Danfoss VLT Midi Drive FC 280 Programming Manual page 16

Control
The settings in parameter 9-16 PCD Read Configuration
define the content of PCD 3 to PCD 10.
4.2.3 Reference Handling
The reference handling is an advanced mechanism that
sums up references from different sources, as shown in
Illustration 4.2.
4 4
For more information on reference handling, refer to the
design guide.
Illustration 4.2 Reference
The reference, or speed setpoint, is sent via PROFIBUS and
is always transmitted to the frequency converter in
percentage format as integers shown in hexadecimal (0–
4000 hex).
The reference (MRV) and feedback (MAV) are always scaled
equally. The setting of parameter 3-00 Reference Range
determines the scaling of the reference and feedback
(MAV), see Illustration 4.3.
Illustration 4.3 Reference (MRV) and Feedback (MAV), Scaled
NOTICE
When parameter 3-00 Reference Range is set to [0] Min -
Max, a negative reference is handled as 0%.
14
PROFIBUS DP
The actual output of the frequency converter is limited by
the speed limit parameters Motor Low/High Speed Limit
[RPM/Hz] in parameter 4-12 Motor Speed Low Limit [Hz] and
parameter 4-14 Motor Speed High Limit [Hz].
The final speed limit is set in parameter 4-19 Max Output
Frequency.
Table 4.3 lists the reference (MRV) and the feedback (MAV)
formats.
Table 4.3 Reference/Feedback (MRV/MAV) Format
NOTICE
Negative numbers are formed as complement of 2.
NOTICE
The data type for MRV and MAV is an N2 16-bit
standardized value, expressing a range from -200% to
+200% (8000 to 7FFF).
Example
The following settings determine the speed, as shown in
Table 4.4:
•
•
•
•
Table 4.4 Actual Speed for MRV/MAV
Danfoss A/S © 05/2016 All rights reserved.
MRV/MAV Integer in hex
100% 4000
75% 3000
50% 2000
25% 1000
0% 0
-25% F000
-50% E000
-75% D000
-100% C000
Parameter 1-00 Configuration Mode set to [0]
Speed open loop.
Parameter 3-00 Reference Range set to [0] Min-Max.
Parameter 3-02 Minimum Reference set to 0 Hz.
Parameter 3-03 Maximum Reference set to 50 Hz.
MRV/MAV
0% 0 hex
25% 1000 hex
50% 2000 hex
75% 3000 hex
100% 4000 hex
Integer in decimal
16384
12288
8192
4096
0
-4096
-8192
-12288
-16384
Actual speed [Hz]
0
12.5
25
37.5
50
MG07F102