Why Variable Frequency Drives Cause Harmonic Distortion Variable frequency drives are widely used in modern factories. They control motor speed, improve process control, and make many systems more energy efficient.However, variable frequency drives also create harmonic distortion.The problem comes from the way variable frequency drives draw current from power supplies. They do not draw curr...
How Variable Frequency Drives Create Power Quality Problems Variable frequency drives (VFDs) are widely used in modern industrial systems because they improve motor control, reduce energy consumption, and increase production efficiency. However, as more facilities install VFD systems, VFD power quality problems are becoming a major concern. A variable frequency drive is a nonlinear load that chang...
Medium Voltage Harmonic Filters: A Complete Selection Guide Medium voltage harmonic filters help industrial facilities, renewable energy plants, utilities, and infrastructure projects control harmonic distortion in their electrical systems. Harmonics can reduce power quality, increase equipment losses, create overheating, and interfere with normal system operation. A correctly designed harmonic fi...
Installing a capacitor bank should improve power factor, reduce reactive power demand and release capacity in transformers and cables. However, some facilities find that their power factor remains below the utility target even after the capacitor bank has been commissioned. This does not necessarily mean the capacitor bank is defective. The cause may be incorrect sizing, changing loads, harmonic d...
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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