ABB ACS550 Series, User Manual

Page: 160 / 310

160 ACS550 User’s Manual
Parameters
PID controller
–
Advanced
The ACS550 has two separate PID controllers:
• Process PID (PID1) and
• External PID (PID2)
Process PID (PID1) has 2 separate sets of parameters:
• Process PID (PID1) SET1, defined in Group 40: PROCESS PID SET 1 and
• Process PID (PID1) SET2, defined in Group 41: PROCESS PID SET 2
You can select between the two different sets by using parameter 4027.
Typically two different PID controller sets are used when the load of the motor
changes considerably from one situation to another.
You can use External PID (PID2), defined in Group 42: EXT / TRIM PID , in two
different ways:
• Instead of using additional PID controller hardware, you can set outputs of the
ACS550 to control a field instrument like a damper or a valve. In this case, set
parameter 4230 to value 0. (0 is the default value.)
• You can use External PID (PID2) to trim or fine-tune the speed of the ACS550.
Code Description
4001 GAIN
Defines the PID controller’s gain.
• The setting range is 0.1… 100.
• At 0.1, the PID controller output changes one-tenth as much as the error value.
• At 100, the PID controller output changes one hundred times as much as the error value.
Use the proportional gain and integration time values to adjust the responsiveness of the system.
• A low value for proportional gain and a high value for integral time ensures stable operation, but provides sluggish
response.
If the proportional gain value is too large or the integral time too short, the system can become unstable.
Procedure:
• Initially, set:
• 4001
GAIN
= 0.1.
• 4002
INTEGRATION TIME
= 20 seconds.
• Start the system and see if it reaches the setpoint quickly while maintaining stable operation. If not, increase
GAIN
(4001) until the actual signal (or drive speed) oscillates constantly. It may be necessary to start and stop the drive to
induce this oscillation.
• Reduce
GAIN
(4001) until the oscillation stops.
• Set
GAIN
(4001) to 0.4 to 0.6 times the above value.
• Decrease the
INTEGRATION TIME
(4002) until the feedback signal (or drive speed) oscillates constantly. It may be
necessary to start and stop the drive to induce this oscillation.
• Increase
INTEGRATION TIME
(4002) until the oscillation stops.
• Set
INTEGRATION TIME
(4002) to 1.15 to 1.5 times the above value.
• If the feedback signal contains high frequency noise, increase the value of parameter 1303
FILTER AI
1 or 1306
FILTER AI
2 until the noise is filtered from the signal.