Electrical Power Systems Technology

68 Electrical Power Systems Technology

electrical energy that is used must pass through a watt-hour meter. The
same type of system is used for home, industrial, or commercial service
entrances.
The operation of a watt-hour meter is, in many ways, similar to the
conventional wattmeter. A potential coil is connected across the incom-
ing power lines to monitor voltage, while a current meter is placed in se-
ries with the line to measure current. Both meter sections are contained
within the watt-hour meter enclosure. The voltage and current of the
power system affect the movement of an aluminum-disk rotor that is
part of the watt-hour meter assembly. The operation of the watt-hour
meter may be considered as similar to that of an AC induction motor.
The stator is an electromagnet that has two sets of windings—the volt-

Figure 3-6. Construction diagram of a watt-hour meter

Figure 3-7. Reading the dials of a watt-hour meter