Electrical Engineering ⇒ Topic : Wattmeters

Wattmeters

A wattmeter, as its name implies, measures electric power given to or developed by an electric apparatus or circuit. A wattmeter is hardly ever required in a d.c. circuit because power (P = VI) can be easily determined from voltmeter and ammeter readings. However, in an a.c. circuit,such a computation is generally *speaking impossible. It is because in an a.c. circuit, power (P = VI cos Φ) depends not only on voltage and current but also on the phase shift between them.Therefore, a wattmeter is necessary for a.c. power measurement. There are two principal types of wattmeters viz.,

1. Dynamometer wattmeter             -        for both d.c. and a.c. power
2. Induction wattmeter                     -        for a.c. power only