Program features 49
User Load Curve
The User Load Curve (ULC) provides a supervisory function that monitors an input
signal as a function of speed and load. The ULC consists of an overload and an
underload curve, or just one of them.
Note: This feature is available only in vector control mode.
Some of the salient features of the ULC are:
• Formed by five points -The underload and overload curve are formed by five
points where the points represent monitored signal as a function of speed.
• Warning and/or fault for overload and underload - A warning and/or fault can be
displayed, if the monitored signal stays continuously over the overload/underload
limit for a defined time. You can define the time in parameter 37.41 ULC overload
timer/37.42 ULC underload timer and the action in parameter 37.03 ULC overload
actions/37.04 ULC underload actions.
• Sector based warning / fault - The five points makes four sectors and a warning
and/or fault can be displayed at each sector. This helps to find the speed range
that causes the fault or warning and the investigation can be performed
accordingly.
For example, overload can be used to monitor for saw blade hitting a knot or fan load
profiles becoming too high. Underload can be used to monitor for load dropping and
breaking of conveyer belts or fan belts.
The below graph shows the underload and overload points in a user load curve.
Overload area
Underload area
Allowed operating area
37.11, 37.31
(N1, OL1)
37.11, 37.21
37.12, 37.32
N2, OL2
37.12, 37.22
37.13, 37.33
N3, OL3
37.13, 37.23
37.14, 37.34
(N4, OL4)
37.14, 37.24
37.15, 37.35
(N5, OL5)
37.15, 37.25
overload/underload axis (current% or torque%)
Speed, N (rpm)
Sector 1 Sector 2
Sector 3
Sector 4
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