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US 5,638,266 AGranted
Free wheel diode arrangement for neutral point clamped electric power conversion apparatus
AssigneesHitachi, Ltd., Hitachi Mito Engineering Co., Ltd.
InventorsAkira Horie, Syuuji Saitou, Hiroshi Itahana
Life of this patent
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Abstract
The invention is directed to a neutral point clamped electric power conversion apparatus having four semiconductor switching elements connected in series. The capacity of outer free wheel diodes connected in reverse parallel with outer semiconductor switching elements are increased compared to that of inner free wheel diodes, thereby minimizing, an imbalance in losses between the inner and the outer free wheel diodes.
Claims5
An electrical power conversion apparatus comprising:
- a first series circuit including first, second, third and fourth switching elements connected in series;
- a second series circuit of clamping diodes connected in reverse parallel with said first series circuit, one end thereof being connected to a first connection node disposed between said first and second switching elements and another end thereof being connected to a second connection node disposed between said third and fourth switching elements, and a plurality of free wheel diodes, one of said free wheel diodes being connected in reverse parallel with each of said switching elements;
- wherein
- free wheel diodes connected in reverse parallel to said first switching element and said fourth switching element respectively each have a current capacity which is greater than a current capacity of free wheel diodes connected in reverse parallel to said second switching element and said third switching element, whereby an imbalance in power loss between said diodes connected in parallel with said first and fourth switching elements and said diodes connected in parallel with said second and third switching elements, is substantially diminished.
1 more element
Dependencies are inferred from the claim text.