Electrical connection
6.2 Protecting the inverter
Installation and Operating Instructions SINAMICS G180
92
Operating Instructions, 02/2019, 4BS0751-007
6.2
Protecting the inverter
When protecting the inverter a distinction must be made between the two cases.
Procedure when the motor has approximately the same rating as the inverter (I
mot
≥
0.5 * I
fu
)
●
Protect the inverter against short-circuits.
●
Take the fuse value from the technical data or, using the inverter continuous input current
stamped on the type plate, select the next larger gL fuse.
●
Locate a gL fuse or circuit breaker upstream from the inverter.
●
In the case of the circuit breaker, set the thermal release to 1.2x the inverter continuous
input current as stamped on the type plate and the magnetic release to the lowest
possible value, between 1.5 and 2x the value of the inverter continuous input current.
–
Only use circuit breakers without time grading (time discrimination).
–
The break time of the circuit breaker in the case of a short circuit must be less than
8 ms.
Procedure when the motor has a significantly lower rating than the inverter (I
mot
< 0.5 * I
fu
)
●
Protect the inverter against short-circuits.
●
Dimension the fuse value as follows: I
fuse
< 2 * I
mot
. Use the next lower standard fuse
value than calculated.
●
Parameterize the inverter parameter P-INVERTER DATA/I contin. as a maximum to the
fuse value.
●
Locate a general line fuse or circuit breaker upstream from the inverter.
●
In the case of the circuit breaker, set the thermal release to 2x the rated motor current
stamped on the type plate and the magnetic release to the lowest possible value,
between 1.5 and 2x the value of the inverter continuous input current.
–
The break time of the circuit breaker in the case of a short circuit must be less than
8 ms.
6.3
Circuit breaker
In order to safely disconnect the inverter from the line supply, connect a main switch or a
circuit breaker on the line side of the inverter.
The main switch or the circuit breaker must be capable of carrying at least 1.2 times the
inverter rated current.
The switching capacity of the main switch or the circuit breaker must equal the short-circuit
current of the line supply system.
