Peak Voltage On Motor - Danfoss VLT 5000 Series Design Manual

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
screened or unscreened)
inductance
-
The natural induction causes an overshot U
motor voltage before it stabilises 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 (a few
metres), the rise time and peak voltage are lower.
If the motor cable is long (100 m), the rise time and
peak voltage will increase.
If very small motors are used without phase coil insu-
lation, it is recommended to fit a sine-wave filter after
the frequency converter.
Typical values for the rise time and peak voltage
are measured on the motor terminals between
U
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 = Mains voltage x 1.35).
/
0.5 ×
3.
dU dt
=
Risetime
112
in the
PEAK
affect the service
PEAK
U
PEAK
®
VLT 5000 Design Guide
Data are measured according to IEC 60034-17.
VLT 5001-5011 / 380-500 V
Cable Mains
length voltage Rise time
0.5 µsec.
50 metres 500 V
1 µsec.
150 metres 500 V
0.6 µsec.
50 metres 380 V
1.33 µsec.
150 metres 380 V
VLT 5016-5102 / 380-500 V
Cable Mains
length voltage Rise time
0.27 µsec.
32 metres 380 V
0.60 µsec.
70 metres 380 V
1.11 µsec.
132 metres 380 V
VLT 5122-5302 / 380-500 V
Cable Mains
length voltage Rise time
0.34 µsec.
70 metres 400 V
VLT 5352-5552 / 380-500 V
Cable Mains
length voltage Rise time
0.71 µsec.
29 metres 500 V
0.61 µsec.
29 metres 400 V
VLT 5001-5011 / 525-600 V
Cable Mains
length voltage Rise time
0.36 µsec.
35 metres 600 V
VLT 5016-5062 / 525-600 V
Cable Mains
length voltage Rise time
0.38 µsec.
35 metres 575 V
VLT 5042-5352 / 525-690 V
Cable Mains
length voltage
25 metres 690 V
25 metres 575 V
25 metres 1)
690 V
1) With Danfoss dU/dt filter.
VLT 5402-5602 / 525-690 V
Cable Mains
length voltage Rise time
0.57 µsec.
25 metres 690 V
0.25 µsec.
25 metres 575 V
1.13 µsec.
1)
25 metres
690 V
1) With Danfoss dU/dt filter.
®
MG.52.B2.02 - VLT is a registered Danfoss trademark
Peak
voltage dU/dt
1230 V
1968 V/µsec.
1270 V
1270 V/µsec.
1000 V
1333 V/µsec.
1000 V 602 V/µsec.
Peak
voltage dU/dt
950 V
2794 V/µsec.
950 V 1267 V/µsec.
950 V 685 V/µsec.
Peak
voltage dU/dt
1040 V 2447 V/µsec.
Peak
voltage dU/dt
1165 V 1389 V/µsec.
942 V
1233 V/µsec.
Peak
voltage dU/dt
1360 V 3022 V/µsec.
Peak
voltage dU/dt
1430 V 3011 V/µsec.
Peak
Rise time voltage dU/dt
0.59 µsec. 1425
1983 V/µsec.
0.66 µsec. 1159
1428 V/µsec.
1.72 µsec. 1329
640 V/µsec.
Peak
voltage dU/dt
1540
2.230 V/µsec.
2.510 V/µsec.
1629 1.150 V/µsec.