3RW3 semiconductor motor control unit
SIRIUS System Manual
GWA 4NEB 430 0999-02b
8-45
8.7.2 Short-circuit protection and fuse coordination
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.
Coordination type 1
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.
Coordination type 2
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.
Maximum short-circuit
current
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.
Motor feeder:
coordination type 1
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.
Motor feeder:
coordination type 2
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
Comparison of coordi-
nation types 1 and 2
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
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