2-26
H Countermeasures against Harmonics
With
the continuing development of electronics, the
generation of harmon
-
ics from industrial machines has been causing problems recently.
The
Ministry of International T
rade and Industry provided some guidelines
in
September 1994 for the suppression of harmonics from electrical house
-
hold
appliances and electrical equipment in
Japan. Since then, the prob
-
lem has been drawing considerable attention.
Refer
to the following information for the definition of
harmonics (i.e., har
-
monic currents with voltages) and countermeasures against the genera-
tion of harmonics from the Inverter.
D Harmonics
Definition
Harmonics consist of electric power produced from AC power and alternating at fre-
quencies that are integral multiples of the frequency of the AC power.
The
following frequencies are harmonics of a 60- or 50-Hz commercial power supply
.
Second harmonic:
120 (100) Hz
Third harmonic:
180 (150) Hz
Second harmonic (120 Hz)
Basic frequency (60 Hz)
Third harmonic (180 Hz)
Problems Caused by Harmonics Generation
The
waveform of the commercial power supply will be distorted if the commercial power
supply
contains excessive harmonics. Machines with such a commercial power supply
will malfunction or generate excessive heat.
Basic frequency (60 Hz) Third harmonic (180 Hz)
Distorted current wave
form
Design Chapter
2
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