Planning the electrical installation
64
Note 9: Sine filters
Sine filters protect the motor insulation system. Therefore, a du/dt filter can be replaced with a sine
filter. The peak phase-to-phase voltage with a sine filter is approximately 1.5 × U
N
.
Permanent magnet synchronous motor
Only one permanent magnet motor can be connected to the inverter output.
It is recommended to install a safety switch between a permanent magnet
synchronous motor and the motor cable. The switch is needed to isolate the motor
during any maintenance work on the drive.
Thermal overload and short-circuit protection
The drive protects itself and the input and motor cables against thermal overload
when the cables are dimensioned according to the nominal current of the drive. No
additional thermal protection devices are needed.
WARNING! If the drive is connected to multiple motors, a separate thermal overload
switch or a circuit breaker must be used for protecting each cable and motor. These
devices may require a separate fuse to cut off the short-circuit current.
The drive protects the motor cable and the motor in a short-circuit situation when the
motor cable is dimensioned according to the nominal current of the drive.
Û
LL
/U
N
Without du/dt Filter
Cable length (m)
du/dt
U
N
-------------(1/µs)
1.0
2.0
5.0
4.0
3.0
1.5
2.5
3.5
4.5
100 200 300
100 200 300
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Cable length (m)
With du/dt Filter
du/dt
U
N
-------------(1/µs)
Û
LL
/U
N
5.5
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