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1. (WO2017020644) METHOD AND APPARATUS FOR REDUCING EXCITATION CURRENT OF TRANSFORMER DURING BYPASS CONDUCTED BY ISOLATED UPS

Pub. No.:    WO/2017/020644    International Application No.:    PCT/CN2016/083986
Publication Date: Fri Feb 10 00:59:59 CET 2017 International Filing Date: Wed Jun 01 01:59:59 CEST 2016
IPC: H02P 13/00
Applicants: ZHANG ZHOU KE HUA TECHNOLOGY CO., LTD.
漳州科华技术有限责任公司
Inventors: CAO, Zhenhua
曹振华
HUANG, Zhenmin
黄振民
CHEN, Jun
陈君
Title: METHOD AND APPARATUS FOR REDUCING EXCITATION CURRENT OF TRANSFORMER DURING BYPASS CONDUCTED BY ISOLATED UPS
Abstract:
A method and apparatus for reducing an excitation current of a transformer during bypass conducted by an isolated UPS. The method comprises: step S1: obtaining, in real time, a zero crossing point of a UPS-input alternating current, and obtaining frequency f of the UPS-input alternating current according to the time difference between two adjacent zero crossing points; step S2: determining whether the frequency of the UPS-input alternating current satisfies fmin≤f≤fmax, and if satisfied, proceeding to step S3, otherwise, returning to step S1; step S3: selecting the initial value of a as 1, wherein a is a positive integer; step S4: UPS controlling a bypass controllable silicon SCR to be in a conductive state from a tip time point to a next adjacent zero crossing point ti1 during the current ith half sine wave period of the UPS-input alternating current, wherein tip=ti0+(N-a)/2Nf, N is a positive integer, ti0 is the first zero crossing point time point of the current ith half sine wave period, where 1≤i≤N, and i is a positive integer; and step S5: progressively increasing the value of a, and determining whether a is less than or equal to N-1, and if yes, returning to step S4, otherwise, ending the process. The method and apparatus guarantee that the output excitation current of the isolated transformer is minimal, without damaging the bypass controllable silicon SCR. AA%%%SCR Driving