232 Rockwell Automation Publication 2198-UM001M-EN-P - November 2022
Appendix D Motor Control Feature Support
MotorWindingToAmbientCapacitance values to estimate the motor thermal
capacity based on the motor output current.
The MotorOverloadLimit attribute (default of 100%, max of 200%) can be used
to increase the motor overload trip-time by increasing the
MotorThermalOverloadFactoryLimit value. The MotorOverloadLimit should
be increased above 100% only if cooling options are applied. Increasing
MotorOverloadLimit does not change the behavior of MotorCapacity.
This thermal model supports setting the MotorOverloadAction attribute as
Current Foldback. Selecting the Current Foldback action results in a reduction
in the current reference via the MotorThermalCurrentLimit attribute value
that is reduced in proportion the percentage difference between the
MotorCapacity and the MotorOverloadLimit values.
When this thermal model is active, the MotorCapacity attribute is nonzero if
the motor output current is nonzero. The default
MotorThermalOverloadFactoryLimit and MotorThermalOverloadUserLimit
values for this thermal model are both 110%.
Speed Limited Adjustable
Torque (SLAT)
Speed limited adjustable torque (SLAT) is a special mode of operation that is
used primarily in web handling applications. While configured for SLAT, the
drive typically operates as a torque regulator. The drive can automatically enter
velocity regulation, based on conditions within the velocity regulator and the
magnitude of the velocity regulator's output, relative to the applied
TorqueTrim attribute.
A torque regulated application can be described as any process that requires
tension control. For example, a winder or unwinder with material being drawn
or pulled with a specific tension required. The process also requires that
another element set the speed.
When operating as a torque regulator, the motor current is adjusted to achieve
the desired torque. If the material that is being wound or unwound breaks, the
load decreases dramatically and the motor can potentially go into a runaway
condition.
The SLAT feature is used to support applications that require a robust
transition from torque regulation to velocity regulation (and vice versa). The
SLAT feature can be configured via the SLATConfiguration attribute as:
Direction of the applied torque and direction of the material movement
determine whether SLAT minimum or SLAT maximum mode should be used.
IMPORTANT This thermal model does not derate the motor-rated current when
operating at low speeds. Operating at low output frequencies does
not cause the MotorCapacity behavior to change.
Table 97 - SLAT Configuration Descriptions
Name Description
SLAT Disable SLAT function is disabled. Normal Velocity Loop operation.
SLAT Min Speed/Torque
Drive automatically switches from Torque regulation to Velocity regulation if
VelocityError < 0 and switches back to Torque regulation if VelocityError >
SLATSetPoint for SLATTimeDelay.
SLAT Max Speed/Torque
Drive automatically switches from Torque regulation to Velocity regulation if
VelocityError > 0 and switches back to Torque regulation if VelocityError <
SLATSetPoint for SLATTimeDelay.
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