Using a Single Phase Power Source
12
Using a Single Phase Power Source
12.1
Single Phase Rating
The SV-iS7 series inverter is a three-phase variable frequency drive (VFD). When applying single-
phase power to a three-phase VFD, there are several limitations that need to be considered.
The standard pulse-width-modulated (PWM) VFDs use a 6-pulse diode rectifier. The 6-pulse
rectification results in 360 Hz DC bus ripple when using a three-phase 60 Hz power supply.
However, when using a single-phase power source, the DC bus ripple becomes 120 Hz. The
input current and harmonics increase, and the VFDs DC bus circuit is subject to higher stress in
order to deliver equivalent power.
Input current distortion of 90% THD and greater can be expected under single-phase input,
compared to approximately 40% with three-phase input as indicated in Figure 2.
Therefore, use of a single-phase requires the three-phase VFD power rating to be reduced
(derated) to avoid over stressing the rectifier and the DC link components.
<Figure-1 Typical Three-Phase Configuration>
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