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

5.7.7

Braking resistor

5.7.7.1

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 connected on the plant side so that the signal can be
evaluated in the Control Unit or in a higher-level controller; see the section titled
"Configuring the overtemperature checkback signal".
5.7.7.2

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).
CAUTION
The cables for the braking resistor must be routed to prevent short-circuits and ground
faults in accordance with IEC 61800-5-2:2007, Table D.1.
This can be accomplished, for example, by:
• Eliminating the risk of mechanical damage to the cables
• Using cables with double insulation
• Maintaining adequate clearance, using spacers, for example
• Routing the cables in separate cable ducts or tubes
Cabinet Modules
Manual, (GH5), 05/2010, A5E03263538A
WARNING
CAUTION
Cabinet Modules
5.7 Central Braking Modules
223