Electric power conversion systems – Cascaded or combined – diverse conversions in which the... – Current and phase
Patent
1991-06-28
1992-04-21
Wong, Peter S.
Electric power conversion systems
Cascaded or combined, diverse conversions in which the...
Current and phase
363154, 363155, 323361, 323215, H02M 502
Patent
active
051074109
ABSTRACT:
A method and apparatus for providing a source of alternating current electrical power to a plurality of loads in an office environment, including a plurality of non-linear loads which draw power for only a portion of the alternating current cycle, includes an input source of three-phase electrical power to a primary side of a power transforming device which provides an output at its secondary side which comprises at least six phases and a shared neutral. The plurality of loads are evenly distributed between each phase of the output power source and the shared neutral so as to reduce by current cancellation the current which would otherwise flow in the shared neutral conductor due to the presence of the non-linear loads. Each of the six phases is separated from the other by 120 electrical degrees, and the fourth, fifth and sixth phases are separated from the first, second and third phases, respectively, by 180 electrical degrees. In a preferred embodiment, two sets of six phases are provided, with each of the phases in the first set shifted, relative to respective phases of the second set, so as to reduce variations in the level of instantaneous power drawn from the input source which would otherwise occur due to the presence of the non-linear loads. Benefits of the invention include lower ground to neutral noise, reduced transmission losses, more accurate power measurement by induction watt-hour meters, and fewer instances of neutral current overload.
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"Nonlinear Loads Mean Trouble", Arthur Freund, Senior Editor, Electrical Construction & Maintenance, Mar. 1988.
"Double the Neutral and Derate the Transformer--or Else!", Arthur Freund, Senior Editor, Electrical Construction & Maintenance, Dec. 1988.
"Harmonic Analyzer Helps Solve Power Problems", David Kreiss, Electrical Construction & Maintenance, Mar. 1989.
Marsh John K.
Zemen, Jr. Russell E.
Group Dekko International
Wong Peter S.
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