VLT
®
8000 AQUA
All about VLT 8000
AQUA
■ Peak voltage on motor
When a transistor in the inverter is opened,
the voltage across the motor increases by a
dU/dt ratio that depends on:
- the motor cable (type, cross-section, length
screened or unscreened)
- inductance
The natural induction causes an overshot U
PEAK
in the
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
PEAK
affect the service
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),therisetimeandpeakvoltagearelower.
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
PEAK
are measured on the motor terminals
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
PEAK
= DC link voltage x 1.9
(DC link voltage = Mains voltage x 1.35).
3.
Data are measured according to IEC 60034-17.
Cable leng
ths are in metres/feet.
VLT 8006-8011 / 380-480 V
Cable
length
Mains
volt-
age Rise time
Peak
voltage dU/dt
50m/164ft 500 V 0.5 µsec. 1230 V 1968 V/µsec.
150m/492ft 500 V 1 µsec. 1270 V 1270 V/µsec.
50m/164ft 380 V 0.6 µsec. 1000 V 1333 V/µsec.
150m/492ft 380 V 1.33
µsec.
1000 V 602 V/µsec.
VLT 8016-8122 / 380-480 V
Cable
length
Mains
volt-
age Rise time
Peak
voltage dU/dt
32m/105ft 380 V 0.27 µsec. 950 V 2794 V/µsec.
70m/230ft 380 V 0.60 µsec. 950 V 1267 V/µsec.
132m/433ft 380 V 1.11 µsec. 950 V 685 V/µsec.
VLT 8152-8352 / 380-480 V
Cable
length
Mains
volt-
age Rise time
Peak
voltage dU/dt
70m/230ft 400 V 0.34
µsec.
1040 V 2447 V/µsec.
VLT 8452-8652 / 380-480 V
Cable
length
Mains
volt-
age Rise time
Peak
voltage dU/dt
29m/95ft 500 V 0.71
µsec.
1165 V 1389 V/µsec.
29m/95ft 400 V 0.61
µsec.
942 V 1233 V/µsec.
VLT 8002-8011 / 525-600 V
Cable
length
Mains
volt-
age Rise time
Peak
voltage dU/dt
35m/115ft 600 V 0.36 µsec. 1360 V 3022 V/µsec.
VLT 8016-8072 / 525-600 V
Cable
length
Mains
volt-
age Rise time
Peak
voltage dU/dt
35m/115ft 575 V 0.38 µsec. 1430 V 3011 V/µsec.
VLT 8052-8402 / 525-690 V
Cable
length
Mains
voltage Rise time
Peak
voltage dU/dt
25m/82ft 690 V 0.59 µsec. 1425 1983 V/µsec.
25m/82ft 575 V 0.66 µsec. 1159 1428 V/µsec.
25m/82ft 690 V
1)
1.72 µsec. 1329 640 V/µsec.
VLT 8502-8652 / 525-690 V
Cable
length
Mains
voltage Rise time
Peak
voltage dU/dt
25m/82ft 690 V 0.57 µsec. 1540 2230 V/µsec.
25m/82ft 575 V 0.25 µsec. 2510 V/µsec.
25m/82ft 690 V
1)
1.13 µsec. 1629 1149 V/µsec.
1) With Dan
foss dU/dt filter.
MG.83.A2.02 - VLT is a registered Danfoss trademark
185
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