Braking Resistor; Description; Safety Information - Siemens SINAMICS S120 Equipment Manual

5.7.6

Braking resistor

5.7.6.1

Description

The regenerative energy of the drive line-up is dissipated via the braking resistor. The
braking resistor is connected to a Braking Module. The braking resistor is positioned outside
the cabinet or switchgear room. This enables the resulting heat loss to be dissipated, thereby
reducing the amount of air conditioning required.
A thermostat monitors the braking resistor for overheating and, if the limit value is exceeded,
it is signaled via a floating contact. The tripping temperature is 120 °C; this corresponds to a
surface temperature on the resistor elements of approximately 400 °C.
Only one braking resistor may be connected to a Central Braking Module.
The power of the braking resistors is matched to the rated braking power of the Central
Braking Modules; however, operation is restricted to a reduced duty cycle of 15 seconds
every 20 minutes.
The thermostat contact must be wired at the plant end so that evaluations can be carried
out in the CU320 or in a higher-level controller; see the section titled "Configuring the
overtemperature checkback".
5.7.6.2

Safety information

The surface temperature of the braking resistors may exceed 80 °C.
CAUTION
A cooling clearance of 200 mm must be maintained on all sides of the component (with
ventilation grilles).
The braking-resistor cables must be laid in such a way that they are short-circuit and
ground-fault proof.
NOTICE
A maximum cable length of 300 m is permissible between the Central Braking Module and
the braking resistor.
S120 Cabinet Modules Equipment Manual
Manual, (GH5), 10/2008, A5E00427098A
WARNING
CAUTION
Cabinet Modules
5.7 Central Braking Modules
215