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**Power Factor** is a measure of how effectively electrical power is being used. A high power factor (approaching unity) indicates efficient use of the electrical distribution system while a low power factor indicates poor use of the system.

Many loads in industrial electrical distribution systems are ** inductive**.

Examples include motors, transformers, fluorescent lighting ballasts, and induction furnaces.

The line current drawn by an inductive load consists of two components:

The magnetizing current is the current required to sustain the electro-magnetic flux or field strength in the machine. This component of current createsMagnetizing Current

reactive powerthat is measured in kilovolt-amperes reactive (kVAR).Reactive powerdoesn’t do useful “work,” but circulates between the generator and the load. It places a heavier drain on the power source, as well as on the power source’s distribution system.

ThePower Producing Current

real(working)power-producing currentis the current that reacts with the magnetic flux to produce the mechanical output of the motor.is measured in kilowatts (kW) and can be read on a wattmeter.

Real Power

**Apparent Power **is the total of **Real ****(working) power and Reactive power** together. **Apparent power** is measured in kilovolt-amperes (kVA)

Power Factoris the ratio of real power to apparent power.

To determine power factor (PF), divide real power (kW) by apparent power (kVA).

**The Power Triangle
**In a sinusoidal system, the result is also referred to as the cosine.

Another way to visualize power factor and demonstrate the relationship between kW, kVAR and kVA, is the right “power” triangle.

The **hypotenuse **of the triangle represents the **apparent power **(kVA) which is simply the system voltage multiplied by the amperage times the square root of three (for a three-phase system) divided by 1,000.

The **right side **of the triangle represents the **reactive power** (kVAR).

The **base** of the triangle represents the **real or working power**, measured in kW. The angle between the kW and kVA legs of the triangle is the phase angle cosine.

**Power factor **is also referred to as **leading **or **lagging**. In the case of the magnetizing current, the power factor is lagging, in that the current follows the voltage waveform.

The amount of lag is the electrical phase angle between the voltage and the current. Power Factor is equal to the cosine of the phase angle between the voltage and current waveforms.

Excerpts taken from “Energy Management for Motor Driven Systems”, Office of Industrial Technologies, Energy efficiency and renewable energy, US Department of Energy, Chapter 8 Power Factor Correction

Other great resources are: the US Motor Challenge Fact Sheet, “Reducing Power Factor Cost”, a Program of the Department of Energy and Railcar and Power Triangle from Con Edison website