Reference Handling - Danfoss VLT AutomationDrive FC 300 Design Manual

FC 300 Design Guide
The Remote reference is calculated once every scan interval and initially consists of two parts:
X (the external reference) : A sum of up to four externally selected references, comprising any
1.
combination (determined by the setting of par. 3-15, 3-16 and 3-17) of a fixed preset reference (par.
3-10), variable analog references, variable digital pulse references, and various serial bus references
in whatever unit the adjustable frequency drive is controlled ([Hz], [RPM], [Nm] etc.).
Y- (the relative reference): A sum of one fixed preset reference (par. 3-14) and
2.
one variable analog reference (par. 3-18) in [%].
The two parts are combined in the following calculation: Auto reference = X + X * Y / 100%. The
Catch up / slow-down function and the Freeze reference function can both be activated by digital
inputs on the adjustable frequency drive. They are described in par. group 5-1*.
The scaling of analog references is described in par. groups 6-1* and 6-2*, and the scaling
of digital pulse references is described in par. group 5-5*.
Reference limits and ranges are set in par. group 3-0*.
References and feedback can be scaled in physical units (i.e. RPM, Hz, °C) or simply in % relating
to the values of par. 3-02 Minimum Reference and par. 3-03 Maximum Reference.
In this case, all analog and pulse inputs are scaled according to the following rules:
When par. 3-00 Reference Range is [0] Min - Max, 0% reference equals 0 [unit], where unit
•
can be any unit e.g. rpm, m/s, bar etc., 100% reference equals the Max (abs (par. 3-03
Maximum Reference), abs (par. 3-02 Minimum Reference)).
When par. 3-00 Reference Range: [1] -Max - +Max, 0% reference equals 0 [unit], -100%
•
reference equals -Max Reference, 100% reference equals Max Reference.
Bus references are scaled according to the following rules:
When par. 3-00 Reference Range is [0] Min - Max. To obtain max resolution on the bus reference, the
•
scaling on the bus is: 0% reference equals Min Reference, 100% reference equals Max reference.
When par. 3-00 Reference Range: [1] -Max - +Max, -100% reference equals -Max
•
Reference, 100% reference equals Max Reference.
Par. 3-00 Reference Range, 3-02 Minimum Reference and 3-03 Maximum Reference together define the
allowed range of the sum of all references. The sum of all references is clamped when necessary. The relation
between the resulting reference (after clamping) and the sum of all references is shown below.
Introduction to FC 300
MG.33.B3.22 - VLT is a registered Danfoss trademark
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