Toshiba G3 Workbook page 52

Note that PIDs for quickly-changing process variables have higher proportional gains than do their
counterparts for slowly-changing process variables. The higher the proportional gain, the smaller the rise
time. With increased proportional gain usually comes increased overshoot and increased chance of
Proportional Gain times V
Also known as reset, integral gain is not really a gain at all, but a time. The integral time (units seconds
per repeat) defines how long it takes the integral circuit output to go from zero to the level set by the
output of the proportional circuit. The integral action is therefore influenced by the proportional action.
The output of the integral circuit represents the area under the V
if V were to remain at the level shown, the output of the integral circuit would continue to increase
error
linearly with time (integral output is proportional to area of the rectangle = Proportional gain times V
times time). The shorter the integral time, the stronger the effect of the integral action. If you have a
system that never quite gets to the setpoint (there is steady-state error), decrease the integral time.
Proportional Gain times
For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-
PROPORTIONAL GAIN
oscillation.
Input to Proportional Circuit
V
error
Output of Proportional Circuit
error
INTEGRAL GAIN
Input to Integral Circuit
V
error
Output from Integral Circuit
Integral
Time
Time
Time
vs. time graph. In the below example,
error
Time
Time
2192
error
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