Applying Drives to Single-Phase Input Application
Figure-2 Typical Single-Phase Configuration
12.2 Power(HP), Input Current and Output Current
When using a three-phase VFD with single-phase input, derating the drive’s output current
and horsepower will be necessary because of the increase in DC bus ripple voltage and
current. In addition, the input current through the remaining two phases on the diode bridge
converter will approximately double, creating another derating consideration for the VFD.
Input current harmonic distortion will increase beyond that with a three-phase supply
making the overall input power factor low. Input current distortion over 100% is likely under
single-phase conditions without a reactor. Therefore, the reactor is always required. When
using a motor that is selected by the three-phase drive rating criteria when using single-
phase input, it may result in poor performance, premature drive failure. The selected drive
of single-phase current ratings must meet or exceed the motor current rating.
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