MG.20.B6.02 – VLT is a registered Danfoss trademark
VLT
®
2000 Series
94
du/dt measurements
When a transistor in the inverter is activated, the volt-
age applied to the motor will rise by a flank. The du/dt
ratio on the flank is determined by
− Motor cable (type, cross section, length)
− Inductance
The self-inductance will cause an overshoot U
PEAK
in
the motor voltage before it stabilises at a level
determined by the voltage in the intermediate circuit.
Both the du/dt ratio and the U
PEAK
peak voltage affect
the lifetime of the motor. Too high values will primarily
affect motors without phase coil insulation.
With short (a few metres) motor cable, the du/dt ratio
will be high but the peak voltage low.
With long (100 metres) motor cable, the du/dt ratio
will decrease and the U
PEAK
peak voltage will increase.
If you use very small motors without phase coil
insulation we recommend to mount an LC filter in se-
ries with the motor.
Typical values for the du/dt ratio and the U
PEAK
peak
voltage measured between two phases (5 m and
275 m screened motor cable)
are listed below:
U
PEAK
[V]
Cable length 5 m 275 m
VLT 2030 464 V 744 V
VLT 2030 with motor coil IP 20 516 V 744 V
VLT 2030 with motor coil IP 00 440 V 628 V
du/dt [V/
µµ
µµ
µs]
Cable length 5 m 275 m
VLT 2030 3727 V/µs 253 V/µs
VLT 2030 with motor coil IP 20 690 V/µs 157 V/µs
VLT 2030 with motor coil IP 00 359 V/µs 93 V/µs
Derating for high ambient temperature
The ambient temperature is the maximum temperature
allowed. The average over 24 hours must be at least
5 °C lower according to VDE 0160 5.2.1.1.
The derating for VLT 2010-2060
40 °C: 100% output, 45 °C: 84% output, 50 °C: 67% output, 55 °C: 50% output
If the VLT frequency converter is operated at tempera-
tures above 40 °C, then a derating of the output
current is necessary.
At higher temperatures, derating will not be possible
due to the load-independent temperature on the
SMPS transistors.
Special conditions
Note: The above measurements are for VLT 2030, 1/3 x 208-240 V installed on single-phased mains
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