EP0302856B1 - Improvements in ferroresonant constant-voltage transformers - Google Patents
Improvements in ferroresonant constant-voltage transformers Download PDFInfo
- Publication number
- EP0302856B1 EP0302856B1 EP87901457A EP87901457A EP0302856B1 EP 0302856 B1 EP0302856 B1 EP 0302856B1 EP 87901457 A EP87901457 A EP 87901457A EP 87901457 A EP87901457 A EP 87901457A EP 0302856 B1 EP0302856 B1 EP 0302856B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- core
- cores
- wound
- gap
- magnetic circuit
- 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 - Lifetime
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/04—Regulating voltage or current wherein the variable is ac
- G05F3/06—Regulating voltage or current wherein the variable is ac using combinations of saturated and unsaturated inductive devices, e.g. combined with resonant circuit
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F30/00—Fixed transformers not covered by group H01F19/00
- H01F30/06—Fixed transformers not covered by group H01F19/00 characterised by the structure
- H01F30/10—Single-phase transformers
Definitions
- the present invention relates to ferroresonant constant-voltage transformers. These are now widely used in order to obtain a stabilized voltage. These transformers are enjoying an increased sale on the market owing to the fact that many electronic products now in common use need a constant imput voltage in order to work properly.
- GB-A-1-020.093 foresees a transformer having two cores: one with and the other without gap, both being provided with two adjacent portions on which the secondary winding is wound while the primary winding is wound only on the core's portion without gap, thus with a saturated magnetic circuit.
- This arrangement is quite inefficient because an input voltage increment causes the current to rise while the magnetic permeability of the material is reduced tending to saturation. At this point the primary winding subjected to a very high current, produces an anomalous heating and thus excessive heat losses.
- FR-A-2.140.038 shows two continuous cores (without gap) also having two adjacent portions on which a primary winding is wound.
- a feed back secondary winding is also necessary for obtaining a constant voltage besides the main secondary winding. This complicates the construction and makes it more expensive and less reliable.
- Aim of this invention is to carry out an improved ferroresonant transformer having a good efficiency, better than that of the present transformers, thus enabling considerable variations comprised between -50% and +30% obtaining output variations comprised within ⁇ 2%.
- the proposed transformer is made up of two cores 10 and 20 each one comprising a single spiral wound core sheet strip that is cut in half to form two C-shaped portions respectively 15 and 16; 25 and 26. Both cores have a portion, respectively 11 and 21, that is adjacent to the other portion 11 or 21. Around both adjacent portions the transformer's primary P is wound. Around another section 22 of the saturated magnetic core 20 (without gap) the secondary S is wound.
- Core 10 is made so as to work always in a linear magnetic field, whilst core 20 is made so as to work always with a saturated magnetic field. To do so, the facing surfaces of portions 25 and 26 of core 20 are lapped in a mirror-like way on their lacing surfaces 27, then they are drawn together so that in between portions 25 and 26 the gap is practically "zero".
- Core 10, on which only the primary winding P is wound is instead provided with two gaps 18 between the two lacingsurfaces 17.
- the total value of the two gaps is preferably comprised between 000,2 and 2 per thousand of the core's magnetic circuit, i.e. for a 20 W power the circuit is about 130 mm. and the two gaps' total value is 0,05 mm. equal to the 0,4 per thousand, for a 250 W power the magnetic circuit is about 260 mm. and the total value of the two gaps is 0,4 mm. equal to the 1,5 per thousand.
- the extension of the magnetic field of core 10 is solely that strictly necessary for accomodating winding P.
- the extension of core 20's magnetic circuit is on the contrary much greater particularly it is at least a 10% bigger than the magnetic field extension of core 10.
- the two cores are preferably obtained by winding a magnetic core shaped as a continuous strip whose grains, as known, are positioned in the direction of lamination. This continuous strip is spiral wound starting from the inner winding's surface indicated with 13 and respectively with 23, and continuing until the outside surface, indicated respectively with 14 and 24 is reached. Each annular core is then cut in half thus forming two portions having opposed facing surfaces 17 and 27.
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)
- Coils Of Transformers For General Uses (AREA)
- Coils Or Transformers For Communication (AREA)
Abstract
Description
- The present invention relates to ferroresonant constant-voltage transformers. These are now widely used in order to obtain a stabilized voltage. These transformers are enjoying an increased sale on the market owing to the fact that many electronic products now in common use need a constant imput voltage in order to work properly.
- Many transformers of this kind are already known However, they are relatively inefficient and thus they easily heat up if the voltage increase is very high.
- It is moreover known that the magnetic permeability of a core sheet is greater in the direction of the lamination. On the contrary, magnetic losses are smaller in this direction. The known ferroresonant transformers use blank superimposed core sheets having anisotropy in a single direction, in the direction of E's legs, whilst the other sides do not enjoy this privilege and thus suffer high magnetic losses.
- GB-A-1-020.093 foresees a transformer having two cores: one with and the other without gap, both being provided with two adjacent portions on which the secondary winding is wound while the primary winding is wound only on the core's portion without gap, thus with a saturated magnetic circuit. This arrangement is quite inefficient because an input voltage increment causes the current to rise while the magnetic permeability of the material is reduced tending to saturation. At this point the primary winding subjected to a very high current, produces an anomalous heating and thus excessive heat losses.
