Danfoss VLT AQUA Drive Design Manual page 24

2. Introduction to VLT AQUA Drive
Parameter
Feedback 2 Source
Feedback 3 Source
Feedback 1 Conversion
Feedback 2 Conversion
2
Feedback 3 Conversion
Reference Feedback
Feedback Function
Setpoint 1
Setpoint 2
Setpoint 3
Setpoint Adjustment Factor
PID Start Speed [RPM]
PID Start Speed [Hz]
On Reference Bandwidth
PID Anti Windup
PID Differentiation Time
PID Diff. Gain Limit
Flow Compensation
Square-linear Curve Approximation
Work Point Calculation
Speed at No-Flow [RPM]
Speed at No-Flow [Hz]
Speed at Design Point [RPM]
Speed at Design Point [Hz]
Pressure at No-Flow Speed
Pressure at Rated Speed
Flow at Design Point
Flow at Rated Speed
Lowpass Filter Time :
Analog Input 53
Analog Input 54
Digital (pulse) input 29
Digital (pulse) input 33
24
Par. No. Description of function
20-03 Select the source, if any, for Feedback 2 or 3. This is most commonly a
20-06 drive analog input, but other sources are also available. Par. 20-20 de-
termines how multiple feedback signals will be processed by the drive's
Closed Loop Controller. By default, these are set to
20-01 These are used to convert the feedback signal from one type to another,
20-04 for example from pressure to flow.
Flow Pressure
=
20-07
20-12 For setting the unit used for setpoint reference and feedback.
20-20 When multiple feedbacks or setpoints are used, this determines how they
will be processed by the drive's Closed Loop Controller.
20-21 These setpoints can be used to provide a setpoint reference to the drive's
20-22 Closed Loop Controller. Par. 20-20 determines how multiple setpoint ref-
20-23 erences will be processed. Any other references that are activated in par.
20-29 group 3-1* will add to these values.
Par. 20-29 can be used to reduce the setpoint at low flow benefiting from
a reduced pipe resistance at reduced flow.
20-82 The parameter that is visible will depend on the setting of par. 0-02,
20-83 Motor Speed Unit. In some applications, after a start command it is im-
portant to quickly ramp the motor up to some pre-determined speed
before activating the drive's Closed Loop Controller. This parameter de-
fines that starting speed.
20-84 This determines how close the feedback must be to the setpoint refer-
ence for the drive to indicate that the feedback is equal to the setpoint.
On
20-91 [1] effectively disables the Closed Loop Controller's integral function
when it is not possible to adjust the output frequency of the drive to
correct the error. This allows the controller to respond more quickly once
it can again control the system.
integral function stay active continuously.
20-95 This controls the output of the drive's Closed Loop Controller based on
the rate of change of feedback. While this can provide fast controller
response, such response is seldom needed in Water systems. The default
value for this parameter is Off, or 0.00 s.
20-96 Because the differentiator responds to the rate of change of the feed-
back, a rapid change can cause a large, undesired change in the output
of the controller. This is used to limit the maximum effect of the differ-
entiator. This is not active when par. 20-95 is set to Off.
22-80 It is sometimes the case that it is not possible for a pressure transducer
22-81 to be placed at a remote point in the system and it can only be located
22-82 close to the fan/pump outlet. Flow compensation operates by adjusting
22-83 the setpoint according to the output frequency, which is almost propor-
22-84 tional to flow, thus compensating for higher losses at higher flow rates.
22-85 These parameters are used for setting up flow compensation.
22-86
22-87
22-88
22-89
22-90
6-16 This is used to filter out high frequency noise from the feedback signal.
6-26 The value entered here is the time constant for the low pass filter. The
5-54 cut-off frequency in Hz can be calculated as follows:
5-59
F cut
=
− off
2π T lowpass
Variations in the feedback signal whose frequency is below F
used by the drive's Closed Loop Controller, while variations at a higher
frequency are considered to be noise and will be attenuated. Large values
of Lowpass Filter Time will provide more filtering, but may cause the
controller to not respond to actual variations in the feedback signal.
®
MG.20.N4.02 - VLT is a registered Danfoss trademark
®
VLT AQUA Drive Design Guide
No function
Off
[0] disables this function, making the
1
[0].
will be
cut-off