Nord Drivesystems SK 180E Series, User Manual

Page: 41 / 212

2 Assembly and installation
BU 0180 en-4118 41
2.3 Braking resistor (BW)
- (from size 2)
During dynamic braking (frequency reduction) of a three-phase motor, electrical energy is returned to
the inverter if necessary. From size 2 and above , an internal or external braking resistor can be used
to avoid a shut-down of the device due to overvoltage. With this, the integrated brake chopper
(electronic switch) pulses the link circuit voltage (switching threshold approx. 420 V / 720 V
DC
,
depending on mains voltage) into the braking resistor. The braking resistor converts excess energy
into heat.
CAUTION
Hot surfaces
The braking resistor and all other metal components can heat up to temperatures above 70°C.
• Danger of injury due to local burns on contact.
• Heat damage to adjacent objects
Allow sufficient cooling time before starting work on the product. Check the surface temperatures with suitable
measuring equipment. Maintain an adequate distance to adjacent components or provide protection against
contact.
2.3.1 Internal braking resistor SK BRI4-…
The internal braking resistor can be used if only slight, short
braking phases are to be expected.
Similar to illustration
• The braking resistor cannot be retrofitted and must therefore be taken into account in the order.
• The output power of the braking resistor is limited and can be calculated as follows.
)² ) / 30 ( 1 ( * tbrems Pn P + =
, however, the following applies P < P
max
– (P=Brake power (W), P
n
= Continuous brake power of resistor (W), P
max
. peak brake power, t
brake
= duration
of braking process (s))
– (For details of P
n
and P
max
see

Section 0 "Electrical data")
• The permissible continuous brake power P
n
must not be exceeded in the long-term average.
• The peak and continuous powers must be limited by adjusting the parameter settings.
Required parameter settings
A braking resistor is installed by default in certain versions of the device. As delivered, the relevant
parameters for limitation of the peak and continuous powers are pre-set (refer to the following tables).