Applying Drives to Single-Phase Input Application
12 Applying Drives to Single-Phase Input
Application
12.1 Introduction
LSLV-S100 is a three-phase standard variable frequency drive(VFD). When applying
single-phase power to a three-phase VFD, there are several constraints that need to be
considered. Standard Pulse-Width-Modulated (PWM) VFDs use a 6-pulse diode rectifier.
The 6-pulse rectification results in 360 Hz DC bus ripple when used with a three-phase 60
Hz supply.
However, under single-phase use, the DC bus ripple becomes 120 Hz and the VFDs DC
bus circuit is subject to higher stress in order to deliver equivalent power.
Additionally, input currents and harmonics increase beyond those encountered with three-
phase input.
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, single-phase use requires the three-phase VFD power rating be reduced
(derated) to avoid over stressing the rectifier and DC link components.
Figure-1 Typical Three-Phase Configuration
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