Overcurrent Protection - Siemens SINUMERIK 840D sl Manual

Connection of the Components
5.6 Electronics Power Supply
5.6.6

Overcurrent protection

On the primary side and on the secondary side of the power supply device, devices and
cables must be protected from over-current using suitable protection devices.
Primary side
Recommended circuit-breakers (IEC 898) in the suppy cable can be found in the technical
data of the SITOP devices in the KT 10.1 catalog. The cable cross-section must be
considered.
The primary protection is performed by the device protection of the SITOP power supply and
also the line protection between the protective device and the power supply.
Secondary side
For the protection of the secondary side, particular attention must be paid to:
● Loading due to loads, possibly the simultaneity factor in response to machine operation
● The current carrying capacity of the cables in normal operation and in a short-circuit
● The ambient temperature
● Cable bundling (e.g. laying in a common duct)
● Cable laying method to EN 60204-1
EN 60204-1, Section 14, can be used to determine the overcurrent protection devices.
Protection of the load feeders
Load feeders must be protected selectively. Circuit-breakers are suitable (order no.: 5S...,
ETB1 catalog) or the SITOP select diagnostic component (order no.: 6EP1961-2BA00).
Configuration details for the secondary protection of the load feeders are contained in the KT
10.1 catalog (SITOP Power Supplies, "Technical Information and Configuration Notes"
section).
The rated size of the protective devices depends on the current need. The protection device
also performs the line protection and sometimes also the device protection of the attached
consumers. In a fault situation, the used power supply must be able to supply the required
power until being controlled.
Regulated power supplies (such as SITOP power) must be provided with an integrated
electronic short-circuit protection in accordance with EN 60204-1 which in the case of
overload/short-circuit, independently protects the SITOP power and the supplied 24 VDC
circuits against overload.
5-48
situation
Guide for the SINUMERIK 840D sl machine configuring
Manual, 07/2006 Edition, 6FC5397-6CP10-0BA0