NORD Drivesystems BU0750 - Manual (Page 22)

NORDAC SK 750E Manual
22 Subject to technical amendments BU 0750 GB-3311
2.9.1 Mains supply (PE, L1, L2, L3)
No special safety devices are required on the mains input side for the frequency
inverter, the use of the normal mains protection (see 9 Technical Data) and a
master switch or contactor is recommended.
Note:
Use of this frequency inverter on an IT network is possible after minor
modifications. Please consult your supplier.
2.9.2 Electromagnetic brake (+Br, -Br, PE)
An output voltage is generated by the frequency inverter at the terminals
-Br/+Br to actuate an electromechanical motor brake (see Section 2.9,
Electrical connections to the power unit).
This depends on the supply voltage present in the frequency inverter. The
assignment is as follows:
Mains input voltage (AC) Brake coil voltage (DC)
400V ~ 180V =
460V ~ ... 480V ~ 205V =
230V ~ 105V =
Note: The allocation of the correct brake or brake coil voltage must be
taken into account in the design with reference to the mains
voltage of the frequency inverter.
2.9.3 Brake resistor (+B, -B, PE)
During dynamic braking (frequency reduction) of a three-phase motor,
electrical energy is returned to the inverter. In order to avoid overcurrent
switch-off of the frequency inverter, the integrated brake chopper can convert
the returned energy into heat by connection of an external braking resistor.
The connection for the frequency inverter → brake resistor should be
shielded and as short as possible.
Switching of this connection must only be made when no voltage is present!
Note:
The possible generation of large amounts of heat in the braking
resistor must be taken into account.
2.9.4 Motor cable (U, V, W, PE)
The motor cable maximum length of 150m (Please note also Section 10.5 EMC
limit value classes). If a shielded motor cable is used, or the metallic cable duct is
well earthed, the maximum length of 50m should not be exceeded. For longer
cable lengths, the frequency inverter can be equipped with an optional internal
motor filter (at extra charge).
Switching (contactor or motor protection switch) at the output (U, V, W), is not
permitted while the frequency inverter is delivering current!
Note: For multiple motor operation the total cable length consists of the sum
of the individual cable lengths. If the sum of the cable lengths is too
large, an optional internal motor filter should also be ordered.