The invention relates to power distribution apparatus and methods and, more particularly, to transformer apparatus and methods.
There is an ongoing quest for increased energy efficiencies in data centers and similar facilities. One technique for increasing efficiency is to increase the voltage used for power distribution in a facility. For example, current computer power supplies commonly can operate from 230V without modification. Replacing a 120/208V wye distribution system in a data center with a 230/400V wye system could allow elimination of isolation transformers used to step down to 120/208V, thus eliminating the approximate 2% loss associated with the isolation transformers.
In the U.S., however, facility power distribution systems commonly are 480V delta and, in rarer cases, 277/480V wye. Computer power supplies commonly cannot operate at 480V or 277V. Thus, provision of power to such devices may require either modification of the power supplies or conversion of the AC input to 230/400V wye.
A common approach illustrated in
Another technique, illustrated in
Some embodiments of the present invention provide a transformer including first, second and third magnetic cores, a first winding on the first magnetic core and having a first terminal configured to be connected to a first AC input phase, a second winding on the second magnetic core and having a first terminal configured to be connected to a second AC input phase, a third winding on the third magnetic core and having a first terminal configured to be connected to a third AC input phase, a fourth winding on the first magnetic core and having a first terminal connected to a second terminal of the third winding and a second terminal configured to be connected to an AC neutral, a fifth winding on the second magnetic core and having a first terminal connected to a second terminal of the first winding and a second terminal configured to be connected to the AC neutral and a sixth winding on the third magnetic core and having a first terminal connected to a second terminal of the second winding and a second terminal configured to be connected to the AC neutral. The transformer further includes a seventh winding on the first magnetic core and having a first terminal connected to the first terminal of the first winding, an eighth winding on the second magnetic core and having a first terminal connected to the first terminal of the second winding, a ninth winding on the third magnetic core and having a first terminal connected to the first terminal of the third winding, a tenth winding on the first magnetic core and having a first terminal connected to a second terminal of the ninth winding and a second terminal configured to provide a first AC output phase, an eleventh winding on the second magnetic core and having a first terminal connected to a second terminal of the seventh winding and a second terminal configured to provide a second AC output phase and a twelfth winding on the third magnetic core and having a first terminal connected to a second terminal of the eight winding and a second terminal configured to provide a third AC output phase. The first, second and third magnetic cores may include first, second and third cores of a three-phase magnetic core structure or the first, second and third magnetic cores may include respective discrete single-phase magnetic cores. The seventh, eighth, ninth, tenth, eleventh and twelfth windings may provide a voltage transformation between the first, second and third AC input phases and the first, second and third AC output phases of approximately 277V phase-to-neutral to 230V phase-to-neutral.
In further embodiments, a transformer includes a zigzag transformer comprising first, second and third magnetic cores. The transformer further includes an auxiliary winding set comprising respective pairs of series-connected windings on respective pairs of the first, second and third magnetic cores, the pairs of series-connected windings having respective first terminals connected to respective AC phases of the zigzag autotransformer and respective second terminals configured to provide respective AC output phases. The first, second and third magnetic cores may include first, second and third cores of a three-phase magnetic core structure or the first, second and third magnetic cores may include discrete single-phase magnetic cores. The auxiliary winding set may be configured to provide a voltage transformation between the first, second and third AC phases of the zigzag transformer and the first, second and third AC output phases of approximately 277V phase-to-neutral to 230V phase-to-neutral.
Additional embodiments of the present invention provide methods of operating a zigzag transformer comprising first, second and third magnetic cores. An auxiliary winding set is provided, the auxiliary winding set including respective pairs of series-connected windings on respective pairs of the first, second and third magnetic cores, the pairs of series-connected windings having respective first terminals connected to respective AC phases of the zigzag transformer. Respective phases of an AC source are connected to respective ones of the AC phases of the zigzag transformer to provide respective AC output phases at respective second terminals of the pairs of series-connected windings. An unbalanced load is connected to the second terminals of the pairs of series-connected windings.
Specific exemplary embodiments of the invention now will be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Additional series-connected pairs of windings are connected to AC input phase terminals H1, H2, H3 and provide a voltage transformation between the voltages at the terminals H1, H2, H3 and voltages at AC output phase terminals H1′, H2′, H3′. In particular, seventh, eight and ninth windings 116a, 116b, 116c are provided on respective ones of the first, second and third cores 120a, 120b, 120c, and are connected to respective ones of the first, second and third windings 112a, 112b, 112c. A tenth winding 118a is on the first core 120a and is connected in series with the ninth winding 116c. An eleventh winding 118b is on the second core 120b and is connected in series with the seventh winding 116a. A twelfth winding 118c is on the third core 120c and is connected in series with the eighth winding 116b. According to some embodiments of the present invention, the seventh, eighth, ninth, tenth, eleventh and twelfth windings 116a, 116b, 116c, 118a, 118b, 118c support a translation from a V phase to neutral voltage at the terminals H1, H2, H3 to a V phase to neutral voltage at the phase terminals H1′, H2′, H3′.
The transformer 400 may be described as a zigzag transformer, including the first, second, third, fourth, fifth an sixth windings 112a, 112b, 112c, 114a, 114b, 114c, which provides a neutral, and an auxiliary winding set, including the seventh, eighth, ninth, tenth, eleventh and twelfth windings 116a, 116b, 116c, 118a, 118b, 118c, which provides a voltage transformation. The transformer 400 can be constructed using three individual cores for the cores 120a, 120b, 120c, or further reduction of the magnetic structure may be achieved by combining the three cores 120a, 120b, 120c in a single, three-phase core structure.
Embodiments of the present invention may provide several advantages. Simply tapping a winding of a zigzag transformer (e.g., the transformer of
In the drawings and specification, there have been disclosed exemplary embodiments of the invention. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined by the following claims.
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Number | Date | Country | |
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20100148898 A1 | Jun 2010 | US |