*
For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-
2192
51
there can be some oscillations that (hopefully) settle out after a time called the Settling Time. Remember
that as the output frequency changes, so does the pressure.
THE USER MUST DECIDE WHAT ARE
ACCEPTABLE RISE AND SETTLING TIMES.
The rise time, settling time, and overshoot are dependent on the system and can be adjusted by changing
three of the parameters in the table programming above: Proportional Gain, Integral Time, and Derivative
Time.
Some recommended PID values based on application type:
Process Variable
Proportional
Gain
Integral Gain
Anti-Hunting Gain
(seconds/repeat)
(seconds)
Flow 0.3 0.6 0.0
Levels: fast
1.0
8.0
0.0
Levels: slow
0.25
16.0
0.0
Pressure: fast
2.0
0.5
0.0
Pressure: slow
1.0
2.0
0.0
Temperature: fast
1.0
2.0
0.0
Temperature: slow
1.0
16.0
0.25
Temperature: furnace
0.8
8.0
0.125
Compressor speed
1.0
2.0
0.0
Simplified PID flowchart
(+)
Integral
Differential
+
+
new frequency reference to
drive main circuit
Proportional
Setpoint
(frequency
command that
develops
desired
process
condition)
error
(-)
+
Feedback (indicates actual process
condition)
V
error
= V
setpoint
- V
feedback
