Patent US4208709A successfully refreshed from Google Patents.
US4208709A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rectifiers
Assignee: EMI Group Electronics Ltd
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Filing: 1978-07-03
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Granted: 1980-06-17
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Expires: 1998-07-03
Abstract
Abstract A rectifier unit for 3-phase a.c. to d.c. conversion is of the type having a transformer with a star-connected and a delta-connected secondary the outputs of which are rectified and combined to give 12-pulse operation. To reduce the danger of current imbalance between the two secondaries, a compensating transformer unit is interposed between the secondaries and the rectifiers which modifies the signals such that any difference in the current drawn from one secondary compared with the other tends to equalize the current drawn from the secondaries. The compensating transformer unit can take the form of 3 individual transformer units but is preferably a single transformer with 3 limbs, each of which carries a main winding connected to one secondary and two opposed subsidiary windings which receive the phases from the other secondary which are closest to and on either side of the phase of the associated main winding.
Inventors
- 👤 Martin H. F. Garnham
- 👤 Frank T. Bennell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:44
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/02; H02M7/04; H02M7/06; H02M7/08
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
165 words
A rectifier unit for producing unidirectional current from an n-phase a.c. supply, where n is equal to 3 or an integer greater than 3, the unit comprising: means for providing from the supply two n-phase sources which differ in phase by 1/4n cycles, or an odd integral multiple thereof; two n-phase bridge rectifiers having their inputs connected to receive the signals from the two sources and their outputs coupled together to provide the output of the unit; and compensating means coupled between the sources and the rectifiers for modifying the signals applied to the latter, the compensating means comprising n transformer sections each coupled to at least one output of one of the sources and at least two outputs of the other source, and being arranged such that any difference in the current drawn from one source, compared with the current with the same phase drawn from the other source, produces a compensating magnetic flux tending to equalize the current drawn from the two sources.
Claim 2
Dependent Claim
165 words
A rectifier unit for producing unidirectional current from an n-phase a.c. supply, where n is equal to 3 or an integer greater than 3, the unit comprising: means for providing from the supply two n-phase sources which differ in phase by 1/4n cycles, or an odd integral multiple thereof; two n-phase bridge rectifiers having their inputs connected to receive the signals from the two sources and their outputs coupled together to provide the output of the unit; and compensating means coupled between the sources and the rectifiers for modifying the signals applied to the latter, the compensating means comprising n transformer sections each coupled to at least one output of one of the sources and at least two outputs of the other source, and being arranged such that any difference in the current drawn from one source, compared with the current with the same phase drawn from the other source, produces a compensating magnetic flux tending to equalize the current drawn from the two sources.
Claim 3
Dependent Claim
24 words
A rectifier unit according to claim 1, wherein the means for providing two n-phase sources comprises a transformer with two differently connected secondary windings.
Claim 4
Dependent Claim
11 words
A rectifier unit according to claim 2, wherein n equals three.
Claim 5
Dependent Claim
22 words
A rectifier unit according to claim 3, wherein one secondary winding is in star configuration and the other is in delta configuration.
Claim 6
Dependent Claim
20 words
A rectifier unit according to claim 1, wherein the n transformer sections are respectively constituted by n individual transformer units.
Claim 7
Dependent Claim
23 words
A rectifier unit according to claim 1, wherein the n transformer sections are respectively constituted by n limbs of a single transformer unit.
Claim 8
Dependent Claim
24 words
A rectifier unit according to claim 1, wherein each transformer section comprises three or more windings each connected to said outputs of said sources.
Claim 9
Dependent Claim
59 words
A rectifier unit according to claim 7, wherein each of the transformer sections comprises a main winding coupled to a respective phase of one of the sources and two subsidiary windings which is coupled to the other source to receive those phases therefrom which are closest to and on either side of the phase of the associated main winding.
Claim 10
Dependent Claim
35 words
A rectifier unit according to claim 8, wherein the two subsidiary windings of each section are opposed to each other and each subsidiary winding has 1 /√3 times as many turns as the main winding.
Claim 11
Dependent Claim
37 words
A rectifier unit according to claim 1, wherein any current difference causes a resultant magnetic flux in one or more of the transformer sections which tends to equalize the currents without additional current monitoring and control circuits.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-06-17 | 1983-12-17 | 1984-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-06-17 | 1987-12-17 | 1988-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-06-17 | 1991-12-17 | 1992-06-17 | $7700.00 | Window Closed / Lapsed |