Danfoss VLT 2800 Series, Operating Instructions Manual

Page: 46 / 103

Description of choice:
Select how long the frequency converter should main-
tain the output current at the current limit I
LIM
before it
disconnects. At OFF parameter 409 Trip delay over-
current, I
LIM
is not working, i.e. disconnection will not
take place.
411 Switching frequency
(Switch freq.)
Value:
3000 - 14000 Hz (VLT 2803 - 2875)
4500 Hz
3000 - 10000 Hz (VLT 2880 - 2882)
4500 Hz
Function:
The set value determines the switching frequency of
the inverter. If the switching frequency is changed, this
may help to minimise possible acoustic noise from the
motor.
NB!
The output frequency of the frequency
converter can never assume a value high-
er than 1/10 of the switching frequency.
Description of choice:
When the motor is running, the switching frequency is
adjusted in parameter 411
Switching frequency until
the frequency has been obtained at which the motor is
as low-noise as possible.
NB!
The switching frequency is reduced auto-
matically as a function of the load. See
Temperature-Dependent Switching Fre-
quency under Special Conditions .
When LC-filter connected is selected in
parameter 412, the minimum switching
frequency is 4.5 kHz.
412 Variable switching frequency
(Var carrier freq.)
Value:
Without LC-filter (WITHOUT LC-FILTER) [2]
LC-filter connected
(LC-filter connected)
[3]
Function:
The parameter must be set to LC-filter connected if an
LC-filter is connected between the frequency convert-
er and the motor.
Description of choice:
The LC-filter connected [3] must be used if an LC-filter
is connected between the frequency converter and the
motor, as otherwise the frequency converter cannot
protect the LC-filter.
NB!
When the LC filter is selected the switch-
ing frequency is changed to 4.5 kHz.
413 Overmodulation function
(OVERMODULATION)
Value:
Off (off) [0]
On (on) [1]
Function:
This parameter allows connection of the overmodula-
tion function for the output voltage.
Description of choice:
Off [0] means that there is no overmodulation of the
output voltage, which means that torque ripple on the
motor shaft is avoided. This can be a good feature, e.g.
on grinding machines.
On [1] means that an output
voltage can be obtained which is greater than the
mains voltage (up to 5 %).
414 Minimum feedback, FB
MIN
(Min. feedback)
Value:
-100,000.000 - par. 415 FB
MAX
0.000
Function:
Parameter 414 Minimum feedback, FB
MIN
and 415
Maximum feedback, FB
MAX
are used to scale the dis-
play text to make it show the feedback signal in a
process unit proportionally to the signal on the input.
Description of choice:
Set the value to be shown on the display as the mini-
mum feedback signal value on the selected feedback
input (parameters 308/314
Analogue inputs ).
VLT
®
2800 Series
= factory setting, () = display text, [] = value for use in communication via serial communication port
MG.27.A2.02 - VLT
®
is a registered Danfoss trademark 45
Programming