NORD Drivesystems BU0505 - Manual (Page 43)

2 Assembly and installation
BU 0505 GB-1013 43
M
3~
PE U V W +B -B -DC
PE L3 L2 L1
L1 / L
L2 / N
L3 / -
PE
M
3~
PE U V W +B -B -DC
PE L3 L2 L1
Coupling if
FIs ready
Readiness
message from
all FIs
U1
U2
Fig. 6 Diagram of a DC-coupling
1 The link circuits of the individual frequency inverters must be protected with suitable fuses.
2 The frequency inverters only obtain their power supply via the link circuit. Electrical isolation is
carried out via the power circuit breakers which must be provided in the supplies to the devices.
3 CAUTION! Ensure that the coupling is only made after readiness is reported. Otherwise, there
is a danger that all the frequency inverters will be charged by a single one.
4 Ensure that the coupling is disconnected as soon as one of the devices is no longer ready for
operation.
5 For a high availability a braking resistor must be used. If different sizes of frequency inverters
are used, the braking resistor must be connected to the larger of the two frequency inverters.
6 If devices with the same rating (identical type) are coupled, and the same mains impedances
are in effect (identical lengths of cable to the mains rail), the frequency inverters may be
operated without mains chokes. Otherwise a mains choke must be installed in the mains cable
of each frequency inverter.