Operation Principle; Simplified Main Circuit Diagram; Charging - ABB ACS880-207 Hardware Manual

14 Operation principle and hardware description

Operation principle

IGBT supply unit rectifies three-phase AC current to direct current for the intermediate DC
link of the drive. The intermediate DC link supplies the inverters that run the motors. There
can be one inverter unit only (single drives) or several inverter units (multidrives) connected
to the intermediate circuit.
The LCL filter is an essential part of the IGBT supply unit. The supply module does not work
without the filter. It suppresses the AC voltage distortion and current harmonics. The high
AC inductance smooths the line voltage waveform distorted by the high-frequency switching
of the converter. Capacitive component of the filter effectively filters the high-frequency (over
1 kHz) harmonics.

Simplified main circuit diagram

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The following figure shows the simplified main circuit diagram of the rectifier.
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1. AC voltage
2. AC fuses
3. LCL filter
4. IGBT supply module
5. DC fuses
6. DC voltage

Charging

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A charging circuit powers up the DC link capacitors of the drive system smoothly. Discharged
capacitors cannot be directly connected to the full supply voltage. The charging current
must be limited until the capacitors are charged and ready for normal use.
In cabinet-installed units, a resistive charging circuit consisting of fuses, a contactor and
charging resistors is used. The resistive charging circuit is in use after power-up as long as
DC voltage has risen to a predefined level.
The control program has a function for controlling the charging circuit. For further information,
see the firmware manual.
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