ABB DCS 600 MultiDrive Series Manual page 17

Insulated DC
drive, 12 – pulse
serial /sequential
configuration
Monitoring of second
earth fault
DCS 600 Manual for 12 – Pulse Operation
Of course one of the two 3 – phase systems can be supervised.
Then the DC circuit and the other AC system are simultaneously
supervised only if both converters are active. However, it is more
logical to connect the insulation monitor with the motor as shown in
because the DC circuit is the centre of symmetry of the
Fig.2/10
whole power circuit. Furthermore, the risk of an insulation fault is
higher in the motor than in the converters or in the transformer.
is the synopsis of an insulated DC drive in a 12 – pulse
Figure 2/11
serial configuration with two thyristor power converters and one
motor, with a dedicated power transformer and with one insulation
monitor unit type IRDH from BENDER.
In this case it is obvious that the insulation monitor unit must be in-
stalled at the DC side.
The second earth fault in isolated networks (IT) is monitored by an
earth fault transformer in each leg.
for second earth fault monitoring in 12 – pulse serial configurations:
Chapter 2 – Twelve–Pulse Technology
(L/+)
INSULATION
0
MONITOR
(L/-)
shows an example
Figure 2/12
(L/+)
INSULATION
0
MONITOR
(L/-)
Rm
Rm
KE
IRDH
Figure 2/11
Rm
Rm
KE
IRDH
Figure 2/12
2 - 9
II F2