nord NORDAC SK 5xxE Series - DC-Coupling and Braking Resistor Connection

NORDAC SK 5xxE Manual
28 Subject to technical alterations BU 0500 GB
2.8.5 Braking resistor connection (X2 - +B, -B)
In drive engineering, DC-coupling is advisable if motors act as drivers and generators at the same time in the
system. Here, the energy from the drive which is acting as a generator can be fed back to the drive which is
acting as a motor. The advantages are lower energy consumption and the sparing use of braking resistors.
Note: In the 115V devices (SK 5xx-xxx-112-O, no DC terminal is provided. DC-coupling is therefore not
possible.
However, the following points must be taken into account:
(1) Use a connecting cable between the equipment, which is as short as possible.
(2) 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.
(3) Ensure that the coupling is disconnected as soon as one of the devices is no longer ready for operation.
(4) For a high availability a braking resistor (possibly lower power) must be used.
(5) 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.
Diagram of a DC-coupling:
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
Couplin
g
if
FIs ready
Readiness
message from
all FIs
U
1
U2