Planning the electrical installation
46
Note 7: Calculating the rise time and the peak line-to-line voltage
The peak line-to-line voltage at the motor terminals generated by the drive as well as the voltage rise
time depend on the cable length. The requirements for the motor insulation system given in the table
are “worst case” requirements covering installations with 30 metre and longer cables. The rise time can
be calculated as follows: t = 0.8 · Û
LL
/(du/dt). Read Û
LL
and du/dt from the diagrams below. M
ultiply
the values of the graph by the supply voltage
(U
N
)
.With resistor braking, the Û
LL
and du/dt values are
approximately 20 % higher.
Note 8: Sine filters protect the motor insulation system. Therefore, du/dt filter can be replaced with
a sine filter. The peak phase-to-phase voltage with the sine filter is approximately 1.5 × U
N
.
Note 9: Common mode filter is available as a separate kit (one box including three rings for one cable).
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 the permanent magnet
synchronous motor and the drive output. The switch is needed to isolate the motor
during any maintenance work on the drive.
Supply connection
Disconnecting device (means)
Install a hand-operated input disconnecting device (disconnecting means) between
the AC power source and the drive. The disconnecting device must be of a type that
can be locked to the open position for installation and maintenance work.
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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