zero when the control system is regulating the output. Many require a separate reactor which is expensive, some require a physical construction that is undesirably large, others require expensive high current control components. Accordingly, the need exists for a simplified yet economically efficient electronically controlled transformer.
SUMMARY OF THE INVENTION
In one preferred form, the present invention is directed towards a transformer having a shunt magnetic path and a shunt coil inductively coupled to the shunt magnetic path. A switch, powered by the shunt coil, is coupled to the shunt coil.
According to a second embodiment a transformer comprises a shunt magnetic path and a shunt coil inductively coupled to the shunt magnetic path. A switch is provided for selectively contro~ling an output of the transformer by selectively controlling an AC waveform induced in the shunt coil.
According to a third embodiment a transformer comprises a shunt magnetic core and a shunt coil inductively coupled to the shunt magnetic core. A switch ~'A
for selectively controlling the magnitude of an output of the transformer by selectively controlling current flow through the shunt coil is provided. The switch comprises a magnitude sensor for sensing a magnitude difference between first and second input signals and for SUBSTITUTE SHEE~
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selectively controlling the switch. Power for the switch is derived from the magnitude sensor.
According to a fourth embodiment a method for controlling a transformer comprises the step of providing a shunt magnetic path and a shunt coil inductively coupled to the shunt magnetic path. The steps of providing a timing signal and selectively controlling an output of the transformer by controlling current flow through the shunt coil in response to the timing signal ~ ~
are also performed. ~, BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a magnetic core and the windings of a transformer constructed according to the present invention;
Figure 2 is a top plan view of a magnetic core of a transformer constructed according to the present invention;
Figures 3A and 3B are circuit diagrams of a preferred exemplary embodiment of a transformer made in accordance with the subject invention;
Figures 3C and 3D are circuit diagrams of a preferred exemplary embodiment of a transform~r used in a , welding application made in accordance with the subject invention;
Figure 4 is a schematic diagram of the switch shown in Figures 3C and 3D; and `
Figure 5 is a circuit~diagram of an alternative exemplary embodiment of a transformer made in accordance with the subject invention.
.-DETAILED DESCRIPTIQN OF A PREFERRED EXEMPLARY EMBODIMENT
The present invention is directed to the control of a transformer, such as one used to deliver controllable electric power to establish and maintain a S~i~STlrUT~ S~ff .
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welding arc. The illustrated transformer is constructed to provide an amplifying effect wherein changes in a relatively high output current are effected by controlling a relatively low shunt current.
Referring to Figure 1, a transformer, designated generally as 100, constructed in accordance with the present invention includes a magnetic core 102, a primary coil 104, a secondary coil 106, and a shunt coil 108. Flux coupling with primary coil 104 follows a primary magnetic path 104A, flux coupling with secondary coil 106 follows a secondary magnetic path 106A, and flux ;~
coupling with shunt coil 108 follows a shunt magnetic path 108A. Primary magnetic path 104A and secondary -~
magnetic path 106A together form the main magnetic path of transformer 100.
Shunt coil 108 is provided to allow the output of transformer 100 to be controlled electronically. More particularly, according to one method of the present invention the high current output of transformer 100 is used in a welding application and is controlled by controlling the induced AC current in shunt coil 108. ;~
When shunt coil 108 is open-circuited, no induced AC current will flow in shunt coil 108 and a relatively large portion of the flux generated by primary ~k coil 104 is shunted along shunt magnetic path 108A, reducing the flux in secondary magnetic path 106A. In other words, coupling between primary coil 104 and secondary coil 106 is poor because of the flux shunted along shunt magnetic path 108A.
However, when shunt coil 108 is close-circuited, the flux generated by primary coil 104 induces an AC current in shunt coil 108. The induced current produces a magneto-motive ~orce ("MMF"~, which tends to unbalance the flux componen~is in magnetic core 102. This 3~ causes primary coil 104 to attempt to draw additional SUBSTl'rUTEâ~' ;. ~.
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current to create addltional flux sufficient to rebalance the flux and the MMF in magnetic core 102. ;
The additional flux increases the output of transformer 100 because it is divided between shunt magnetic path 108A and secondary magnetic path 106~. As will be discussed in detail below, the ratio of the flux in secondary magnetic path 106~ to the flux in shunt magnetic path 108~, ~S~/tshU~t, is equal. to the ratio of the reluctance of shunt magnetic path 108A to the reluctance of seccndary magnetic path 106A, RshUn~/R
Transformer 100 is designed such that R5hUnt is much greater than RSec~ therefore most of the additional flux follows secondary magnetic path 106A, coupling with ~-secondary coil 106 and increasing the output of transformer 100. Thus, relatively small changes in ~shunt effect relatively large changes in ~s~ and the output of ~-transformer 100, and transformer 100 exhibits an amplifying effect with a gain of approximately ~ec/~shunt.
In summary, the magnitude of the output of transformer 100 is dependent on the amount of flux following secondary magnetic path 106A. The amount of flux following secondary magnetic path 106A is in turn responsive to the current flow through shunt coil 108. ~;~
Thus, the output of transformer 100 may be controlled by controlling the current flow through shunt coil 108.
In the preferred embodiment control of the output is achieved by open-circuiting and close-circuiting shunt coil 108 for such times that the desired output is achieved. More particularly, shunt coil 108 is open-circuited at a first selected time in each AC cycle and close-circuited at a second selected time in eac~ AC
cycle. Thus, to increase the output of transformer 100 the length of time shunt coil 108 is close-circuited is increased, and to decrease the output of transformer 100 s~l~sr 7~rE ~
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the length of time shunt coil 108 is open-circuited is increased, in either case by adjusting the time at which switching occurs.
In accordance with another aspect of the present invention magnetic core 102 is comprised of a stack of magnetic "I" laminations, collectively and individually referred to as 110, and a stack of magnetic "E" laminations, collectively and individually referred to as 112, the latter having a shunt leg 114. Lamination stacks 110 and 117 are constructed by laminating magnetic plates together in accordance with conventional techniques and consist of any standard magnetic material.
