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Diagnostics Optimization CT MODBUS RTU Technical Data
E300 Design Guide 13
Issue Number: 1
2.4.1 Typical short term overload limits
The maximum overload limit changes depending on the selected motor. Variations in motor rated current, motor power factor and motor leakage
inductance all result in changes in the maximum possible overload due to the thermal models estimation of the motor temperature as a percentage of
its maximum allowed temperature. Typical values for overload are shown in the table below:
Table 2-3 Typical overload limits
Operating mode Closed loop from cold Closed loop from 100 % Open loop from cold Open loop from 100 %
Heavy Duty overload
Motor rated current = drive rated
current
175 % for 40 s 175 % for 5 s 150 % for 60 s 155 % for 8 s
Heavy duty operating mode
The thermal protection is set to protect force ventilated induction motors and permanent magnet servo motors by default. If the application uses a
self ventilated (TENV/TEFC) induction motor and increased thermal protection is required for speeds below 50 % base speed, then this can be
enabled by setting Low Speed Thermal Protection Mode (B44) = On (1).
Operation of motor I
2
t protection
Motor I
2
t protection defaults to be compatible with:
• Forced ventilation induction motors
• Permanent magnet servo motors
Total Output Current (J22)
as percentage of motor
rated current
Motor speed as a
percentage of base speed
100 %
Max. permissible
continuous
current
100 %
I t protection operates in this region
2
70 %
50 %
B44
B44
=0
=1
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