Hawkins Electrical Guide v. 05 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

Ans. When the phase difference is due to an excess of capacity.

EXAMPLE.—A circuit having a resistance of 3 ohms, and a resultant reactance of 4 ohms, is connected to a 100 volt line. What is: 1, the impedance, 2, the current, 3, the apparent power, 4, the angle of lag, 5, the power factor, and 6, the true power?

1. The impedance of the circuit.

Z = √(3² + 4²) = 5 ohms.

2. The current.

current = volts ÷ impedance = 100 ÷ 5 = 20 amperes.

3. The apparent power.

apparent power = volts × amperes = 100 × 20 = 2,000 watts.

4. The tangent of the angle of lag.

tan φ = reactance ÷ resistance = 4 ÷ 3 = 1.33. From table of natural tangents (page 451) φ = 53°.