Programming Your Application
6-33
650S AC Drive
A Method for Setting-up the PI Gains
The gains should be set-up so that a critically damped response is achieved for a step change in setpoint. An underdamped or
oscillatory system can be thought of as having too much gain, and an overdamped system has too little.
To set up the P gain, set the I gain to zero. Apply a step change in setpoint that is typical for the System, and observe the
response. Increase the gain and repeat the test until the system becomes oscillatory. At this point, reduce the P gain until the
oscillations disappear. This is the maximum value of P gain achievable.
If a steady state error is present, i.e. the feedback never reaches the setpoint value, the I gain needs to be increased. As before,
increase the I gain and apply the step change. Monitor the output. If the output becomes oscillatory, reduce the P gain slightly.
This should reduce the steady state error. Increasing the I gain further may reduce the time to achieve zero steady state error.
These values of P and I can now be adjusted to provide the exact response required for this step change.
Auto Restart
Parameters
S
ST21 to
S
ST24 provide the facility to automatically reset a choice of trip events and restart the drive with a
programmed number of attempts. If the drive is not successfully started, a manual or remote trip reset is required.
The number of attempted restarts are recorded. This count is cleared after a trip-free period of operation (5 minutes or 4 x
AUTO RESTART DELAY, whichever is the longer); or after a successful manual or remote trip reset; or by removing the
Run signal (Terminal 7, DIN1).
Refer to Chapter 7: "Trips and Fault Finding" - Hexadecimal Representation of Trips.
Underdamped (oscillatory)
Critically Damped
Overdamped
OUTPUT
SETPOINT
