Emerson unidrive sp User Manual

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SM-Uni Enc Pl
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266 Unidrive SP Advanced User Guide
www.controltechniques.com Issue Number: 10
The feedback reference scaling is applied as follows:
The position feedback can be used as a reference for any unprotected parameter and is the output from the speed filter (Pr x.19). This value is also
displayed in Pr x.03 after further filtering to aid readability.
The filtered reference is converted to percentage of the maximum position feedback reference (Pr x.20) and displayed via the feedback reference (Pr
x.21). This value is to the nearest tenth of a percent and is limited to ± 100.0%. The limited percentage value is then scaled by the feedback reference
scaling (Pr x.22). This scaled value is also to the nearest tenth of a percent and is also limited to ± 100.0%. The value written to the destination
parameter is converted to a percentage of the full-scale value of the destination (Pr x.23) to the nearest tenth of a percent.
The destination is updated every 4ms.
If the destination for the feedback is the hard speed reference (Pr 3.22), a shortcut facility is provided in the drive. In order to invoke this facility, the
maximum feedback reference (Pr x.20) must be set to the maximum currently used for the hard speed reference and the scaling parameter (Pr x.22)
must be set to 1.0000. The destination is updated every 250μs and a value in rpm is written to Pr 3.22 every 4ms for indication only.
If the destination is default or invalid (non-existent or protected) Pr x.21 displays the motor thermistor resistance in 0.1% of 10kΩ units. This operates
even if Pr x.12 (thermistor enable) is not enabled allowing the user to design their own characteristic without trips using the threshold detector.
Example
Speed is 200rpm Pr x.20 is 400rpm so Pr x.21 shows 50%. Pr x.22 is 0.500 so the final percentage value is 25%. The destination is a 16 bit bipolar
parameter which therefore will have 25% * (2^15) = 8192 written to it.
Effect of encoder resolution
A 1024 line encoder as the input produces 4096 counts per revolution. The resolution is one count per 250μs. As one count is 1/4096th of a
revolution, the speed resolution is actually 58.8rpm.
A 4096 line encoder as the input produces 16384 counts per revolution. As one count is 1/16384th of a revolution, the speed resolution is actually
14.6rpm.
To compensate for the resolution of one count per 250μs the speed filter can be used. For example a filter of 4ms divides the resolution by 16, but
could affect the performance of any control loop.
Effect of percentage resolution
Destinations other than the hard speed reference (Pr 3.22) will be rounded to the nearest tenth of a percent. This would give a minimum resolution of
1 rpm if the destination maximum were 1000.0rpm for example.
The simulated encoder output (incremental), Ab, Ab.L, Fd, Fd.L can be scaled using the above parameter.
x.22 Feedback reference scaling
RW Uni US
Ú
0.000 to 4.000
Ö
1.000
Update rate: Background read
3000rpm Motor
Parameter Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Pr x.20 Max f/b ref 3000.0 1500.0 6000.0 3000.0 1500.0 6000.0
Pr x.21 F/b ref 100.0 100.0 50.0 100.0 100.0 50.0
Pr x.22 F/b ref scaling 1.000 1.000 1.000 0.500 0.500 0.500
Pr x.23 Destination Pr 1.21 Pr 1.21 Pr 1.21 Pr 1.21 Pr 1.21 Pr 1.21
Pr 1.21 Preset speed 3000.0 3000.0 1500.0 1500.0 1500.0 750.0
x.23 Feedback reference destination
RW Uni DE US
Ú
00.00 to 21.51
Ö
00.00
Update rate: Read on reset
x.24 Encoder simulation source
RW Uni PT US
Ú
00.00 to 21.51
Ö
00.00
Update rate: Read on reset
x.25 Encoder simulation ratio numerator
RW Uni US
Ú
0.0000 to 3.0000
Ö
0.2500
Update rate: Background read
NOTE

Emerson unidrive sp Specifications

General

Brand	Emerson
Model	unidrive sp
Category	Controller
Language	English