296 Electrical Power Systems Technology
trial plants, power demand control systems and procedures can help in-
crease the efficiency of our nation’s electrical power systems.
Be careful not to confuse the load factor of a power system with the
power factor. The power factor is the ratio of power converted (true pow-
er), to the power delivered to a system (apparent power). If necessary, you
should review power factor (see Chapter 2).
Most industries use a large number of electric motors; therefore, in-
dustrial plants represent highly inductive loads. This means that industrial
power systems operate at a power factor of less than unity (1.0). However,
it is undesirable for an industry to operate at a low-power factor, since the
electrical power system will have to supply more power to the industry
than is actually used.
A given value of volt-amperes (voltage × current) is supplied to an
industry by the electrical power system. If the power factor (pf) of the in-
dustry is low, the current must be higher, since the power converted by
the total industrial load equals VA × pf. The value of the power factor de-
creases as the reactive power (unused power) drawn by the industry in-
creases. This is shown in Figure 11-2. We will assume a constant value of
true power, in order to see the effect of increases in reactive power drawn
Figure 11-2. Effect of increases in reactive power
(VAR) on apparent power (VA)