The magnetic material should be selected consistent with the concentration of magnetic flux lines and reasonable 1~ losses due to cycling of the magnetic domains within the material. Alternatively, magnetic core 102 could be comprised of a ferrite material.
The construction shown in the preferred ~;
embodiment of Figure 1 was selected in order to have primary coil 104 and secondary coil 106 in close proximity to one another. The closeness of this proximity is a determining factor of the maximum output of the transformer. It is obvious to one skilled in the art that other arrangements are possible and more desirable for other applications.
The number of turns and the size of the wire comprising coils 104, 106 and 108 is arrived at using conventional techniques. By way of example, in the embodiment shown, which is intended to be used with a primary voltage of 230 volts at 60 Hz, primary coil 10~
is comprised of approximately 130 turns of number 8 AWG
(American Wire Gauge) wire, secondary coil 106 is comprised of approximately 30 turns of number 4 AWG wire, and shunt coil 108 is comprised of approximately 250 turns of number 10 AWG wire. Primary coil 104 and ;:.... ~ . -: : . :
WO92/15051 PCT/US92/0l4 secondary coil 106 are wound on "I" lamination stack 110 such that they have a common axis of symmetry Shunt ~ -coil 108, which is substantially coplanar with primary coil 104 and secondary coil 106, is wourld about shunt leg 114 such that its axis of symmetry is perpendicular to the axis of symmetry shared by primary c:oil 104 and secondary coil 106. Shunt leg 114 is positioned such that the axis of symmetry of shunt coil 108 is about ;~-equidistant primary coil 104 and secondary coil 106.
In the embodiment shown "I" lamination stack 110 and "E" lamination stack 112 are suitably comprised ~ ~
of 140 24 gauge electrical steel I and E laminations, ~ -respectively, each stack having a height of about 3.5 inches. Referring now to Figure 2, each "I" lamination ~ ~
110 has a length of about 8.0 inches and a width of about ~ ;
1.75 inches. Each "E" lamination 112 includes a pair of side legs 202 and 204, a base 206 and shunt leg 114.
Legs 202 and 204, suitably about 5.8 inches long and about 1.75 inches wide are positioned perpendicular to and against "I" lamination stack 110. Base 206 is~`~
approximately 8.0 inches in length, about 1.75 inches wide, and substantially perpendicular to legs 114, 202 and 204. Leg 114 is about 1.2 inches wide and about 4.02 inches long, so as to form an air gap 208 between it and "I" lamlnation stack 110. In the preferred exemplary embodiment air gap 208 is about 0.030 inches in length. ~-Alternatively, air gap 208 could be formed by providing a notch in "I" lamination 110.
As will be explained below, air gap 208, in conjunction with the physical dimensions of magnetic core 102, determines the gain of the amplifier effect, thereby determining the minimum and maximum output current of transformer lO0.
As stated above, the magnitudes of the magnetic reluctances of secondary magnetic path 106A and shunt S~S I ITUTE SHEET
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magnetic path 108A determines the relative flux in each path and, therefore, the gain of the amplifier effect.
The primary flux, ~pri~ produced by the current in primary coil 104 follows either secondary magnetic path ~06A or shunt magnetic path 108A such that ~p~ ~ ~s~ + ~shunt.
Because the MMF, which is ~ * R, across two parallel branches of a magnetic circuit must be e~qual, the MMF of secondary ma~netic path 106A and shunt n~agnetic path 108A
must be equal (~sec * ~sec = ~shunt Rshunt)~ and the relative flux in each path is inversely proportional to ;~
the reluctance. Thus, the gain of the amplifier effect, ecl~shunt~ is equal to R5hunt/R
To obtain the desired gain, the reluctances of -~;
secondary magnetic path 106A and shunt magnetic path 108A
are tailored by properly selecting their respective cross sectional areas, lengths, and effective permeabilities.
RseC~ the reluctance of secondary magnetic path 106A, is g n by lSeC / (~sec * a5~)~ where ~sec is the permeability of the material in secondary magnetic path 106A, and 15eC and ASec are the mean length and cross sectional area of secondary magnetic path 106A, ~ ;
respectively. Similarly, R5hUnt~ the reluctance of shunt magnetic path 108A, including air gap 208, is given by ~lshunt / ~shunt*Ashunt)) + 51gap / ~o~Aeffl) where lShUnt is the mean length o~ shunt magnetic path 108A less the length of air gap 208, ~shu~t is the permeability of the `
material in the shunt portion of the magnetic circuit, AShunt is the area of shunt leg 114, lgap is the length of air gap 208, ~0 is the permeability of air, and Aef~ is ~0 the effective area of air gap 208. Because Aeffl which may be approximated by adding the lgap to the dimensions defining AShUnt~ is approximately equal to ~shunt and ~ is a constant much less than ~shunt~ Rshunt is pr ~, S~IT~TE sttET
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determined by lgap~ Thus, by appropriately choosing the length of air gap 208, a desired value of RShunt may conveniently be obtained and, for a given R~, a desired magnetic gain may also be conveniently obtained. Of course, air gap 208 could be filled with any material having a reluctance greater than the reluctance of ;~
magnetic core 102. The size of air gap 208, and other physical characteristics of transformer 100l are chosen to provide reluctances in the secondary and shunt paths having a desirable ratio for the purpose of obtaining an output current range of 30 to 180 amps at an output voltage of up to 80 volts and having an acceptable waveform.
The ratio of the shunt reluctance to the secondary reluctance may be tailored to suit a particular application. For example, in the preferred embodiment, described herein which is intended to be used in an arc welding application, the ratio of the shunt reluctance to the secondary reluctance is approximately seven to one.
Referring now to Figures 3A and 3B, an AC power source 302 and a load 304 are shown in addition to ~`
transformer 100 which includes, as well, a switch circuit 306 having terminals 308 and 312. AC power source 302 is connected to primary coil 104 and load 304 is connected to secondary coil 106 in a conventional manner.
