Danfoss VLT 5000 Series Instruction Manual page 213

Peak voltage on motor
When a transistor in the inverter is opened, the voltage
across the motor increases by a dU/dt ratio that de-
pends on:
the motor cable (type, cross-section, length,
-
shielded or unshielded)
inductance
-
The natural induction causes an overshot U
motor voltage before it stabilizes itself at a level which
depends on the voltage in the intermediate circuit. The
rise time and the peak voltage U
life of the motor. If the peak voltage is too high, motors
without phase coil insulation are the ones that will pri-
marily be affected. If the motor cable is short (by a few
yards), the rise time and peak voltage are lower.
If the motor cable is long (328 ft [100 m]), the rise time
and peak voltage will increase.
If very small motors without phase coil insulation are
used, it is recommended that an LC filter be fitted after
the adjustable frequency drive.
Typical values for the rise time and peak voltage
U are measured on the motor terminals between
PEAK
two phases.
To obtain approximate values for cable lengths and
voltages not mentioned below, use the following rules
of thumb:
1. Rise time increases/decreases proportionally with
cable length.
2. U = DC link voltage x 1.9
PEAK
(DC link voltage = Line voltage x 1.35).
U
3. 0.5 ×
/
dU dt
=
Rise time
Data are measured according to IEC 60034-17.
210
in the
PEAK
affect the service
PEAK
PEAK
®
VLT 5000 Series
VLT 5001-5011 / 380-500 V
Cable AC line
length voltage Rise time
164 ft [50 m] 500 V 0.5 sec
492 ft [150 m] 500 V 1 sec
164 ft [50 m] 380 V 0.6 sec
492 ft [150 m] 380 V 1.33 sec
VLT 5016-5102 / 380-500 V
Cable AC line
length voltage Rise time
105 ft [32 m] 380 V 0.27 sec
230 ft [70 m] 380 V 0.60 sec
433 ft [132 m] 380 V 1.11 sec
VLT 5122-5302 / 380-500 V
Cable AC line
length voltage Rise time
230 ft [70 m] 400 V 0.34 sec
VLT 5352-5552 / 380-500 V
Cable AC line
length voltage Rise time
95 ft [29 m] 500 V 0.71 sec
95 ft [29 m] 400 V 0.61 sec
VLT 5001-5011 / 525-600 V
AC line
Cable volt-
length age Rise time
115 ft [35 600 V 0.36 sec
m]
VLT 5016-5062 / 525-600 V
Cable AC line
length voltage Rise time
115 ft [35 m] 575 V 0.38 sec
VLT 5042-5352 / 525-690 V
Cable AC line
length voltage
82 ft [25 m] 690 V
82 ft [25 m] 575 V
1)
82 ft [25 m] 690 V
1) With Danfoss dU/dt filter.
VLT 5402-5602 / 525-690 V
Cable AC line
length voltage Rise time
82 ft [25 m] 690 V 0.57 sec
82 ft [25 m] 575 V 0.25 sec
82 ft [25 m] 1) 1.13 sec
690 V
1) With Danfoss dU/dt filter.
MG.51.C5.22 - VLT is a registered Danfoss trademark.
Peak
voltage dU/dt
1230 V 1968 V/sec
1270 V 1270 V/sec
1000 V 1333 V/sec
1000 V 602 V/sec
Peak
voltage dU/dt
950 V 2794 V/sec
950 V 1267 V/sec
950 V 685 V/sec
Peak
voltage dU/dt
1040 V 2447 V/sec
Peak
voltage dU/dt
1165 V 1389 V/sec
942 V 1233 V/sec
Peak
voltage dU/dt
1360 V 3022 V/sec
Peak
voltage dU/dt
1430 V 3011 V/sec
Peak
Rise time voltage dU/dt
0.59 sec 1425 1983 V/sec
0.66 sec 1159 1428 V/sec
1.72 sec 1329 640 V/sec
Peak
voltage dU/dt
1540 2.230 V/sec
2.510 V/sec
1629 1.150 V/sec