CHAPTER
6 Using Power Factor to Determine Energy Efficiency
S
ooner or later, marine electricians and boatowners are confronted with the term
power factor. For work on small boats, power factor is usually not too much of a con-
cern, but as boats get bigger and bigger, with more AC-powered gear than ever
installed, it warrants careful consideration and perhaps even monitoring.
Warning: At 110 V or 240 V, AC power on boats—whether shore power or pro-
vided by AC generators and DC-to-AC inverters—is potentially lethal. If you are not
completely confident in your abilities around AC circuits, call in a specialist.Understanding Power Factor
What is power factor? One definition states it as: “The ratio of real power to apparent
power delivered in an AC electrical system or load. Its value is always in the range of 0.0 to
1.0 or 0% to 100%. A unity power factor (1.0) indicates that the current is in phase with
the voltage and that reactive power is zero.”
Hmmm. Everybody still with me? Let’s break that definition down a bit:- Factordescribes a proportional relationship between two quantities—in this case, real
power and apparent power. - Real power(also known as active powerorworking power) describes the amount of
electrical energy that is converted into useful work. - Apparent powerdescribes the total electrical energy actually delivered by the power
supply (i.e., a utility company, an AC generator, or a DC-to-AC inverter). - Reactive poweris the difference between the power delivered and the power converted
to useful work.
It may be helpful to think of power factor as the amount of current and voltage the
customer actually uses compared to what the utility supplies. A high power factor is con-
sidered to be 90% or more.
Copyright © 2007 by Edwin R. Sherman. Click here for terms of use.