Switch circuit 306 controls the output current of transformer 100 by selectively open-circuiting and close-circuiting shunt coil 108. Specifically, a low ;
resistance current path between terminal 308 and terminal 312 is closed at a first selected time in each AC cycle of the waveform induced in shunt coil 108 and opened at a second selected time in each AC cycle of the waveform induced in shunt coil 108. Preferably, the current path between 308 and 312 is an extremely low resistance path 3~ when close circuited. Regardless, the time at which the ~JesTlT~lTES~
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WO92/15051 ~ L~ P~T/US~2/01 curre~lt path is opened and closed de~ermines the current flow in shunt coil 10~ and, therefore, the output of transformer 100. The output of transformer 100 is increased by moving the first selected time earlier or moving the second selected time later with respect to the zero crossing of AC voltage induced in the shunt coil 108. Likewise, ~he output of transformer 100 is decreased by moving the first selected time later or moving the second selected time earlier. As those well -skilled in the art will recognize, switch circuit 306 may instead be responsive to other signals such as the waveform on primary coil 104 or an independently generated timing signal, and any timing device that .
provides a duty cycle may be used to trigger the 1~ switching of switch circuit 306.
Alternatively, switch circuit 3Q6 may be responsive to the magnitude of an input signal. Because of the periodic nature of the AC waveform induced on shunt coil 108, respon~ing to the magnitude of the voltage induced on shunt coil 108 will result in switching at a given time in each AC cycle, thereby selecting the relative open and close circuited times.
Referring now to ~i~ures 3C and 3D, an embodiment of the present invention particularly well ~-suited for arc welding applications is shown. A phase control swi~ch 306A (described in detail below with reference to Figure 4) includes terminals 308A, 310A and 312A. A current path between terminals 308A and 312A is closed at a predetermined time relative to each zero crossing of the AC waveform applied to terminais 308A and 310A. The current path is opened at each zero crossing of the AC waveform applied to terminals 308A and 310A.
The current induced in shunt coil 108 is circulated through load 304, thereby increasing the output power of 3~ the transformer. Also, because the current in shunt coil SUB~TITIJTE S~
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104 is slightly out of phase with respect to the current in secondary coil 106, the shunt current may be added to the rectified output of the transformer by means of a unidirectional switching device, adding to the stability of the welding arc.
~eferring now to Figure 4, phase control switch 306A provides a virtual short circuit between terminals ~;
308A and 312A at a predetermined time relative to each zero crosslng of the waveform applied to terminals 308A
and 310A. Specif~cally, a bi-directional thyristor 402, provided between terminals 308A and 312A, is caused to conduct at a predetermined time in each half cycle of the AC waveform applied to terminals 308A and 310A.
Thyristor 402 will continue to conduct until it becomes reverse-biased when the polarity across terminals 308A
and 310A reverses. Because the waveform applied to terminals 308A and 310A is periodic, the time at which thyristor 402 begins cor~ducting relative to each zero crossing determines the relative "on" time and "of~" time of current flow through shunt coil 108. As stated above, the relative "on" time and "off" time of current flow through shunt coil 108 controls the flux through secondary magnetic path 106A and, therefore, the output ~ -of transformer 100.
In the embodiment shown in Figure 4 the predetermined time in each AC cycle at which thyristor 402 begins conducting is controlled by adjusting the resistance of a variable resistor 408. A capacitor 412 is charged by the voltage difference between terminals 308A and 310A, ~hrough variable resistor 408 and a resistor 404. When the voltage on capacitor 412 becomes greater than the triggering threshold of a trigger 410, it sends a timing signal to a resistor 406 and thyristor 402, thereby causing thyristor 402 to conduct. The 3~ charging time of capacitor 4 12, and the time at which :.
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WO92/15051 ~ ~ S ~ PCTtUS92/01 thyristor 402 be lns conducting, is dependent upon the RC
tlme constant of resistor 404, variable resistor 408 and capacitor 412. Thus, by adjusting the resistance of variable resistor 408 the RC time constant may be adjusted, thereby controlling the length of time that thyristor 402 conducts and, therPfore, the output of transformer 100.
Phase control switch 3Q6A is designed to eliminate the need for an independent source of power or lo reference voltage. The power to turn phase control switch 306A on and off is obtained directly from the voltage induced on shunt coil 108 and no reference voltage is needed because trigger 410 operates ~ the energy stored in capacitor 412.
The present lvention is suitable for welding ;
applications which re~lre a balanced output waveform as well as welding applications which require an unbalanced output waveform, such as TIG welding. A balancecl output waveform is obtained by allowing thyristor 402 to conduct on both the positive and negative half-cycles of the voltage induced on shunt coil 108 and an unbalanced output waveform is provided by allowing thyristor 402 to conduct on only the positive or negative half-cycle. ~ ;
Selection between balanced and unbalanced output waveforms may be made using a selector switch 414, having terminals 416-422. When terminal 416 is connected to terminal 420, capacitor 412 is charged on both the positive and negative halves o~the waveform, and thyristor 402 conducts on both positive and negative halves of the waveform. However, when terminal 416 is connected to terminal 422, capacitor 412 is short-circuited by a diode 426 on the negative half of the waveform and charges on only the positive half of the waveform. Similarly, when terminal 416 is connected to terminal 418 capacitor 412 is short-circuited by a diode SUBSrlTUT~ SHEEl . ~- : :~ -. . ^. . . , - . -,: . :
W~92/15051 PCT/US92/01~ ~
2~
424 on the positive half of the waveform and charges on only the negative half of the waveform.
Phase control switch 306A may be connected ln alternative arrangements, such as that shown in Figure 5.
Referring to Figure 5, shunt coil 108 and primary coil 104 are connected in series when phase control switch 306A is off. When phase control switch is triggered on, by the waveform on shunt coil 108, the current in primary coil 104 bypasses shunt coil 108, and the current in shunt coil 108 bypasses primary coil 10~.
