Question

The meter constant of a single-phase, 230 V induction watt-meter is 600 rev/kW-h. The speed of the meter disc for a current of 15 A at 0.8 power factor lagging will be?

(a) 30.3 rpm

(b) 25.02 rpm

(c) 27.6 rpm

(d) 33.1 rpm

The question was asked in an interview.

I need to ask this question from Advanced Problems on Measurement of Power in Polyphase Circuit in portion Measurement of Power and Related Parameters of Electrical Measurements

Answer 1

Right choice is (c) 27.6 rpm

Best explanation: Meter constant = \(\frac{Number \,of\, revolution}{Energy} = \frac{600 × 230 × 15 × 0.8}{1000}\) = 1656

∴ Speed in rpm = \(\frac{1656}{60}\) = 27.6 rpm.