ABB ACQ580, Firmware Manual

Page: 56 / 422

52 Program features

User load curve (Condition monitoring)
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 stuck pump or dirty impeller.
Underload can be for example used to monitor for load dropping and for a blockage in
pump inlet (suction side).
The load curve can be used as a trigger for the pump cleaning function. (Underload =
blocked inlet on the pump, Overload = blockage in the pump impeller or output of the
pump).
Motor torque / Nominal torque
1
3
2
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
Output frequency (Hz)