Other modifications may be made in the design and arrangement of the elements discussed herein without . . .
departing from the spirit and scope of the invention, as expressed in the appended claims.
SUBSTITUTESHEET :: ~
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to one another, thereby increasing the size of the -transformer. The shunt coils are also positioned in a plane other than the plane of the primary and secondary coils, further increasing the size of transformer.
Presently known control systems are unsatisfactory in several regards. ~he waveform of the output of the transformer is often undesirable because the output current goes to zero when the control system is regulating the output. Many require a separate reactor which is expensive, some require a physical construction that is undesirably large, others require expensive high current control components. Accordingly, the need exists for a simplified yet economically efficient electronically controlled transformer.
SUMMARY OF THE INVENTION
In one preferred form, the present invention is directed towards a transformer having a shunt magnetic path and a shunt coil inductively coupled to the shunt magnetic path. A switch, powered by the shunt coil, is coupled to the shunt coil.
According to a second embodiment a transformer comprises a shunt magnetic path and a shunt coil inductively coupled to the shunt magnetic path. A switch is provided for selectively contro~ling an output of the transformer by selectively controlling an AC waveform induced in the shunt coil.
According to a third embodiment a transformer comprises a shunt magnetic core and a shunt coil inductively coupled to the shunt magnetic core. A switch ~'A
for selectively controlling the magnitude of an output of the transformer by selectively controlling current flow through the shunt coil is provided. The switch comprises a magnitude sensor for sensing a magnitude difference between first and second input signals and for SUBSTITUTE SHEE~
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selectively controlling the switch. Power for the switch is derived from the magnitude sensor.
According to a fourth embodiment a method for controlling a transformer comprises the step of providing a shunt magnetic path and a shunt coil inductively coupled to the shunt magnetic path. The steps of providing a timing signal and selectively controlling an output of the transformer by controlling current flow through the shunt coil in response to the timing signal ~ ~
are also performed. ~, BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a magnetic core and the windings of a transformer constructed according to the present invention;
Figure 2 is a top plan view of a magnetic core of a transformer constructed according to the present invention;
Figures 3A and 3B are circuit diagrams of a preferred exemplary embodiment of a transformer made in accordance with the subject invention;
Figures 3C and 3D are circuit diagrams of a preferred exemplary embodiment of a transform~r used in a , welding application made in accordance with the subject invention;
Figure 4 is a schematic diagram of the switch shown in Figures 3C and 3D; and `
Figure 5 is a circuit~diagram of an alternative exemplary embodiment of a transformer made in accordance with the subject invention.
.-DETAILED DESCRIPTIQN OF A PREFERRED EXEMPLARY EMBODIMENT
The present invention is directed to the control of a transformer, such as one used to deliver controllable electric power to establish and maintain a S~i~STlrUT~ S~ff .
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welding arc. The illustrated transformer is constructed to provide an amplifying effect wherein changes in a relatively high output current are effected by controlling a relatively low shunt current.
Referring to Figure 1, a transformer, designated generally as 100, constructed in accordance with the present invention includes a magnetic core 102, a primary coil 104, a secondary coil 106, and a shunt coil 108. Flux coupling with primary coil 104 follows a primary magnetic path 104A, flux coupling with secondary coil 106 follows a secondary magnetic path 106A, and flux ;~
coupling with shunt coil 108 follows a shunt magnetic path 108A. Primary magnetic path 104A and secondary -~
magnetic path 106A together form the main magnetic path of transformer 100.
Shunt coil 108 is provided to allow the output of transformer 100 to be controlled electronically. More particularly, according to one method of the present invention the high current output of transformer 100 is used in a welding application and is controlled by controlling the induced AC current in shunt coil 108. ;~
When shunt coil 108 is open-circuited, no induced AC current will flow in shunt coil 108 and a relatively large portion of the flux generated by primary ~k coil 104 is shunted along shunt magnetic path 108A, reducing the flux in secondary magnetic path 106A. In other words, coupling between primary coil 104 and secondary coil 106 is poor because of the flux shunted along shunt magnetic path 108A.
However, when shunt coil 108 is close-circuited, the flux generated by primary coil 104 induces an AC current in shunt coil 108. The induced current produces a magneto-motive ~orce ("MMF"~, which tends to unbalance the flux componen~is in magnetic core 102. This 3~ causes primary coil 104 to attempt to draw additional SUBSTl'rUTEâ~' ;. ~.
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current to create addltional flux sufficient to rebalance the flux and the MMF in magnetic core 102. ;
The additional flux increases the output of transformer 100 because it is divided between shunt magnetic path 108A and secondary magnetic path 106~. As will be discussed in detail below, the ratio of the flux in secondary magnetic path 106~ to the flux in shunt magnetic path 108~, ~S~/tshU~t, is equal. to the ratio of the reluctance of shunt magnetic path 108A to the reluctance of seccndary magnetic path 106A, RshUn~/R
Transformer 100 is designed such that R5hUnt is much greater than RSec~ therefore most of the additional flux follows secondary magnetic path 106A, coupling with ~-secondary coil 106 and increasing the output of transformer 100. Thus, relatively small changes in ~shunt effect relatively large changes in ~s~ and the output of ~-transformer 100, and transformer 100 exhibits an amplifying effect with a gain of approximately ~ec/~shunt.
In summary, the magnitude of the output of transformer 100 is dependent on the amount of flux following secondary magnetic path 106A. The amount of flux following secondary magnetic path 106A is in turn responsive to the current flow through shunt coil 108. ~;~
Thus, the output of transformer 100 may be controlled by controlling the current flow through shunt coil 108.
In the preferred embodiment control of the output is achieved by open-circuiting and close-circuiting shunt coil 108 for such times that the desired output is achieved. More particularly, shunt coil 108 is open-circuited at a first selected time in each AC cycle and close-circuited at a second selected time in eac~ AC
cycle. Thus, to increase the output of transformer 100 the length of time shunt coil 108 is close-circuited is increased, and to decrease the output of transformer 100 s~l~sr 7~rE ~
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the length of time shunt coil 108 is open-circuited is increased, in either case by adjusting the time at which switching occurs.
