Electrical Engineering ⇒ Topic : Characteristics of Dynamometer Wattmeters

Characteristics of Dynamometer Wattmeters

It is worthwhile to give the advantages, disadvantages, errors, ratings and range extension of dynamometer wattmeters.

Advantages

(1) They can be used for the measurement of a.c. as well as d.c. power.

(2) They have uniform scale unlike dynamometer ammeters and voltmeters which have squarelaw scales.

(3) By careful design, high accuracy can be obtained.

Disadvantages

(1) At low power factors, the inductance of the potential coil causes serious en-ors.

(2) The readings of the instrument may be affected by stray magnetic fields. In order to prevent it, the instrument is shielded from the external magnetic fields by enclosing it in a soft-iron case.