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

7.2

Braking resistors

7.2.1

Description

The excess energy of the DC link 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 heat loss from the Line Modules or
Motor Modules to be dissipated. This reduces the level of air conditioning required.
Resistors with rated powers of 25 kW and 50 kW are available.
Greater outputs can be implemented by connecting Braking Modules and braking resistors in
parallel. In this case, the Braking Modules are installed in the air duct of the Line Modules and
Motor Modules. Depending on the size of the respective module, up to three mounting
locations are available.
Since the braking resistors can be used in converters with a wide voltage range, the voltage
can be adjusted (for example, to reduce the voltage stress on the motor and converter) by
setting the response thresholds on the Braking Module.
A thermostatic switch monitors the braking resistor for overtemperature and issues a signal
on a floating contact if the limit value is exceeded.
7.2.2

Safety information

Not observing fundamental safety instructions and residual risks
Not observing fundamental safety instructions and residual risks listed in Chapter 1 can
result in accidents with severe injuries or death.
• Comply with the fundamental safety instructions.
• When assessing the risk, take into account remaining risks.
Fire due to overheating when the total length of the connecting cables is exceeded
Excessively long Braking Module connection cables can cause components to overheat with
the associated risk of fire and smoke.
• The Braking Module connecting cables may not be longer than 100 m.
Air-cooled chassis power units
Equipment Manual, 06/2020, 6SL3097-5AE00-0BP3
WARNING
WARNING
DC link components
7.2 Braking resistors
353