55
VLT
®
3500 HVAC
MG.35.B1.02 – VLT is a registered Danfoss trademark
Section 1Section 1Section 1Section 1Section 1
Section 2Section 2Section 2Section 2Section 2
Section 3Section 3Section 3Section 3Section 3
Section 4Section 4Section 4Section 4Section 4
225 Output frequency dependent carrier
frequency (VAR.CARR.FREQ.)
Value, VLT 3502-62 (Version 3.0)
★
OFF (DISABLE)
[0]
ON (ENABLE)
[1]
Value, VLT 3542-62 (230 V) and 3575-3800 (Ver. 3.11)
OFF (DISABLED)
[
0
]
High switching frequency at low speed
(HI.CAR.FREQ.LO)
[
1
]
★
Low switching frequency at low speed
(LO.CAR.FREQ.LO)
[
2
]
Function:
The output frequency dependent switching frequency
means that the switching frequency changes with
changes in the output frequency. However, the
maximum switching frequency is determined by para-
meter 224.
Description of choice, version 3.0:
The output frequency dependent switching frequency
can be activated, i.e. On (ENABLED) or not activated,
i.e. Off (DISABLED).
This function gives a high switching frequency at low
speed. In the range from 0-50% of the nominal output
frequency, the switching frequency = data for par.
224. From 50-100% of the nominal output frequency
the switching frequency is reduced to 4.5 kHz. The
function helps to reduce acoustic motor interference.
When an output frequency dependent switching
frequency is used (ASFM), there is typically no
derating. See chapter on optimally low motor
interference.
Description of choice, version 3.11:
NB!:
NB!:
NB!:
NB!:
NB!:
If the VLT has a LC filter, the output frequency
dependent switching frequency must be set at
OFF (0) and 4.5 kHz must be chosen in
parameter 224.
232 Idle running current (CURR.MIN VALUE)
Value:
0-I
LIM
★
Depends on unit
Function:
This is where the minimum motor current value (idle
running current) is programmed.
As soon as the value drops below the preset value
and the maximum output frequency is reached, a sig-
nal can be activated by means of a relay.
This function can be used e.g. for monitoring whether
the V- belt has broken.
I
LIM
is the current limit programmed in parameter 209.
Description of choice:
The relay is activated (parameter 409) [17] and (para-
meter 410) [17] when the motor current drops below
the set idle running value and the maximum output
frequency is reached.
★
= factory setting. Text in ( ) = display text. Figures in [ ] are used when communicating with the bus.
3.6 Parameter gr
oup 2
VLT 3542-3562 (230 V) and VLT 3575-3800:
It can be chosen that the output frequency dependent
switching frequency is not activated, i.e. Off (DISABLED).
The output dependent switching frequency will result in a
permanent switching frequency if Off is selected.
The option of High switching frequency at low speed is
not available (has no function) on these units.
If Low switching frequency at low speed is selected, the
switching frequency will start at 1.1 kHz at a low output
frequency and current. From 8 Hz the switching
frequency increases to 4.5 kHz. This function imporves
the stability of the motor.
