Short-Circuit Protection And Fuse Coordination - Siemens sirius System Manual

8.7.2 Short-circuit protection and fuse coordination

Coordination type 1
Coordination type 2
Maximum short-circuit
current
Motor feeder:
coordination type 1
Motor feeder:
coordination type 2
Comparison of coordi-
nation types 1 and 2
SIRIUS System Manual
GWA 4NEB 430 0999-02b
IEC 60947-4-1/DIN VDE 0660 Part 102 draws a distinction between two
coordination types, known as coordination type 1 and coordination type 2. In
both coordination types, the short circuit to be dealt with is reliably discon-
nected. The differences lie only in the degree to which the device is dam-
aged after a short circuit.
The motor feeder can be operable after each short-circuit disconnection.
Damage to the soft starter is possible. The circuit breaker itself always
attains coordination type 1.
After a short-circuit event there must be no damage to the soft starter or
any other switching device; only the backup fuse may be destroyed. The
actual motor feeder can be put into operation again immediately once the
short circuit fuse has been replaced.
All the specified fuse configurations are designed for a maximum short-cir-
cuit current of 50 kA. This ensures that short circuits of 50 kA can be dis-
connected without posing a threat to persons or the system.
Note on configuration
A fuseless configuration is recommended for motor feeders (i.e. the combi-
nation of a 3RV circuit breakers and a 3RW30 soft starter). Coordination type
1 is thus attained.
To set up a motor feeder of coordination type 2, the feeder must be fused
(i.e. the motor must be provided with overload protection).
The following can be used:
• The 3NE1 all-range fuse, which unifies line protection and semiconductor
protection
• The 3NE8 semiconductor protection fuse, in which case additional protec-
tion must be provided for the line
The configuration variant on the basis of coordination type 2 is associated
with higher costs than that of coordination type 1, which is why the fuseless
configuration (coordination type 1) is recommended. The advantages are:
• Fewer components in the cubicle
• Less effort required for wiring
• Less cubicle space required
• Lower price
3RW3 semiconductor motor control unit
8-45