Underload And Overload Protection - ABB +N5600 Firmware Instructions

52 ESP program features

Underload and overload protection

Load protection functions can constantly monitor selected load signal against defined
limit which are fixed along the motor speed range or vary according to the load curve
settings.
Each underload and overload protection function limit type can be configured
separately for the user defined any kind of work-zone in terms of load conditions.
Monitored signal (79.12) (79.42)
79.51 Overload
curve point 1 (%)
79.21 Underload
curve point 1 (%)
79.01 Load
curve speed
point 1
The custom user load curve provides a function that monitors an input signal (eg.
Motor torque or motor current) as a function of drive output speed or frequency. The
function includes both high limit (overload) and low limit (underload) monitoring.
Overload monitoring can, for example, be used to detect a pump becoming clogged
or a saw blade hitting a knot. Underload monitoring can detect the load being lost, for
example because of the snapping of a transmission belt.
The monitoring is effective within a motor speed and/or frequency range. The
frequency range is used with a frequency reference in scalar motor control mode;
otherwise, the speed range is used. The range is defined by five speed (parameters
79.01...79.05) values. The values are positive, but the monitoring is symmetrically
active in the negative direction as the sign of the monitored signal is ignored. Outside
the speed/frequency range, the monitoring is disabled.
An underload (79.21...79.25) and overload (79.51...79.55) limit is set for each of the
five speed or frequency points. Between these points, the limits are interpolated
linearly to form overload and underload curves.
79.02 Load
curve speed
(%) point 2 (%)
OVERLOAD
ALLOWED
OPERATION
UNDERLOAD
79.04 Load
79.03 Load
curve speed
curve speed
point 4 (%)
point 3 (%)
79.55 Overload
curve point 5 (%)
79.25 Underload
curve point 5 (%)
79.05 Load Speed
curve speed
Frequency
point 5 (%)