ABB ACS880-01 Series, Firmware Instructions

Page: 119 / 664

Program features 119

Thermal protection of motor cable
The control program contains a thermal protection function for the motor cable. This
function should be used, for example, when the nominal current of the drive exceeds
the current-carrying capacity of the motor cable.
The program calculates the temperature of the cable on the basis of the following
data:
• Measured output current (parameter 01.07 Motor current )
• Nominal continuous current rating of the cable, specified by 35.61 Cable nominal
current , and
• Thermal time constant of the cable, specified by 35.62 Cable thermal rise time .
When the calculated temperature of the cable reaches 102% of the rated maximum,
a warning (
A480 Motor cable overload ) is given. The drive trips on a fault ( 4000 Motor
cable overload ) when 106% is reached.
Settings
Parameters 35.60 … 35.62 (page 332 ).

User load curve
The 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
37.11 … 37.15 ) or frequency ( 37.16 … 37.20 ) 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 ( 37.21 … 37.25 ) and overload ( 37.31 … 37.35 ) 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.