Pi Controller - Baldor 22H series Installation & Operating Manual

Section 1
General Information

PI Controller

MN722
Both the current and rate control loops are of the Proportional plus Integral type. If "E" is
defined to be the error signal,
E = Command – Feedback
then the PI controller operated on "E" as
Output = (K * E) + (K
p i
where K is the proportional gain of the system and K
p
The transfer function (output /E) of the controller using 1/s (Laplace Operator) to denote
the integral,
Output/E = K + K / s = K
p I
The second equation shows that the ratio of K
Baldor Series 22H AC Vector Control, the integral gain has been redefined to be,
K = (K / K ) / (2 ) Hz,
I i p
and the transfer function is,
Output/E = K (s + 2 K ) / s.
p I
This sets the integral gain as a frequency in Hz. As a rule of thumb, set this frequency
about 1/10 of the bandwidth of the control loop.
The proportional gain sets the open loop gain of the system, the bandwidth (speed of
response) of the system. If the system is excessively noisy, it is most likely due to the
proportional gain being set too high.
E dt)
(s + K /K ) /s.
p i p
/K is a frequency in radians/sec. In the
i p
Manual Tuning the Series 22H Control 6-3
is the integral gain of the system.
i