In accordance with another aspect of the present invention magnetic core 102 is comprised of a stack of magnetic "I" laminations, collectively and individually referred to as 110, and a stack of magnetic "E" laminations, collectively and individually referred to as 112, the latter having a shunt leg 114. Lamination stacks 110 and 117 are constructed by laminating magnetic plates together in accordance with conventional techniques and consist of any standard magnetic material.
The magnetic material should be selected consistent with the concentration of magnetic flux lines and reasonable 1~ losses due to cycling of the magnetic domains within the material. Alternatively, magnetic core 102 could be comprised of a ferrite material.
The construction shown in the preferred ~;
embodiment of Figure 1 was selected in order to have primary coil 104 and secondary coil 106 in close proximity to one another. The closeness of this proximity is a determining factor of the maximum output of the transformer. It is obvious to one skilled in the art that other arrangements are possible and more desirable for other applications.
The number of turns and the size of the wire comprising coils 104, 106 and 108 is arrived at using conventional techniques. By way of example, in the embodiment shown, which is intended to be used with a primary voltage of 230 volts at 60 Hz, primary coil 10~
is comprised of approximately 130 turns of number 8 AWG
(American Wire Gauge) wire, secondary coil 106 is comprised of approximately 30 turns of number 4 AWG wire, and shunt coil 108 is comprised of approximately 250 turns of number 10 AWG wire. Primary coil 104 and ;:.... ~ . -: : . :
WO92/15051 PCT/US92/0l4 secondary coil 106 are wound on "I" lamination stack 110 such that they have a common axis of symmetry Shunt ~ -coil 108, which is substantially coplanar with primary coil 104 and secondary coil 106, is wourld about shunt leg 114 such that its axis of symmetry is perpendicular to the axis of symmetry shared by primary c:oil 104 and secondary coil 106. Shunt leg 114 is positioned such that the axis of symmetry of shunt coil 108 is about ;~-equidistant primary coil 104 and secondary coil 106.
In the embodiment shown "I" lamination stack 110 and "E" lamination stack 112 are suitably comprised ~ ~
of 140 24 gauge electrical steel I and E laminations, ~ -respectively, each stack having a height of about 3.5 inches. Referring now to Figure 2, each "I" lamination ~ ~
110 has a length of about 8.0 inches and a width of about ~ ;
1.75 inches. Each "E" lamination 112 includes a pair of side legs 202 and 204, a base 206 and shunt leg 114.
Legs 202 and 204, suitably about 5.8 inches long and about 1.75 inches wide are positioned perpendicular to and against "I" lamination stack 110. Base 206 is~`~
approximately 8.0 inches in length, about 1.75 inches wide, and substantially perpendicular to legs 114, 202 and 204. Leg 114 is about 1.2 inches wide and about 4.02 inches long, so as to form an air gap 208 between it and "I" lamlnation stack 110. In the preferred exemplary embodiment air gap 208 is about 0.030 inches in length. ~-Alternatively, air gap 208 could be formed by providing a notch in "I" lamination 110.
As will be explained below, air gap 208, in conjunction with the physical dimensions of magnetic core 102, determines the gain of the amplifier effect, thereby determining the minimum and maximum output current of transformer lO0.
As stated above, the magnitudes of the magnetic reluctances of secondary magnetic path 106A and shunt S~S I ITUTE SHEET
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magnetic path 108A determines the relative flux in each path and, therefore, the gain of the amplifier effect.
The primary flux, ~pri~ produced by the current in primary coil 104 follows either secondary magnetic path ~06A or shunt magnetic path 108A such that ~p~ ~ ~s~ + ~shunt.
Because the MMF, which is ~ * R, across two parallel branches of a magnetic circuit must be e~qual, the MMF of secondary ma~netic path 106A and shunt n~agnetic path 108A
must be equal (~sec * ~sec = ~shunt Rshunt)~ and the relative flux in each path is inversely proportional to ;~
the reluctance. Thus, the gain of the amplifier effect, ecl~shunt~ is equal to R5hunt/R
To obtain the desired gain, the reluctances of -~;
secondary magnetic path 106A and shunt magnetic path 108A
are tailored by properly selecting their respective cross sectional areas, lengths, and effective permeabilities.
RseC~ the reluctance of secondary magnetic path 106A, is g n by lSeC / (~sec * a5~)~ where ~sec is the permeability of the material in secondary magnetic path 106A, and 15eC and ASec are the mean length and cross sectional area of secondary magnetic path 106A, ~ ;
respectively. Similarly, R5hUnt~ the reluctance of shunt magnetic path 108A, including air gap 208, is given by ~lshunt / ~shunt*Ashunt)) + 51gap / ~o~Aeffl) where lShUnt is the mean length o~ shunt magnetic path 108A less the length of air gap 208, ~shu~t is the permeability of the `
material in the shunt portion of the magnetic circuit, AShunt is the area of shunt leg 114, lgap is the length of air gap 208, ~0 is the permeability of air, and Aef~ is ~0 the effective area of air gap 208. Because Aeffl which may be approximated by adding the lgap to the dimensions defining AShUnt~ is approximately equal to ~shunt and ~ is a constant much less than ~shunt~ Rshunt is pr ~, S~IT~TE sttET
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determined by lgap~ Thus, by appropriately choosing the length of air gap 208, a desired value of RShunt may conveniently be obtained and, for a given R~, a desired magnetic gain may also be conveniently obtained. Of course, air gap 208 could be filled with any material having a reluctance greater than the reluctance of ;~
magnetic core 102. The size of air gap 208, and other physical characteristics of transformer 100l are chosen to provide reluctances in the secondary and shunt paths having a desirable ratio for the purpose of obtaining an output current range of 30 to 180 amps at an output voltage of up to 80 volts and having an acceptable waveform.
