Cyberpower Surge Protector - For Uninterruptible Power Supply

Thirds are most likely the most challenging harmonic when it comes to neutral conductor loading inside a three-phase system. Whereas other harmonics cancel each other out, third-harmonics are in phase with one another and exhibit a summing impact which greatly increases the present - potentially overloading conductors and switchgear.

Harmonics and total energy factor - implications for UPS sizing. Harmonics are also closely related to power factor management - and another key aspect of uninterruptible power supply program style and implementation. The displacement energy factor is only applicable to the fundamental frequency (50Hz in Europe) and therefore doesn't take into account the power factor generated by any harmonics induced into the mains energy supply by the load itself (referred to as the distortion power factor and produced by the harmonics produced by non-linear loads). The mixture with the displacement power factor and the distortion power factor gives what's recognized to UPS systems specialists as the accurate energy factor. When properly sizing a UPS, an understanding of this is critical.

Mitigation of total harmonics distortion. Harmonics problems need to be addressed in the design stage of any energy continuity strategy. Not least, simply because customers are responsible for the harmonic levels introduced into their three-phase mains power supply.

A UPS can occasionally be fitted with a harmonic filter (post installation) but this may be a pricey and inelegant answer as extensive internal wiring changes might be needed. For a transformer-based UPS, utilizing a 12-pulse rectifier in place of a 6-pulse set will decrease the levels of THDi (total harmonic distortion). Coupling this having a passive filter will offer further reduction to around 4%.

For a transformerless uninterruptible energy supply, THDi levels of less than 4% can be achieved by installing an active harmonic filter. Nevertheless, levels as low as 3% can now be achieved by some designs whose rectifiers are IGBT (Insulated Gate Bipolar Transistor) based. This can eliminate the need for an extra active harmonic filter and simplify the UPS design procedure. Such styles are expected to turn out to be the norm: not only do they decrease initial costs, but they permit a smaller UPS system footprint whilst increasing input power elements.

Active harmonic filters decrease the impact of leading energy factors. When designing a power continuity strategy and UPS program, numerous methods can be applied to decrease the impact of leading power elements (where the current waveform leads the voltage waveform): ensuring that leading power elements represent a smaller percentage of the UPS load, installing power factor correction between the UPS and the load, increasing UPS size (and that of any standby generation capacity) and specifying a UPS with leading energy factor capabilities.

A popular approach to decrease the impact of leading energy factors on a UPS installation is to use an active harmonic filter with power factor correction on the UPS output. This presents the UPS with a much more acceptable load, but outcomes in greater capital and installation expenses, lower efficiency and a greater footprint.