Selection Of Motor Thermal Models; Generic Motors - Allen-Bradley Kinetix 5700 User Manual

Appendix E Motor Control Feature Support
Selection of Motor Thermal
Models
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The Kinetix 5700 drives contain two motor thermal-overload protection
algorithms that you can use to prevent the motor from overheating.

Generic Motors

The default thermal model is a generic I
algorithm. This model is active if the MotorWindingToAmbientResistance or
the MotorWindingToAmbientCapacitance values are 0.0. The purpose of this
algorithm is to limit the time a motor is operating with excessive levels of
current. The relationship between Motor Overload Factory Limit trip-time
and motor output current is shown in
Figure 228 - Motor Overload Curve
100,000
10,000
1000
100
10
0 100 125
You can use the MotorOverloadLimit attribute (default of 100%, max of
200%) to increase the motor overload trip-time by artificially increasing the
motor rated current (for thermal protection only). MotorOverloadLimit
should only be increased above 100% if cooling options are applied. Increasing
MotorOverloadLimit causes MotorCapacity to increase more slowly.
The generic motor thermal model also derates the motor rated current (for
thermal protection only) when operating at low speeds. The derating factor is
30% at 0 Hz and 0% at 20 Hz, with linear interpolation between. Operating at
output frequencies less than 20 Hz causes MotorCapacity to increase more
quickly.
When the generic motor thermal-model is active, the MotorCapacity attribute
increases only if the motor output current is greater than the effective motor
rated current (taking into account the MotorOverloadLimit and low speed
derating factor). The default MotorThermalOverloadFactoryLimit and
MotorThermalOverloadUserLimit values for this thermal model are both
100%.
IMPORTANT The generic motor-thermal model does not support Current Foldback as
a Motor Overload Action.
Rockwell Automation Publication 2198-UM002G-EN-P - February 2019
2
T Class 10 overload protection
Figure 228.
250
175 200 225
150