154 Electrical Power Systems Technology
Sample Problem:
Given: a power line frequency of 60 hertz is applied to an electric
motor.
Find:
- fundamental frequency
- 3rd harmonic
- 5th harmonic
- 7th harmonic
Solution:
- fundamental = 60 Hz
- 3rd harmonic = 60 × 3 = 180 Hz
- 5th harmonic = 60 × 5 = 300 Hz
- 7th harmonic = 60 × 7 = 420 Hz
GENERATOR VOLTAGE REGULATION
As an increased electrical load is added to an alternator, it tends to
slow down. The decreased speed causes the generated voltage to de-
crease. The amount of voltage change depends on the generator design
and the type of load connected to its terminals. The amount of change in
generated voltage from a no-load condition to a rated full-load operating
condition is referred to as voltage regulation. Voltage regulation may be ex-
pressed as:
VNL – VFL
VR = ————— × 100
VFL
where:
VR = the voltage regulation in percent,
VNL = the no-load terminal voltage, and
VFL = the rated full-load terminal voltage.
Sample Problem:
Given: a single-phase alternator has a no-load output voltage of
122.5 volts and a rated full-load voltage of 120.0 volts.
Find: the voltage regulation of the alternator.
Solution: