Danfoss VLT HVAC Drive FC 100 Series Design Manual page 31

®
VLT HVAC Drive Design Guide
Parameter
Feedback 1 Source
Reference/Feedback Unit
PID Normal/Inverse Control
PID Proportional Gain
PID Integral Time
This table summarizes the parameters that are needed to set up the frequency converter's Closed Loop Controller when a single feedback signal with no
conversion is compared to a single setpoint. This is the most common type of Closed Loop Controller.
2.8.2. Closed Loop Control Relevant Parameters
The frequency converter's Closed Loop Controller is capable of handling more complex applications, such as situations where a conversion function is
applied to the feedback signal or situations where multiple feedback signals and/or setpoint references are used. The below table summarizes the
additional parameters than may be useful in such applications.
Parameter
Feedback 2 Source
Feedback 3 Source
Feedback 1 Conversion
Feedback 2 Conversion
Feedback 3 Conversion
Feedback 1 Source Unit
Feedback 2 Source Unit
Feedback 3 Source Unit
Feedback Function
Setpoint 1
Setpoint 2
Setpoint 3
Refrigerant
Description of function
par. 20-00 Select the source for Feedback 1. This is most commonly an analog input, but other sources are
also available. Use the scaling of this input to provide the appropriate values for this signal. By
default, Analog Input 54 is the default source for Feedback 1.
par 20-12 Select the unit for the setpoint referenceand feedback for the frequency converter's Closed Loop
Controller. Note: Because a conversion can be applied to the feedback signal before it is used
by the Closed Loop Controller, the Reference/Feedback Unit (par. 20-12) may not be the same
as the Feedback Source Unit (par. 20-02, 20-05 and 20-08).
Normal
par. 20-81 Select [0] if the motor's speed should decrease when the feedback is greater than the
setpoint reference. Select
is greater than the setpoint reference.
par. 20-93 This parameter adjusts the output of the frequency converter's closed loop controlled based on
the error between the feedback and the setpoint reference. Quick controller response is obtained
when this value is large. However, if too large of a value is used, the frequency converter's output
frequency may become unstable.
par. 20-94 The integrator adds over time (integrates) the error between the feedback and the setpoint
reference. This is required to ensure that the error approaches zero. Quick controller response
is obtained when this value is small. However, if too small of a value is used, the frequency
converter's output frequency may become unstable. A setting of 10000 s disables the integrator.
Description of function
par. 20-03 Select the source, if any, for Feedback 2 or 3. This is most commonly a frequency con-
par. 20-06 verter analog input, but other sources are also available. Par. 20-20 determines how
multiple feedback signals will be processed by the frequency converter's Closed Loop
Controller. By default, these are set to
par. 20-01 These are used to convert the feedback signal from one type to another, for example
par. 20-04 from pressure to flow or from pressure to temperature (for compressor applications).
Pressure to temperature
par. 20-07 If
Group 20-3*, Feedback Adv. Conv. By default, these are set to
par. 20-02 Select the unit for a feedback source, prior to any conversions. This is used for display
par. 20-05 purposes only. This parameter is only available when using
par. 20-08 feedback conversion.
par. 20-20 When multiple feedbacks or setpoints are used, this determines how they will be pro-
cessed by the frequency converter's Closed Loop Controller.
par. 20-21 These setpoints can be used to provide a setpoint reference to the frequency converter's
par. 20-22 Closed Loop Controller. Par. 20-20 determines how multiple setpoint references will be
par. 20-23 processed. Any other references that are activated in par. group 3-1* will add to these
values.
par. 20-30 If any Feedback Conversion (par. 20-01, 20-04 or 20-07) is set to
ature [2], the refrigerant type must be selected here. If the refrigerant used is not listed
here, select
20-31, 20-32 and 20-33.
MG.11.B7.02 - VLT ® is a registered Danfoss trademark
2. Introduction to VLT HVAC Drive
Inverse
[1] if the motor's speed should increase when the feedback
No function
[2] is selected, the refrigerant must be specified in par.
User defined
[7] and specify the characteristics of the refrigerant in par.
[0].
Linear
[0].
Pressure to Temperature
Pressure to Temper-
2
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