ABB ACS280, Firmware Manual, Page: 48 / 430

48 Program features
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User load curve
The User load curve provides a supervisory function that monitors an input
signal as a function of frequency or speed, and load. It shows the status of the
monitored signal and can give a warning or fault based on the violation of a user
defined profile.
The user load curve consists of an overload and an underload curve, or just one
of them. Each curve is formed by five points that represent the monitored
signal as a function of frequency or speed.
In the example below, the user load curve is constructed from the motor
nominal torque to which a 10% margin is added and subtracted. The margin
curves define a working envelope for the motor so that excursions outside the
envelope can be supervised, timed and detected.
An overload warning and/or fault can be set to occur if the monitored signal
stays continuously over the overload curve for a defined time. An underload
warning and/or fault can be set to occur if the monitored signal stays
continuously under the underload for a defined time.
Overload can be for example used to monitor for a saw blade hitting a knot or
fan load profiles becoming too high.
Underload can be for example used to monitor for load dropping and breaking
of conveyer belts or fan belts.
Motor torque / Nominal torque
1
2
3
Output frequency (Hz)
1 = Overload curve (five points)
2
= Nominal process load curve
3 = Underload curve (five points)
1.2
1.0
0.8
0.6
0.2
0.4
0.0
-0.2
0 10 20 30 40 50