Specifications

2.8.11 Tuning the Closed Loop Controller

Once the closed loop controller has been set up, the

performance of the controller should be tested. In many

cases, its performance may be acceptable using the default

values of CL-93 PID Proportional Gain and CL-94 PID Integral

Time. However, in some cases it may be helpful to

optimize these parameter values to provide faster system

response while still controlling speed overshoot.

2.8.12 Manual PID Adjustment

1. Start the motor.

Set CL-93 PID Proportional Gain to 0.3 and

increase it until the feedback signal begins to

oscillate. If necessary, start and stop the

frequency converter or make step changes in the

set-point reference to attempt to cause

oscillation.

3. Reduce the PID proportional gain until the

feedback signal stabilizes. Reduce the propor-

tional gain by 40-60%.

Set CL-94 PID Integral Time to 20 sec. and reduce

it until the feedback signal begins to oscillate. If

necessary, start and stop the frequency converter

or make step changes in the set-point reference

to attempt to cause oscillation.

5. Increase the PID integral time until the feedback

signal stabilizes. Increase of the integral time by

15-50%.

CL-95 PID Differentiation Time should only be used

for fast-acting systems. The typical value is 25%

of CL-94 PID Integral Time. The differential

function should only be used when the setting of

the proportional gain and the integral time has

been fully optimized. Make sure that oscillations

of the feedback signal are sufficiently dampened

by the low-pass filter for the feedback signal

(parameters 6-16, 6-26, 5-54 or 5-59 as required).

Introduction VLT® HVAC Drive FC 102 Design Guide

38 MG16C102 - Rev. 2013-08-20