Posted by Electric motors:
Electric motors are everywhere in many modern industrial plants and factories, in some industries, there are comprising up to 80% of facilities’ electrical load and they also can be the cause of several types of power-quality problems commonly seen in these operations. These problems can include:
- Voltage sags can result in local or adjacent areas from the direct starting of large electric motors, either individually or in groups.
- Harmonics can be generated by saturation of the magnetic core of electric motors.
- Low power factor – at rates of 0.85 to 0.90 at full load, down to 0.35 at no-load – can be created by the reactive energy required by induction motors.
Variable speed drives:
Variable speed drives (VSDs) have become goto devices for facilities seeking to improve the efficiency of induction motors. Common applications include fans, pumps, and compressors. However, VSDs also has become a major source of harmonic distortion if they aren’t associated with a harmonic filtering solution.
Lighting systems:
Lighting typically represents between 5% and 8% of an industrial facility’s electrical load. Power-quality problems associated with this equipment can include:
- Harmonics, which can be caused by energy-efficient compact luminous lamps (CFLs).
- Low power factor resulting from luminous high-intensity discharge lamps and CFLs.
- Harmonic distortion and a power factor less than 1 also can be caused by gradually popular high-efficiency LED lighting.
Transformers:
Transformers are critical pieces of equipment in industrial plants, given the high volumes of electricity which will be moved around such facilities. They can also compromise power quality through such problems as:
- Harmonics resulting from capacity of their magnetic core.
- Low power factor, which can follow from their need for reactive energy. The reactive power absorbed by a transformer can total up to 5% of its rating at full load.
Capacitors:
Capacitors can create resonance which will amplify the magnitudes of harmonic voltages and currents. For this reason, a project-specific study should be done to properly size the reactive power compensation system. Moreover, capacitor-bank switching can cause small voltage transients, regularly with no impact on the system.
Uninterruptible Power Supplies (UPS):
Old-generation UPS were characterized by substantial harmonic distortion. In new generation UPS the entire harmonic alteration is reduced. However, attention should be paid to the high-frequency harmonics these devices may generate.
Office Equipment
Business and office equipment based on power electronics, such as PCs, copiers and printers, draw a non-sinusoidal current and are a source for harmonic alteration.
