7.7 Motor Thermal Overload Protection
The control provides the motor thermal overload (TOL) protection feature for motor protection.
TOL prevents the motor from being subjected to excessive temperatures that could lead to
overheating.
This software model does not measure the motor temperature directly; it estimates the
temperature from available data and is dependent on the entered parameters being accurate.
The software model has no data about the ambient temperature at the location of the motor. For
critical applications, you must use a direct measurement method such as Resistance
Temperature Detectors (RTD) inside the motor.
Setting TOL Parameters
Refer to Limits Menu (1120) in Section Options for Motor Menu (1) of Chapter Parameter
Assignment / Addressing for parameters to set up TOL protection of the motor. The associated
parameters are:
• Overload select (1130)
• Overload pending (1139)
• Overload (1140)
• Overload timeout (1150)
• Speed derate curve (1151)
• Maximum motor inertia (1159)
You may select one of four options for the overload select parameter for motor protection.
Constant Mode
The rst option, "constant", is based on the current owing into the motor. A Motor Thermal
Overload Alarm 1 of an impending overload fault is issued as a warning, when the motor current
exceeds the overload pending parameter. A Motor Thermal Overload Alarm 2 is issued and a
thermal trip timer is started, when the drive current exceeds the overload setting. If this
condition is present for a period greater than the time set in the Overload timeout parameter,
the drive will trip and annunciate the event as Motor Thermal Overload Fault.
Note
Displaying motor thermal overload alarms
Alarms 1 and 2 must be enabled through the SOP for the drive to display these conditions.
Inverse time Modes
The second and third options, "straight inverse time" and "inverse time with speed derating", use
a software motor thermal model to determine motor temperature.
Operating the Control
7.7 Motor Thermal Overload Protection
NXGPro+ Control Manual
194 Operating Manual, A5E50491925A
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