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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