4-195
xx1xb: PID output reversal). When the PID output is set for reverse operation the output frequency
decreased when the PID target value increases.
PID feedback value can be adjusted using parameter 10-04 (PID feedback gain) as well as with the analog
input gain and bias for terminal AI1 or AI2.
10-14: PID integral limit: Used to limit the integral output to prevent motor stall or damage to the system
in case of a rapid change in the feedback signal. Reduce the value of 10-14 to increase the inverter
response.
10-23: PID limit: Used to limit the output of the PID control. Maximum output frequency is 100%.
10-10: Primary delay time: Low pass filter situated after the PID limit block that can be used to prevent
PID output resonance. Increase the time constant to a value greater than the resonance frequency cycle
and reduce time constant to increase the inverter response.
10-09: PID bias: Used to adjust the offset of the PID control. The offset value is added to the frequency
reference as compensation. Use parameter 10-24 (PID output gain) to control the amount of
compensation.
In case the PID control output value goes negative, parameter 10-25 (PID reversal output selection) can
be used to reverse the motor direction.
Note: The PID output remains at zero when reverse operation is disabled.
10-26: PID target SFS: Sets the PID target value acceleration and deceleration ramp time. The PID target
SFS can be disabled by setting the multi-function digital inputs 03-00 ~ 03-05 to 36 (PID target SFS is off).
Reduce the acceleration / deceleration time in case load resonance or system instability is encountered.
PID Fine Tuning
All PID control parameters are related to each other and require to be adjusted to the appropriate values.
Therefore, the procedure achieving the minimum steady-state is shown as following:
(1) Increase or decrease the proportion (P) gain until the system is stable using the smallest possible
control change.
(2) The integral (I) reduces the system stability which is similar to increasing the gain. Adjust the integral
time so that the highest possible proportional gain value can be used without affecting the system
stability. An increase in the integral time reduces system response.
(3) Adjust the differential time if necessary to reduce overshoot on startup. The acceleration / deceleration
time can also be used for the same purpose.
Fine-tuning PID control parameters:
(1) Reduce overshoot
Output
Before
After
t
In case overshoot occurs, reduce the derivative time
(D) and increase the integral time (I).
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