The ratio of the shunt reluctance to the secondary reluctance may be tailored to suit a particular application. For example, in the preferred embodiment, described herein which is intended to be used in an arc welding application, the ratio of the shunt reluctance to the secondary reluctance is approximately seven to one.
Referring now to Figures 3A and 3B, an AC power source 302 and a load 304 are shown in addition to ~`
transformer 100 which includes, as well, a switch circuit 306 having terminals 308 and 312. AC power source 302 is connected to primary coil 104 and load 304 is connected to secondary coil 106 in a conventional manner.
Switch circuit 306 controls the output current of transformer 100 by selectively open-circuiting and close-circuiting shunt coil 108. Specifically, a low ;
resistance current path between terminal 308 and terminal 312 is closed at a first selected time in each AC cycle of the waveform induced in shunt coil 108 and opened at a second selected time in each AC cycle of the waveform induced in shunt coil 108. Preferably, the current path between 308 and 312 is an extremely low resistance path 3~ when close circuited. Regardless, the time at which the ~JesTlT~lTES~
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WO92/15051 ~ L~ P~T/US~2/01 curre~lt path is opened and closed de~ermines the current flow in shunt coil 10~ and, therefore, the output of transformer 100. The output of transformer 100 is increased by moving the first selected time earlier or moving the second selected time later with respect to the zero crossing of AC voltage induced in the shunt coil 108. Likewise, ~he output of transformer 100 is decreased by moving the first selected time later or moving the second selected time earlier. As those well -skilled in the art will recognize, switch circuit 306 may instead be responsive to other signals such as the waveform on primary coil 104 or an independently generated timing signal, and any timing device that .
provides a duty cycle may be used to trigger the 1~ switching of switch circuit 306.
Alternatively, switch circuit 3Q6 may be responsive to the magnitude of an input signal. Because of the periodic nature of the AC waveform induced on shunt coil 108, respon~ing to the magnitude of the voltage induced on shunt coil 108 will result in switching at a given time in each AC cycle, thereby selecting the relative open and close circuited times.
Referring now to ~i~ures 3C and 3D, an embodiment of the present invention particularly well ~-suited for arc welding applications is shown. A phase control swi~ch 306A (described in detail below with reference to Figure 4) includes terminals 308A, 310A and 312A. A current path between terminals 308A and 312A is closed at a predetermined time relative to each zero crossing of the AC waveform applied to terminais 308A and 310A. The current path is opened at each zero crossing of the AC waveform applied to terminals 308A and 310A.
The current induced in shunt coil 108 is circulated through load 304, thereby increasing the output power of 3~ the transformer. Also, because the current in shunt coil SUB~TITIJTE S~
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104 is slightly out of phase with respect to the current in secondary coil 106, the shunt current may be added to the rectified output of the transformer by means of a unidirectional switching device, adding to the stability of the welding arc.
~eferring now to Figure 4, phase control switch 306A provides a virtual short circuit between terminals ~;
308A and 312A at a predetermined time relative to each zero crosslng of the waveform applied to terminals 308A
and 310A. Specif~cally, a bi-directional thyristor 402, provided between terminals 308A and 312A, is caused to conduct at a predetermined time in each half cycle of the AC waveform applied to terminals 308A and 310A.
Thyristor 402 will continue to conduct until it becomes reverse-biased when the polarity across terminals 308A
and 310A reverses. Because the waveform applied to terminals 308A and 310A is periodic, the time at which thyristor 402 begins cor~ducting relative to each zero crossing determines the relative "on" time and "of~" time of current flow through shunt coil 108. As stated above, the relative "on" time and "off" time of current flow through shunt coil 108 controls the flux through secondary magnetic path 106A and, therefore, the output ~ -of transformer 100.
In the embodiment shown in Figure 4 the predetermined time in each AC cycle at which thyristor 402 begins conducting is controlled by adjusting the resistance of a variable resistor 408. A capacitor 412 is charged by the voltage difference between terminals 308A and 310A, ~hrough variable resistor 408 and a resistor 404. When the voltage on capacitor 412 becomes greater than the triggering threshold of a trigger 410, it sends a timing signal to a resistor 406 and thyristor 402, thereby causing thyristor 402 to conduct. The 3~ charging time of capacitor 4 12, and the time at which :.
Sll~SnTlJT~ S~E-~
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WO92/15051 ~ ~ S ~ PCTtUS92/01 thyristor 402 be lns conducting, is dependent upon the RC
tlme constant of resistor 404, variable resistor 408 and capacitor 412. Thus, by adjusting the resistance of variable resistor 408 the RC time constant may be adjusted, thereby controlling the length of time that thyristor 402 conducts and, therPfore, the output of transformer 100.
Phase control switch 3Q6A is designed to eliminate the need for an independent source of power or lo reference voltage. The power to turn phase control switch 306A on and off is obtained directly from the voltage induced on shunt coil 108 and no reference voltage is needed because trigger 410 operates ~ the energy stored in capacitor 412.
The present lvention is suitable for welding ;
applications which re~lre a balanced output waveform as well as welding applications which require an unbalanced output waveform, such as TIG welding. A balancecl output waveform is obtained by allowing thyristor 402 to conduct on both the positive and negative half-cycles of the voltage induced on shunt coil 108 and an unbalanced output waveform is provided by allowing thyristor 402 to conduct on only the positive or negative half-cycle. ~ ;
Selection between balanced and unbalanced output waveforms may be made using a selector switch 414, having terminals 416-422. When terminal 416 is connected to terminal 420, capacitor 412 is charged on both the positive and negative halves o~the waveform, and thyristor 402 conducts on both positive and negative halves of the waveform. However, when terminal 416 is connected to terminal 422, capacitor 412 is short-circuited by a diode 426 on the negative half of the waveform and charges on only the positive half of the waveform. Similarly, when terminal 416 is connected to terminal 418 capacitor 412 is short-circuited by a diode SUBSrlTUT~ SHEEl . ~- : :~ -. . ^. . . , - . -,: . :
W~92/15051 PCT/US92/01~ ~
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424 on the positive half of the waveform and charges on only the negative half of the waveform.
