Peak Voltage On Motor; Switching On The Input - Danfoss VLT 6000 series Operating Instructions Manual

Peak voltage on motor

When a transistor in the inverter is opened,
the voltage across the motor increases by a
dV/dt ratio that depends 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
primarily 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
insulation, it is recommended to fit a LC filter
after the frequency converter.
Typical values for the rise time and peak voltage
U are measured on the motor terminals
PEAK
between 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).
3.
Data are measured according to IEC 60034-17.
VLT 6002-6011 / 380-460 V
Mains
Cable volt-
length age Rise time
0.3 µsec.
50 metres 380 V
0.4 µsec.
50 metres 500 V
1.2 µsec.
150 metres 380 V
1.3 µsec.
150 metres 500 V
VLT 6016-6122 / 380-460 V
Mains
Cable volt-
length age Rise time
0.27 µsec.
32 metres 380 V
0.60 µsec.
70 metres 380 V
1.11 µsec.
132 metres 380 V
150
in the
PEAK
affect the service
PEAK
Peak
voltage dU/dt
850 V 2000 V/µsec.
950 V 2600 V/µsec.
1000 V 667 V/µsec.
1300 V 800 V/µsec.
Peak
voltage dU/dt
950 V 2794 V/µsec.
950 V 1267 V/µsec.
950 V 685 V/µsec.
®
VLT 6000 HVAC Series
VLT 6152-6352 / 380-460 V
Mains
Cable volt-
length age Rise time
0.34 µsec.
70 metres 400 V
VLT 6402-6602 / 380-460 V
Mains
Cable volt-
length age Rise time
0.71 µsec.
29 metres 500 V
0.61 µsec.
29 metres 400 V
VLT 6002-6011 / 525-600 V
Mains
Cable volt-
length age Rise time
0.36 µsec.
35 metres 600 V
VLT 6016-6072 / 525-600 V
Mains
Cable volt-
length age Rise time
0.38 µsec.
35 metres 575 V
VLT 6102-6402 / 525-600 V
Cable Mains
length voltage Rise time
0.45 µsec.
25 metres 575 V
VLT 6502-6652 / 525-600 V
Cable Mains
length voltage Rise time
0.25 µsec.
25 metres 575 V

Switching on the input

Switching on the input depends on the mains
voltage in question.
The table states the waiting time between cut-ins.
Mains voltage 380 V
Waiting time 48 s
MG.61.A5.02 - VLT is a registered Danfoss trademark
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
voltage dU/dt
1159 1428 V/µsec.
Peak
voltage dU/dt
1159 2510 V/µsec.
415 V 460 V
65 s 89 s