Omron SYSDRIVE 3G3JV Series User Manual page 35

Design
Causes of Harmonics Generation
Usually, electric machines have built-in circuitry that converts commercial AC power
supply into DC power.
Such AC power, however, contains harmonics due to the difference in current flow be-
tween DC and AC.
Obtaining DC from AC Using Rectifiers and Capacitors
DC voltage is obtained by converting AC voltage into a pulsating one-side voltage with
rectifiers and smoothing the pulsating one-side voltage with capacitors. Such AC cur-
rent, however, contains harmonics.
Inverter
The Inverter as well as normal electric machines has an input current containing har-
monics because the Inverter converts AC into DC. The output current of the Inverter is
comparatively high. Therefore, the ratio of harmonics in the output current of the Invert-
er is higher than that of any other electric machine.
A current flows into the
capacitors. The current
is different from the
voltage in waveform.
Voltage
Rectified
Voltage
Smoothed
Voltage
Current
Chapter 2
Time
Time
Time
Time
2-27