Parameter structure Keypad and display Parameter x.00
Parameter description
format
Advanced parameter
descriptions
Serial comms
protocol
Performance
20 Mentor MP Advanced User Guide
www.controltechniques.com Issue Number: 4
4.3 Update rates
Update rates are given for every parameter in the header table as shown below:
Some parameters have an increased update in special circumstances.
4.3.1 Speed reference update rate
The normal update rate for the speed references (via menu 1) is 4 ms,
however it is possible to reduce the sample time to 250 μs by selecting
the reference from particular sources. The fast update rate is only
possible provided the conditions given below are met. (Note: high speed
updating is not provided for speed references).
Analog input references (not including I/O expansion Solutions
Module)
1. The reference must be derived via Pr 1.36 or Pr 1.37
2. The analog inputs must be in voltage mode with zero offset
3. Bipolar mode must be used or unipolar mode with the minimum
speed (Pr 1.07 {SE01, 0.22}) set to zero
4. No skip bands are enabled, i.e. Pr 1.29, Pr 1.31 and Pr 1.33 must be
zero.
5. The jog and velocity feed-forward references must not be enabled.
Applications and fieldbus Solutions Modules
Pr 91.02 must be used to define the speed reference (this parameter is
only visible from the Solutions Modules). Any value written to Pr 91.02
should be automatically mapped into preset Pr 1.21 by the Solutions
Module.
When fast updating is used the scaling is performed by a simple
multiplication. The scale factor used for the multiplication cannot exactly
duplicate the scaling for the two stage conversion (i.e. conversion in
menu 7 to a percentage of full scale, and conversion to 0.1 rpm units)
used when high speed updating is not in operation. Therefore the
absolute scaling of the analog inputs varies slightly between normal and
high speed updating. The amount of difference depends on the
maximum speed, user scaling in menu 7, and the analog input 1 the filter
time. The worst case difference for analog input 1 is 0.12 % of full scale,
and for analog inputs 2 and 3 the difference is less than 0.12 % with a
maximum speed of 50 rpm or more. Typical differences (1500 rpm
maximum speed, menu 7 scaling of 1.000, analog input 1 filter of 4 ms)
are 0.015 % for analog input 1 and 0.004 % for analog inputs 2 and 3.
4.3.2 Hard speed reference update rate
The normal update rate for the hard speed reference is 4 ms, however it
is possible to reduce the sample time to 250 μs by selecting the
reference from particular sources. The fast update rate is only possible
provided the conditions given below are met.
Analog inputs (not including I/O expansion Solutions Module)
The analog inputs must be in voltage mode with zero offset
Limitations are the same as for the references via menu 1 described
above.
Applications and fieldbus Solutions Modules
For faster update rate Pr 91.03 must be used (this parameter is only
visible from the Solutions Modules). Any value written to Pr 91.03 is
automatically mapped into the hard speed reference Pr 3.22.
Encoder reference
It is possible to use the drive encoder as the source for the hard speed
reference. To do this the drive encoder reference destination (Pr 3.46)
should be routed to the hard speed reference parameter. If, and only if,
the maximum drive encoder reference (Pr 3.43) is set to the same value
as the maximum reference value (MAX_SPEED_REF), and the scaling
(Pr 3.44) is 1.000, the drive takes the encoder pulses directly. This gives
a form of reference slaving where the integral term in the speed
controller accumulates all pulses from the reference and tries to match
them to the feedback from the motor encoder. Pulses are lost if the
reference reaches a minimum or maximum limit including zero speed in
unipolar mode. The reference is sampled every 250 μs. It is possible to
apply scaling even in this high speed update mode by changing the
number of encoder lines per revolution. It is also possible to use this high
speed update mode with some position feedback category Solutions
Modules (see description for the appropriate Solutions Module.)
4.3.3 Torque reference update rate
The normal update rate for the torque reference (Pr 4.08) is 4 ms,
however it is possible to reduce the sample time to 250 μs by selecting
the reference from particular sources.The fast update rate is only
possible provided the conditions given below are met.
Analog inputs 2 or 3 on the drive
The analog inputs must be in voltage mode with zero offset.
3.03 Speed error
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
1 11111
Range ±SPEED_MAX rpm
Update rate 4 ms write
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