70 Electrical Power Systems Technology
fore, a power factor of less than 1.0 will be indicated. The scale must be
calibrated to measure power factor ranges from zero to unity.
Power-demand Meters
Power-demand monitors are instruments used to perform an impor-
tant industrial function. Power demand is expressed as:
peak power (kW)
power demand = ————————————
average power used (kW)
Figure 3-8. Using single-phase wattmeters to measure three-phase power: (A)
Two-wattmeter method; (B) Three wattmeter method