Motor Capacitors

Capacitors improve power factor near the motor by providing much of the reactive current demanded by the motor. Thus, this reactive current does not flow from the electric utility provider through the facility protective devices and distribution wiring. This results in less heat dissipation and lower kilowatt wiring losses that can be calculated based on the National Electrical Code Handbook, Chapter 9 Table 9. Kilowatt losses through wire splices and protective devices such as motor starters, fused-disconnect switches and breakers can be even greater than wiring losses. The percentage of kilowatt-hour savings increases as motor load decreases since motor power factor drops significantly when load is below 60%-70% of motor nameplate rating. Thus, energy savings can be achieved even on high efficiency motor applications. Kilowatt-hour energy savings of 5 to 10% or more are possible, particularly for lightly-loaded motors, and quick paybacks are typical.
Also, many electric utilities add an additional charge to customer electric bills if facility power factor is lower than a minimum, as defined by the utility company tariff. Adding motor capacitors raises facility power factor and reduces or eliminates this utility penalty based on the amount of reactive power (kilovars) added by the capacitors. Considering this tariff avoidance alone can often result in paybacks of 12 to 24 months. With the combined energy savings and power factor penalty avoidance, the resulting paybacks that can be less than 12 months. Additionally, capacitors raise voltage at the motor, typically by about 1%, and have a smoothing affect on power quality irregularities.

Motor Capacitors provide the following benefits:

• Reduces kilowatts (power demand)
• Reduces kilowatt-hours (energy)
• Reduces utility power factor penalty charges
• Improves motor voltage and smoothes out power quality variations
• Typically have a 1 year warranty and a life of about twenty years