ABB DSMB127 57360001-HG memory board, RWM with battery
the nominal value, the capacitors in the phase
modules of the INU start to discharge as well.
Grounding switch
The grounding switch enables safe access to the
DFE - INU compartment of the drive.
When the switch is in position grounded, DFE (1),
DC link (2), INU (3) and output filter (4) of the drive
are connected to the PE ground bus (5).
The switch is electromechanically interlocked with
a discharge monitoring circuit to prevent closing
of the switch when the DC link is still charged.
Grounding the drive is only possible after the main
power supply has been disconnected and the DC
link has discharged.
When the voltage is below 50 V (DC), press the
pushbutton Grounding Switch Unlocked (1)
located on the control compartment door (the
pushbutton lights up) and - at the same time - turn
the grounding switch to the grounded (2) position.
When the grounding switch is in position
grounded, the door safety switch of the DFE-INU
compartment is released and the door can be
opened.
2.3.3 INU - Inverter unit
The INU converts the DC voltage to the required AC
motor voltage and frequency. The unit is com posed of three identical phase modules, one phase
module per phase U, V and W. The size of the phase
modules depends on the power rating of the drive.
The arrangement of the phase modules in the cabi net is the same for all drives.
For information on the dimensions and the weight,
see 10.6.13 Replacing a phase module.

The active 3-phase unit is designed as a self-com mutated, 5-level voltage source inverter. As a result
of the multi-level topology, the drive produces an
optimum number of switching levels - nine levels,
phase to phase.
The resulting waveforms permit the application of
standard motors.
2.3.4 EMC and sine filter
Depending on the application, the drive is
equipped with one of the following filters at the
output of the inverter:
• EMC filter (1)
• Sine filter (2)
2.3.5 Terminal compartment
The terminal compartment is located behind the
swing frame of the control unit. The compartment
provides the terminals for the feeder and motor
cables, and the ground bus for the termination of
the ground cable and the cable screens.