30
VLT
®
3500 HVAC
MG.35.B1.02 – VLT is a registered Danfoss trademark
■
Example 7:
In a pump system, a constant pressure of 5 bar is to
be maintained. The integrated PID regulator in VLT
3500 HVAC is used. Normal regulation is desired, in
which the speed is reduced when the pressure increa-
ses and vice versa, i.e. that the speed goes up when
the pressure drops.
The transmitter used is a 4-20 mA, 0-10 bar type.
Since a pressure of 5 bar is required, this corre-
sponds to 50% of the working range of the transmit-
ter, which in turn corresponds to the setpoint pro-
grammed as internal setpoint in VLT 3500 HVAC.
(Digital reference = 50%). The min. speed must be 10
Hz and the max. speed 50 Hz.
NB!:
NB!:
NB!:
NB!:
NB!:
Screen for control cables must be connected
as described in the chapter on EMC-correct
installation.
All settings are based on factory settings; however,
motor data settings (parameters 104, 105 and 107)
(or the Quick Set-up menu items 1, 2 and 3) are to be
adjusted to the motor connected.
1 = Start/Stop
2 = Feedback pressure transmitter 4-20 mA, 0-10 bar
The following must be programmed:
Function
Parameter no.
Parameter value
Data value no.
Activation of
PID-regulator
101
CLOSED LOOP
[2]
Internal setpoint
205
50%
Feedback type
114
CURRENT
[1]
Current signal
413
4-20 mA
[2]
Min. speed
201
10 Hz
Max. speed
202
50 Hz
Regulator range
120
Application-
dependent
Proportional gain
121
Application-
dependent
Integration time
122
Application-
dependent
Ref. independent of
411
Prop w/min
[1]
minimum speed
2.7 Installation examples
