Tuning Pid Speed Control; Process Pid Control - Danfoss VLT Decentral Drive FCD 302 Design Manual

Application Examples
Function
Selection of Motor Control Principle
5) Configure and scale the reference to the Speed Control
Set up Analog Input 53 as a reference Source
Scale Analog Input 53 0 RPM (0 V) to 1500 RPM (10 V)
6) Configure the 24V HTL encoder signal as feedback for the Motor Control and the Speed Control
Set up digital input 32 and 33 as encoder inputs
Choose terminal 32/33 as motor feedback
Choose terminal 32/33 as Speed PID feedback
7) Tune the Speed Control PID parameters
Use the tuning guidelines when relevant or tune
manually
8) Finished!
Save the parameter setting to the LCP for safe keeping
Table 4.18 Speed Control Settings

4.4.3 Tuning PID Speed Control

The following tuning guidelines are relevant when using
one of the Flux motor control principles in applications
where the load is mainly inertial (with a low amount of
friction).
The value of 30-83 Speed PID Proportional Gain is
dependent on the combined inertia of the motor and load,
and the selected bandwidth can be calculated using the
following formula:
Total inertia k gm 2 x par . 1 − 25
Par . 7 − 02 =
Par . 1 − 20 x 9550
NOTE
1-20 Motor Power [kW] is the motor power in [kW] (i.e.
enter '4' kW instead of '4000' W in the formula).
A practical value for the Bandwith is 20 rad/s. Check the
result of the 30-83 Speed PID Proportional Gain calculation
against the following formula (not required if you are
using a high resolution feedback such as a SinCos
feedback):
Par . 7 − 02 MAX =
0.01 x 4 x Encoder Resolution x Par . 7 − 06
x π
2
A good start value for 7-06 Speed PID Lowpass Filter Time is
5 ms (lower encoder resolution calls for a higher filter
value). Typically a Max Torque Ripple of 3 % is acceptable.
For incremental encoders the Encoder Resolution is found
in either 5-70 Term 32/33 Pulses per Revolution (24V HTL on
®
VLT Decentral Drive FCD 302
Parameter no.
1-01 Motor Control
Principle
3-15 Reference
Resource 1
6-1*
5-14 Terminal 32
Digital Input
5-15 Terminal 33
Digital Input
1-02 Flux Motor
Feedback Source
7-00 Speed PID
Feedback Source
7-0*
0-50 LCP Copy
x Bandwidth rad / s
x Max torque ripple %
®
MG04H102 - VLT is a registered Danfoss trademark
Setting
[3] Flux w motor feedb
Not necessary (default)
Not necessary (default)
[0] No operation (default)
Not necessary (default)
Not necessary (default)
See the guidelines below
[1] All to LCP
standard drive) or 17-11 Resolution (PPR) (5V TTL on
MCB102 Option).
Generally the practical maximum limit of 30-83 Speed PID
Proportional Gain is determined by the encoder resolution
and the feedback filter time but other factors in the
application might limit the 30-83 Speed PID Proportional
Gain to a lower value.
To minimize the overshoot, 7-03 Speed PID Integral Time
could be set to approx. 2.5 s (varies with the application).
7-04 Speed PID Differentiation Time should be set to 0 until
everything else is tuned. If necessary finish the tuning by
experimenting with small increments of this setting.

4.4.4 Process PID Control

The Process PID Control can be used to control application
parameters that can be measured by a sensor (i.e.
pressure, temperature, flow) and be affected by the
connected motor through a pump, fan or otherwise.
Table 4.19 shows the control configurations where the
Process Control is possible. When a Flux Vector motor
control principle is used, take care also to tune the Speed
Control PID parameters. Refer to the section about the
Control Structure to see where the Speed Control is active.
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