Operation Principle And Hardware Description; Contents Of This Chapter; Operation Principle - ABB ACS880-304 +A018 Hardware Manual

Operation principle and hardware description 19

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Operation principle and
hardware description

Contents of this chapter

This chapter contains a description of the diode supply unit. The information is valid for the
units with ACS880-304 +A018 diode supply modules.

Operation principle

The heart of the diode supply unit is a diode-thyristor bridge. It rectifies three-phase AC
current to direct current for the intermediate DC link of the drive. The intermediate DC link
supplies the inverter that run the motor. There can be one inverter unit only (single drives)
or several inverter units (multidrives) connected to the intermediate circuit. The DSU
modules have inbuilt AC chokes. The AC chokes smoothen the current waveform in the
power supply network and voltage in the DC link of the drive.
The main difference between the ordinary diode-diode bridge and the controlled diode-
thyristor bridge is the controllability. You cannot control the operation of the diodes but you
can control the thyristors: thyristor can be kept blocked or controlled conductive in forward
direction. By controlling the thyristors, you can limit the AC current of the drive at the
power up without additional charging circuit in the supply unit or in inverter units.