A facility can operate normally on utility power and develop power quality problems after transferring to a standby generator. Drives trip, UPS systems report input faults and lights flicker—even though the load has not changed. Nonlinear loads are usually already generating harmonic current. The generator provides a weaker source, allowing the same current distortion to create greater volta...
Transformer Overheating Explained: Why It Happens Below Rated Load A transformer can run unusually hot even when the connected load appears safely below its nameplate rating. Current may seem acceptable while winding or enclosure temperatures continue rising. This often happens because loading is assessed only in kilowatts or average amperes. Harmonics, imbalance, poor power factor and inad...
Even-order harmonics are current and voltage components at even multiples of the fundamental frequency — the 2nd, 4th, 6th and higher orders — that appear as asymmetric distortion in a three-phase power system. They behave differently from the familiar 3rd, 5th and 7th odd harmonics: balanced six-pulse rectifiers do not generate them, but asymmetry does. Half-controlled bridges, DC-off...
High THDi — total harmonic distortion of current — is the ratio of the RMS value of all current harmonics to the fundamental current, expressed as a percentage. It rises when nonlinear loads such as variable frequency drives (VFDs), rectifiers, UPS units and chargers draw current in pulses instead of a clean sine wave. A high reading must be explained, not simply cleared: measure the s...
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