ABB ACQ800 Series, Hardware Manual

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ACQ800-37 Hardware Manual 33
The ACQ800-37
Operation principle
The line-side and motor-side converters have their own RDCU control units and
control programs. The parameters of each program can be viewed and changed
using one control panel. The converter to be controlled can be selected using the
control panel; see section
Controls below.
Line-side converter
The line-side converter rectifies three-phase AC current to direct current for the
intermediate DC link of the drive. The intermediate DC link is further supplying the
motor-side converter that runs the motor.
The line-side converter is an active unit that, together with an LCL (inductor-
capacitor-inductor) filter, enables low harmonic distortion at the input terminals of the
drive.
By default, the line-side converter controls the DC link voltage to the peak value of
the line-to-line voltage. The DC voltage reference can also be set higher by a
parameter. The control of the IGBT power semiconductors is based on the Direct
Torque Control (DTC) method also used in the motor control of the drive. Two line
currents and the DC link voltage are measured and used for the control.
AC voltage and current waveforms
The AC current is sinusoidal at a unity power factor. The IGBT supply unit does not
generate characteristic current or voltage overtones like a traditional 6- or 12-pulse
bridge does.
The Total Harmonic Distortion (THD) in voltage depends slightly on the Short Circuit
Ratio in the Point of Common Coupling (PCC). The high-frequency switching and
high du/dt slightly distort the voltage waveform at the input of the converter.
AC fuses LCL filter IGBT supply module
AC input Intermediate
DC link