Du/Dt Conditions - Danfoss VLT AutomationDrive FC 361 Series Design Manual

Electrical Installation Con...

7.12 dU/dt Conditions

NOTICE
To avoid the premature aging of motors that are not
designed to be used with drives, such as those motors
without phase insulation paper or other insulation
reinforcement, Danfoss strongly recommends a dU/dt
filter or a sine-wave filter fitted on the output of the
drive. For further information about dU/dt and sine-wave
filters, see the Output Filters Design Guide.
When a transistor in the inverter bridge switches, the
voltage across the motor increases by a dU/dt ratio
depending on the motor cable (type, cross-section, length
shielded or unshielded) and the inductance.
The natural induction causes an overshoot U
7 7
motor voltage before it stabilizes itself at a level
depending on the voltage in the intermediate circuit. The
rise time and the peak voltage U
of the motor. In particular, motors without phase coil
7.12.1 dU/dt Test Results for Enclosures J8–J9
Power size [kW (hp)]
90–160 (125–250)
200–315 (300–450)
Table 7.12 IEC dU/dt Test Results for J8–J9 with Unshielded Cables and No Output Filter, 380–480 V
Power size [kW (hp)]
90–160 (125–250)
200–315 (300–450)
Table 7.13 IEC dU/dt Test Results for J8–J9 with Shielded Cables and No Output Filter, 380–480 V
50
VLT® AutomationDrive FC 361
in the
PEAK
affect the service life
PEAK
Cable [m (ft)] Mains voltage [V]
30 (98) 500
150 (492) 500
300 (984) 500
30 (98) 500
150 (492) 500
300 (984) 500
Cable [m (ft)] Mains voltage [V]
30 (98) 500
150 (492) 500
300 (984) 500
30 (98) 500
150 (492) 500
300 (984) 500
Danfoss A/S © 03/2019 All rights reserved.
insulation are affected if the peak voltage is too high.
Motor cable length affects the rise time and peak voltage.
If the motor cable is short (a few meters), the rise time and
peak voltage are lower. If the motor cable is long (100 m
(328 ft)), the rise time and peak voltage are higher.
Peak voltage on the motor terminals is caused by the
switching of the IGBTs. The drive complies with the
demands of IEC 60034-25:2007 edition 2.0 regarding
motors designed to be controlled by drives. The drive also
complies with IEC 60034-17:2006 edition 4 regarding Norm
motors controlled by drives.
High-power range
The power sizes in Table 7.12 to Table 7.13 at the
appropriate mains voltages comply with the requirements
of IEC 60034-17:2006 edition 4 regarding normal motors
controlled by drives, IEC 60034-25:2007 edition 2.0
regarding motors designed to be controlled by drives, and
NEMA MG 1-1998 Part 31.4.4.2 for inverter-fed motors. The
power sizes in Table 7.12 to Table 7.13 do not comply with
NEMA MG 1-1998 Part 30.2.2.8 for general purpose motors.
Rise time [µs] Peak voltage [V]
0.71 1180
0.76 1423
0.91 1557
1.10 1116
2.53 1028
1.29 835
Rise time [µs] Peak voltage [V]
– –
0.66 1418
0.96 1530
– –
0.56 1261
0.78 1278
dU/dt [V/µs]
1339
1497
1370
815
321
517
dU/dt [V/µs]
–
1725
1277
–
1820
1295
MG06K102