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Appendix A. Single-phase Application | IED-S
A-1
Appendix A.
Single-phase Application
A.1 Introduction to the Application of Drives and Single-phase Power
System
When applying single-phase power system to three-phase drives, you must consider the following
restrictions. Standard pulse-width modulation (PWM) drives use 6-pulse diode rectifiers, which enables
simple structure and low cost. The 360Hz ripple DC bus used in the 6-pulse rectifier unit can be used
with the three-phase 60Hz, as shown in Figure A.1-1. However, under the single-phase power input,
the ripple of DC bus becomes 120Hz, which means the DC bus circuit of the drive needs to provide
equivalent power due to higher voltage. Moreover, comparing the single-phase input current and
harmonics with three-phase input, the distortion of the single-phase input current is 90% THD and the
three-phase input is about 40%, as shown in Figure A.1-2. Therefore, when using single-phase input,
it is necessary to reduce the rated capacity of the three-phase drive to avoid over-voltage of the rectifier
and DC components.
Figure A.1-1
Figure A.1-2
Rectifier