￭ 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 1.7)
•
Nominal continuous current rating of the cable, specified by 35.61, and
•
Thermal time constant of the cable, specified by 35.62.
When the calculated temperature of the cable reaches 102% of the rated maximum, a
warning (A480) is given. The drive trips on a fault (4000) when 106% is reached.
Settings and diagnostics
Parameters: 35.60 Cable temperature...35.62 Cable thermal rise time (page 364).
Events: A480 Motor cable overload (page 559) and 4000 Motor cable overload (page 545).
￭ 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.
Program features 95
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