Phase control switch 306A may be connected ln alternative arrangements, such as that shown in Figure 5.
Referring to Figure 5, shunt coil 108 and primary coil 104 are connected in series when phase control switch 306A is off. When phase control switch is triggered on, by the waveform on shunt coil 108, the current in primary coil 104 bypasses shunt coil 108, and the current in shunt coil 108 bypasses primary coil 10~.
Other modifications may be made in the design and arrangement of the elements discussed herein without . . .
departing from the spirit and scope of the invention, as expressed in the appended claims.
SUBSTITUTESHEET :: ~
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Claims (14)
1. A controllable transformer comprising:
a main magnetic path, said main magnetic path including a secondary magnetic path;
a shunt magnetic path in parallel with said secondary magnetic path of said shunt magnetic path having a reluctance greater than said;
a shunt coil inductively coupled to said shunt magnetic path; and switch means operatively associated with said shunt coil for selectively controlling an output of the transformer by selectively controlling an AC
waveform induced in said shunt coil.
a main magnetic path, said main magnetic path including a secondary magnetic path;
a shunt magnetic path in parallel with said secondary magnetic path of said shunt magnetic path having a reluctance greater than said;
a shunt coil inductively coupled to said shunt magnetic path; and switch means operatively associated with said shunt coil for selectively controlling an output of the transformer by selectively controlling an AC
waveform induced in said shunt coil.
2. The controllable transformer of claim 1 wherein said shunt magnetic path includes an air gap.
3. The controllable transformer of claim 1 further comprising a main magnetic path including a secondary magnetic path, wherein said secondary magnetic path has a reluctance less than the reluctance of said shunt path.
4. The controllable transformer of claim 1 wherein said switch means includes a timing means for selectively controlling said switch means.
5. The controllable transformer of claim 1 wherein said switch means includes a phase control means for selectively controlling said switch means.
6. The controllable transformer of claim 1 wherein the transformer includes a primary coil, a secondary coil and further wherein said shunt path is about equidistant from said primary coil and said secondary coil.
7. A controllable transformer comprising:
a secondary magnetic core;
a shunt magnetic core in parallel secondary magnetic core;
a shunt coil inductively coupled to said shunt magnetic core; and switch means for selectively controlling the magnitude of an output of the transformer by selectively controlling current flow through said shunt coil;
wherein said switch means comprises magnitude sensing means for sensing a magnitude difference between a first input signal applied to a first terminal and a second input signal applied to a second terminal and for selectively controlling the resistance of said switch means, and further wherein power for said switch means is derived from said magnitude sensing means.
a secondary magnetic core;
a shunt magnetic core in parallel secondary magnetic core;
a shunt coil inductively coupled to said shunt magnetic core; and switch means for selectively controlling the magnitude of an output of the transformer by selectively controlling current flow through said shunt coil;
wherein said switch means comprises magnitude sensing means for sensing a magnitude difference between a first input signal applied to a first terminal and a second input signal applied to a second terminal and for selectively controlling the resistance of said switch means, and further wherein power for said switch means is derived from said magnitude sensing means.
8. The controllable transformer of claim 7 further comprising a main magnetic core wherein a high reluctance path separates said shunt magnetic core and said main magnetic core.
9. The transformer of claim 8 further comprising:
a primary coil inductively coupled to said main magnetic core, said primary coil having a first axis of symmetry; and a secondary coil inductively coupled to said main magnetic core, said secondary coil having a second axis of symmetry, said first and second axes being generally collinear;
wherein said shunt coil comprises a shunt axis of symmetry disposed generally perpendicular to said first axis of symmetry.
a primary coil inductively coupled to said main magnetic core, said primary coil having a first axis of symmetry; and a secondary coil inductively coupled to said main magnetic core, said secondary coil having a second axis of symmetry, said first and second axes being generally collinear;
wherein said shunt coil comprises a shunt axis of symmetry disposed generally perpendicular to said first axis of symmetry.
10. The controllable transformer of claim 9 wherein:
said main magnetic core comprises a first side and a second side, said first side being parallel to said second side;
said shunt magnetic core is disposed proximate said first side and said second side; and said shunt coil is about equidistant said primary and secondary coils.
said main magnetic core comprises a first side and a second side, said first side being parallel to said second side;
said shunt magnetic core is disposed proximate said first side and said second side; and said shunt coil is about equidistant said primary and secondary coils.
11. A controllable transformer comprising:
a secondary magnetic path;
a shunt magnetic path in parallel with said secondary magnetic path;
a shunt coil inductively coupled to said shunt magnetic path; and a switch coupled to said shunt coil, wherein power for control of said switch is derived from said shunt coil.
a secondary magnetic path;
a shunt magnetic path in parallel with said secondary magnetic path;
a shunt coil inductively coupled to said shunt magnetic path; and a switch coupled to said shunt coil, wherein power for control of said switch is derived from said shunt coil.
12. The controllable transformer of claim 11 wherein said shunt magnetic path includes an air gap.
13. The controllable transformer of claim 11 further comprising:
a primary coil inductively coupled to a primary magnetic path, said primary coil having a first axis of symmetry; and a secondary coil inductively coupled to a secondary magnetic path, said secondary coil having a second axis of symmetry, said first axis of symmetry being collinear with said second axis of symmetry;
wherein said shunt coil comprises a shunt axis of symmetry disposed generally perpendicular to said first axis of symmetry.
a primary coil inductively coupled to a primary magnetic path, said primary coil having a first axis of symmetry; and a secondary coil inductively coupled to a secondary magnetic path, said secondary coil having a second axis of symmetry, said first axis of symmetry being collinear with said second axis of symmetry;
wherein said shunt coil comprises a shunt axis of symmetry disposed generally perpendicular to said first axis of symmetry.
