Braking Resistors; Pm Blocksize; Description Braking Resistors; Safety Instructions - Siemens S120 Instructions Manual

5 BRAKING RESISTORS

5.1

PM BLOCKSIZE

5.1.1

Description braking resistors

The PM340 Power Modules cannot regenerate into the line supply. For regenerative operation, e.g. the
braking of a rotating mass, a braking resistor must be connected to convert the resulting energy into heat.
A thermostatic switch monitors the braking resistor for overtemperature and issues a signal on an isolated
contact if the limit value is exceeded.
5.1.2

Safety instructions

WARNING
Risk of fire and device damage as a result of ground fault / short-circuit
The cables to the braking resistor must be routed so that a ground fault or short circuit can
be ruled out. A ground fault can result in fire.
• Comply with local installation regulations, which allow this fault to be ruled out.
• Protect the cables from mechanical damage.
• In addition, apply one of the following measures:
-
Using cables with double insulation.
-
Observe adequate clearances, e.g. through the use of spacers.
-
Route the cables in separate cable ducts or pipes.
CAUTION
Risk of burns or damage resulting from high surface temperature of the braking resistor
The braking resistor can become very hot. You can be severely burnt when touching the
surface. Neighboring components can become damaged.

Mount the braking resistor so that it cannot be touched. If this is not possible, at the dangerous
locations, attach an appropriate warning note that is clearly visible and easy to understand.

To avoid temperature-related damage to adjacent components, follow these rules:
For PM340 Power Modules:
-
Ensure a cooling clearance of 100 mm on all sides of the braking resistor
5-1