Danfoss VLT AutomationDrive FC 300 Design Guide

4.6 dU/dt Conditions
NOTICE!
To avoid the premature ageing of motors that are not designed to be used with adjustable frequency 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 adjustable frequency 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 non-shielded)
•
inductance
The natural induction causes an overshoot U
PEAK
in the 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
PEAK
affect the service life of the motor. In particular,
motors without phase coil insulation are affected if the peak voltage is too high. Motor cable length affects the rise time
and peak voltage. For example, if the motor cable is short (a few yards), the rise time and peak voltage are lower. If the
motor cable is long (330 ft. [100 m]), the rise time and peak voltage are higher.
Peak voltage on the motor terminals is caused by the switching of the IGBTs. The adjustable frequency drive complies with
the demands of IEC 60034-25 regarding motors designed to be controlled by adjustable frequency drives. The adjustable
frequency drive also complies with IEC 60034-17 regarding Norm motors controlled by adjustable frequency drives.
High Power Range
The power sizes in Table 4.16 and Table 4.17 at the appropriate AC line voltages comply with the requirements of IEC
60034-17 regarding normal motors controlled by adjustable frequency drives, IEC 60034-25 regarding motors designed to
be controlled by adjustable frequency drives, and NEMA MG 1-1998 Part 31.4.4.2 for inverter fed motors. The power sizes
below do not comply with NEMA MG 1-1998 Part 30.2.2.8 for general purpose motors.
Power size Cable length
[m]
AC line voltage
[V]
Rise time
[µs]
Peak voltage
[V]
dU/dt
[V/µs]
125–350 hp [90–250 kW]/
380–500 V
30 400 0.26 1180 2109`
Table 4.16 dU/dt, D-frame, 380–500 V
Power size Cable length
[m]
AC line voltage
[V]
Rise time
[µs]
Peak voltage
[V]
dU/dt
[V/µs]
425–1075 hp
[315–800 kW]/380–500 V
30 500 0.71 1165 1389
30
500
1)
0.80 906 904
30 400 0.61 942 1233
30
400
1)
0.82 760 743
Table 4.17 dU/dt E-frame, 380–500 V
1)
With Danfoss dU/dt filter
Selection Design Guide
MG34S222 Danfoss A/S © Rev. 2014-02-10 All rights reserved. 85
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Danfoss VLT AutomationDrive FC 300 Specifications

General

Brand	Danfoss
Model	VLT AutomationDrive FC 300
Category	DC Drives
Language	English