Power Factor
(Commercial and Industrial)

What is Power Factor?
Electrical inductive loads from items like motors, transformers and magnetic ballasts carry real power (measured in kilowatts, kw) and reactive power (measured in kilovolt-amperes reactive, kvar). Real power does the "productive" work. Reactive power generates the magnetic field required for inductive devices to operate. The total, or apparent power (measured in kilovolt-ampere, kva) is the vector sum of the two.

If the circuit is purely resistive, the power factor is 100 percent. As the amount of inductive load increases, the power factor decreases. One of the most common and economical means of improving power factor is by using capacitors.

Because power factor correction capacitors generate the reactive (magnetizing) power (kvar) required by inductive loads locally, this magnetizing current doesn't have to be produced by PSNH, or by your own distribution system. This greatly improve efficiency, for example:

A typical 10 HP three-phase motor, operating at 230 volts with a power factor of 87 percent, draws 23.8 amps. The utility and customer equipment must carry 23.8 amps of line current. A portion of this current is used to magnetize the motor.

A 3-kvar capacitor supplied at the motor would provide approximately 7.5 amps of magnetizing current. Therefore, utilizing the power triangle, only 21.1 amps are needed from the source. The resulting power factor is 98 percent.

Where are capacitors installed?

Capacitors may be installed in a variety of locations depending on the purpose of the installation. Installation at the Motor Starter (C1) provides the best control and greatest loss reduction, but may not be the best economic consideration. Installing a bank of capacitors at a Motor Control Center (C2), or on the Secondary (C3) or Primary (C4) side of the transformer may result in a lower cost per kvar of capacitors, but may not provide the control or increase in system capacity desired.

How correcting power factor can save money

The PSNH demand charge is based upon kva demand for LG customers and upon 80 percent of the kva demand for GV (Commercial and Industrial) customers who have a power factor of less than 80 percent. Power factor correction may offer a savings opportunity for some customers.
Depending on the method and location of power factor correction, improved power factor may also free up capacity on your transformer and plant electrical distribution system.

Other means of improving power factor:

Take these measures to improve energy efficiency, and power factor.

• Properly size motors
  
• Use energy efficient motors
  
• Install variable speed drives that use pulse-width modulation technology
  

How can PSNH help?
PSNH is here to help you evaluate the benefits of power factor correction for your facility. We can also aid in sizing and locating the appropriate capacitors to best meet your needs.
For more information, call your PSNH Account Executive.