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3.4.2 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 par. 7-02
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:
Par
. 7
−
02 =
Total
inertia
kgm
2
x
par
. 1
−
25
Par
. 1
−
20
x
9550
x
Bandwidth
rad
/
s
Note: Par. 1-20
Motor Power [kW]
is the motor power in [kW] (e.g., enter ‘4’ kW instead of ‘4000’ W in the formula). A practical value for the bandwidth
is 20 rad/s. Check the result of the par. 7-02
Speed PID Proportional Gain
calculation against the following formula (not required if you are using a high
resolution feedback such as a sin-cos feedback):
Par
. 7
−
02
MAXIMUM
= 0.01
x
4
x
Encoder
Resolution
x
Par
. 7
−
06
2
x
π
x
Max
torque
ripple
%
A good start value for par. 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 par. 5-70
Term 32/33 Pulses per Revolution
(24V HTL on
standard drive) or par. 17-11
Resolution (PPR)
(5 V TTL on MCB102 Option).
Generally, the practical maximum limit of par. 7-02
Speed PID Proportional Gain
is determined by the encoder resolution and the feedback filter time,
but other factors in the application might limit the par. 7-02
Speed PID Proportional Gain
to a lower value.
To minimize the overshoot, par. 7-03
Speed PID Integral Time
could be set to approx. 2.5 s (varies with the application).
Par. 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.
3.4.3 Process PID Control
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.
The table 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.
par. 1-00
Configuration
Mode
par. 1-01
Motor Control Principle
U/f
VVC
plus
Flux sensorless
Flux w/ enc. feedb
[3] Process
N.A.
Process
Process & Speed
Process & Speed
Note: The Process Control PID will work under the default parameter setting, but tuning the parameters is highly recommended to optimize the application
control performance. The two flux motor control principles are specially dependant on proper speed control PID tuning (prior to tuning the process control
PID) to yield their full potential.
3 Introduction to AutomationDrive FC 300
FC 300 Design Guide
3-18
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