Critical Bus Voltage Distortion in High Power UPS Systems

I.F. Bitterlin (UK)


Voltage Distortion, Rotary UPS, Static UPS, Emergency Generation, Computer Centre


Most IT hardware users assume that installing an Uninterruptible Power Supply (UPS) system will solve all their power problems and deliver to their critical load a high fidelity sine-wave voltage waveform. However much IT hardware draws non-linear current and is predominately single phase – producing high Triplen harmonics and associated neutral currents. Different types of UPS system and their bypass arrangements do not respond to such current demands in the same way. Users often also ignore many of the practical consequences of power equipment maintenance and even failure. This paper intends to review the basis of current distortion and the fundamental effects it can have on the voltage fidelity of various types of UPS and their associated back up power systems.

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