One of the major applications of online static UPS systems is to feed computer systems. The computer as a load for the UPS system is a nonlinear load, which consumes current with high crest factor CF (CF=I/sub Peak//l/sub rms/) when the UPS output voltage is pure sine wave, and this overloads the UPS components. In this paper, simulation is applied to investigate the effect of different UPS output waveforms on the crest factor and efficiency. The efficiency is an important factor which may conflict with the crest factor, since a flat-top waveform may improve the crest factor while its harmonics cause more losses that decrease the system efficiency. A UPS configuration is then proposed that generates an output waveform with moderate crest factor and efficiency, and is thus more suitable for computer systems.
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