14. The controllable transformer of claim 13 wherein the reluctance of said secondary magnetic path is less than the reluctance of said shunt magnetic path.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/661,471 | 1991-02-26 | ||
| US07/661,471 US5187428A (en) | 1991-02-26 | 1991-02-26 | Shunt coil controlled transformer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2080461A1 true CA2080461A1 (en) | 1992-08-27 |
Family
ID=24653743
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002080461A Abandoned CA2080461A1 (en) | 1991-02-26 | 1992-02-24 | Shunt coil controlled transformer |
Country Status (4)
| Country | Link |
|---|---|
| US (2) | US5187428A (en) |
| EP (1) | EP0530347A4 (en) |
| CA (1) | CA2080461A1 (en) |
| WO (1) | WO1992015051A1 (en) |
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| US5672963A (en) * | 1991-02-26 | 1997-09-30 | Illinois Tool Works Inc. | Variable induction control led transformer |
| JPH065448A (en) * | 1992-06-22 | 1994-01-14 | Matsushita Electric Ind Co Ltd | Choke coil and power source |
| CA2139715A1 (en) * | 1994-02-10 | 1995-08-11 | Richard M. Hutchison | Synchronized pulse arc starter and stabilizer for arc welding |
| US5523673A (en) * | 1994-03-04 | 1996-06-04 | Marelco Power Systems, Inc. | Electrically controllable inductor |
| US5513093A (en) * | 1994-03-11 | 1996-04-30 | Miller Electric Mfg. Co. | Reduced open circuit voltage power supply and method of producing therefor |
| US5731666A (en) * | 1996-03-08 | 1998-03-24 | Magnetek Inc. | Integrated-magnetic filter having a lossy shunt |
| SE510192C2 (en) | 1996-05-29 | 1999-04-26 | Asea Brown Boveri | Procedure and switching arrangements to reduce problems with three-tier currents that may occur in alternator and motor operation of AC machines connected to three-phase distribution or transmission networks |
| DE69727917T2 (en) | 1996-05-29 | 2005-01-27 | Abb Ab | ELECTROMAGNETIC DEVICE |
| EP1016185A1 (en) | 1996-05-29 | 2000-07-05 | Abb Ab | Insulated conductor for high-voltage windings and a method of manufacturing the same |
| ES2208904T3 (en) | 1996-05-29 | 2004-06-16 | Abb Ab | CONDUCTOR FOR HIGH VOLTAGE WINDING AND A ROTARY ELECTRIC MACHINE THAT INCLUDES A WINDING THAT INCLUDES THE DRIVER. |
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| SE512917C2 (en) | 1996-11-04 | 2000-06-05 | Abb Ab | Method, apparatus and cable guide for winding an electric machine |
| SE515843C2 (en) | 1996-11-04 | 2001-10-15 | Abb Ab | Axial cooling of rotor |
| SE510422C2 (en) | 1996-11-04 | 1999-05-25 | Asea Brown Boveri | Magnetic sheet metal core for electric machines |
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| SE9704421D0 (en) | 1997-02-03 | 1997-11-28 | Asea Brown Boveri | Series compensation of electric alternator |
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| HUP0101186A3 (en) | 1997-11-28 | 2002-03-28 | Abb Ab | Method and device for controlling the magnetic flux with an auxiliary winding in a rotaing high voltage electric alternating current machine |
| US6801421B1 (en) * | 1998-09-29 | 2004-10-05 | Abb Ab | Switchable flux control for high power static electromagnetic devices |
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| US7023313B2 (en) * | 2003-07-16 | 2006-04-04 | Marvell World Trade Ltd. | Power inductor with reduced DC current saturation |
| US7307502B2 (en) * | 2003-07-16 | 2007-12-11 | Marvell World Trade Ltd. | Power inductor with reduced DC current saturation |
| US7872454B2 (en) * | 2003-08-21 | 2011-01-18 | Marvell World Trade Ltd. | Digital low dropout regulator |
| US7760525B2 (en) * | 2003-08-21 | 2010-07-20 | Marvell World Trade Ltd. | Voltage regulator |
| US8324872B2 (en) | 2004-03-26 | 2012-12-04 | Marvell World Trade, Ltd. | Voltage regulator with coupled inductors having high coefficient of coupling |
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| US20100019875A1 (en) * | 2008-07-25 | 2010-01-28 | Ampower Technology Co., Ltd. | High voltage transformer employed in an inverter |
| NO330773B1 (en) * | 2009-12-18 | 2011-07-11 | Vetco Gray Scandinavia As | Transformer |
| CN201859742U (en) * | 2010-10-15 | 2011-06-08 | 国琏电子（上海）有限公司 | High-voltage transformer |
| CA3027172C (en) | 2016-06-30 | 2022-09-06 | Timpson Electrical & Aerial Services, LLC | High voltage training device and system and method thereof |
| CN111085767A (en) * | 2019-12-30 | 2020-05-01 | 桂林理工大学 | Electron beam cathode heating voltage stabilizer |
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| US4876638A (en) * | 1988-02-10 | 1989-10-24 | Electronic Research Group, Inc. | Low-noise switching power supply having variable reluctance transformer |
-
1991
- 1991-02-26 US US07/661,471 patent/US5187428A/en not_active Expired - Fee Related
-
1992
- 1992-02-24 WO PCT/US1992/001464 patent/WO1992015051A1/en not_active Application Discontinuation
- 1992-02-24 EP EP19920907457 patent/EP0530347A4/en not_active Withdrawn
- 1992-02-24 CA CA002080461A patent/CA2080461A1/en not_active Abandoned
- 1992-09-30 US US07/954,300 patent/US5363035A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0530347A1 (en) | 1993-03-10 |
| WO1992015051A1 (en) | 1992-09-03 |
| US5187428A (en) | 1993-02-16 |
| US5363035A (en) | 1994-11-08 |
| EP0530347A4 (en) | 1993-12-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |