A 1,000 kVA transformer feeding six-pulse VFDs, spot welders and single-phase loads is a textbook harmonic source. Field measurements on such busbars typically show current THD of 25–40 % at the PCC, with the 5th and 7th orders dominant. Third-order currents add up in the neutral conductor and overheat it. Fixed capacitor banks rarely survive this environment. When the natural resonan...
Harmonics are extra currents and voltages at integer multiples of the supply frequency that non-linear loads draw on top of the fundamental sine wave. Their effect is costly: transformers, motors and neutral conductors overheat, relays mis-trip, and equipment life shortens even below rated load. This guide covers measurement at the point of common coupling (PCC) and how to compare the main mitigat...
An Active Harmonic Filter (AHF) is a parallel-connected, closed-loop power-electronic device that measures load harmonic current with current transformers and injects an opposing current to cancel distortion at the point of common coupling (PCC). The engineering conclusion is blunt: an AHF is selected against the measured harmonic spectrum, load variability, site ambient temperature, and network i...
YT Electric (Shanghai Yingtong Electric Co., Ltd) is a Shanghai-headquartered manufacturer of power quality equipment — active harmonic filters (AHF), static var generators (SVG and ASVG), hybrid reactive power compensation, medium-voltage STATCOMs and energy storage systems — serving industrial plants, data centres, commercial buildings, hospitals, rail and renewable-energy projects. ...
Most AHF and SVG quotations are built backwards. A buyer collects a short-circuit level, a transformer rating and a target THDi, then asks three suppliers for a price. The result is a device sized to a guess rather than to the disturbance. A power quality report already contains most of what is needed to size a harmonic filter or reactive compensator correctly, provided the reader knows which colu...
Industrial efficiency losses are not always mechanical. A plant can keep every machine healthy and still lose energy, capacity and uptime to harmonics, reactive power and three-phase current imbalance that never appear on a maintenance checklist. VFDs, rectifier-fed equipment and fast-switching electronics make production more efficient while making the network underneath less forgiving. This arti...
Capacitor bank overheating after adding VFDs is a power quality symptom, not a capacitor defect. VFD rectifiers inject harmonic current, the bank offers a low-impedance path at those frequencies, and parallel resonance between the bank and the supply can amplify that current until fuses open, contactors chatter and capacitor cans swell. A capacitor bank supplies reactive power to correct power fac...
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