Pi Setpoint Ramp Times; Pi Controller Proportional And Integral Terms - Siemens MICROMASTER 420 Reference Manual

2.8.4

PI Setpoint ramp times

When PI control is enabled using P2200, the normal frequency ramp up and ramp
down times (P1120 and P1121) are bypassed. The PI setpoint has its own ramp
times, P2257 and P2258, which allow ramped PI setpoint changes.
The ramp up time, P2257, is active when the PI setpoint is changed or when a
RUN command is given. The ramp down time, P2258 is only effective on PI
setpoint changes. The ramp down times used after OFF1 and OFF3 commands
are set in P1121 and P1135 respectively.
2.8.5

PI Controller Proportional and Integral terms

The user can tune the performance of the PI controller to suit his process demands
by adjusting the P and I terms, P2280 and P2285. The demands of the process
will determine the optimal type of response, from a rapid recovery response with
overshoot to a damped response. By adjusting the P and I parameters it is
possible to achieve different types of response.
The following figures show how different responses to a 5% PI setpoint step
change on a pressure control system. The traces show the PI feedback signal,
with 1 V = 10%. The different responses are achieved by varying the settings of
P2280 and P2285.
Figure 2-4
14
Quick response with overshoot: P2280 = 0.30; P2285 = 0.03 s
MICROMASTER 420 Reference Manual
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