- FR-A-2.140.038 shows two continuous cores (without gap) also having two adjacent portions on which a primary winding is wound. However for obtaining a constant voltage besides the main secondary winding a feed back secondary winding is also necessary. This complicates the construction and makes it more expensive and less reliable.
- Aim of this invention is to carry out an improved ferroresonant transformer having a good efficiency, better than that of the present transformers, thus enabling considerable variations comprised between -50% and +30% obtaining output variations comprised within ±2%.
- Straiting from the features of the preamble of claim 1 (known from 215-A-3 708 744) the aim of the invention is attained by combining those known features with the characterising features of claim 1.
- The invention will now be better clarified by an exemplary embodiment that has been illustrated in the enclosed drawings, in which:
- Fig. 1 is a frontal view of the proposed transformer; and
- Fig. 2 is a side view of the same transformer.
- Reference being made to the drawings it will be noted that the proposed transformer is made up of two
cores other portion 11 or 21. Around both adjacent portions the transformer's primary P is wound. Aroundanother section 22 of the saturated magnetic core 20 (without gap) the secondary S is wound. -
Core 10 is made so as to work always in a linear magnetic field, whilstcore 20 is made so as to work always with a saturated magnetic field. To do so, the facing surfaces ofportions core 20 are lapped in a mirror-like way on theirlacing surfaces 27, then they are drawn together so that in betweenportions Core 10, on which only the primary winding P is wound is instead provided with twogaps 18 between the twolacingsurfaces 17. The total value of the two gaps is preferably comprised between 000,2 and 2 per thousand of the core's magnetic circuit, i.e. for a 20 W power the circuit is about 130 mm. and the two gaps' total value is 0,05 mm. equal to the 0,4 per thousand, for a 250 W power the magnetic circuit is about 260 mm. and the total value of the two gaps is 0,4 mm. equal to the 1,5 per thousand. - As will be noticed from the drawings the extension of the magnetic field of
core 10 is solely that strictly necessary for accomodating winding P. The extension ofcore 20's magnetic circuit is on the contrary much greater particularly it is at least a 10% bigger than the magnetic field extension ofcore 10. - The two cores are preferably obtained by winding a magnetic core shaped as a continuous strip whose grains, as known, are positioned in the direction of lamination. This continuous strip is spiral wound starting from the inner winding's surface indicated with 13 and respectively with 23, and continuing until the outside surface, indicated respectively with 14 and 24 is reached. Each annular core is then cut in half thus forming two portions having opposed facing
surfaces - With the proposed winding there is therefore a greater efficiency because the anisotropy created by the sheet is profitably exploited. On operation, when the input voltage increases, the permeability of
core 10 linear magnetic circuit remains practically constant. Therefore in the primary winding the current will increase in a linear way when the input voltage increases. Therefore a phenomenon of anomalous heating will not occur.
Claims (2)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT87901457T ATE63648T1 (en) | 1986-02-28 | 1987-02-24 | CONSTANT VOLTAGE FERRORESONANT TRANSFORMERS. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT1960086 | 1986-02-28 | ||
IT19600/86A IT1190079B (en) | 1986-02-28 | 1986-02-28 | IMPROVEMENTS TO IRON-RESONANCE TRANSFORMERS (FERRORESONANT CONSTANT-VOLTAGE TRANSFORMER) |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0302856A1 EP0302856A1 (en) | 1989-02-15 |
EP0302856B1 true EP0302856B1 (en) | 1991-05-15 |
Family
ID=11159362
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP87901457A Expired - Lifetime EP0302856B1 (en) | 1986-02-28 | 1987-02-24 | Improvements in ferroresonant constant-voltage transformers |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0302856B1 (en) |
AU (1) | AU7125387A (en) |
IT (1) | IT1190079B (en) |
WO (1) | WO1987005412A1 (en) |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE1149809B (en) * | 1961-05-12 | 1963-06-06 | Frako Kondensatoren Und Appbau | Stabilized power rectifier circuit |
GB1050605A (en) * | 1961-09-21 | |||
DE2225720A1 (en) * | 1971-05-28 | 1972-12-14 | Parlour William J Ltd | Electric device |
US3708744A (en) * | 1971-08-18 | 1973-01-02 | Westinghouse Electric Corp | Regulating and filtering transformer |
-
1986
- 1986-02-28 IT IT19600/86A patent/IT1190079B/en active
-
1987
- 1987-02-24 WO PCT/EP1987/000101 patent/WO1987005412A1/en active IP Right Grant
- 1987-02-24 EP EP87901457A patent/EP0302856B1/en not_active Expired - Lifetime
- 1987-02-24 AU AU71253/87A patent/AU7125387A/en not_active Abandoned
Also Published As
Publication number | Publication date |
---|---|
IT8619600A0 (en) | 1986-02-28 |
AU7125387A (en) | 1987-09-28 |
WO1987005412A1 (en) | 1987-09-11 |
IT1190079B (en) | 1988-02-10 |
IT8619600A1 (en) | 1987-08-28 |
EP0302856A1 (en) | 1989-02-15 |
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