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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