Application Note - Correcting unbalanced current and voltage with PowerLogic AccuSine

[Sreemant_Roy]

Unbalance is listed as one of the possible power quality problems that are common in an electrical distribution system. Even so, it is often overlooked and can damage electrical components. This Application Note reviews the causes and effects, and describes possible solutions for, unbalanced current or voltage in electrical networks.

On a related topic check out this US DoE paper - Eliminate Voltage Unbalance

Voltage unbalance is probably the leading power quality problem that results in motor overheating and premature motor failure. If unbalanced voltages are detected, a thorough investigation should be undertaken to determine the cause. Energy and cost savings occur when corrective actions are taken.

Voltage Unbalance Energy Savings Example

Assume that the 100-hp motor tested as shown in Table 1 was fully loaded and operated for 8,000 hours per year (hrs/yr), with an unbalanced voltage of 2.5%. With energy priced at $0.08/kilowatt-hour (kWh), the annual energy and cost savings after corrective actions are taken are: 

Annual Energy Savings = 100 hp x 0.746 kW/hp x 8,000 hrs/yr x (100/93 – 100/94.4) = 9,517 kWh
Annual Cost Savings = 9,517 kWh x $0.08/kWh = $760

Overall savings may be much larger because an unbalanced supply voltage may power numerous motors and other electrical equipment.