Rockwell Automation 150 MNL/SMC DIALOG+/APP-PROD GUIDE - Manual (Page 166)

10-4 Reference
Torque and Horsepower (cont.) Full-load Torque (FLT)
The full-load torque of a motor is the torque necessary to produce its
rated horsepower at full-load speed. In foot-lbs, it is equal to the rated
horsepower, multiplied by 5250, divided by the full-load speed in
RPM.
In addition to the relationship between speed and torque, the
relationship of current draw to these two values is an important
application consideration. The speed/torque curve is repeated below,
with the current curve added, to demonstrate a typical relationship.
Figure 10.3 Speed Torque Curve with Current Curve
Two important points on this current curve require explanation.
Full-load Current
The full-load current of an induction motor is the steady-state current
taken from the power line when the motor is operating at full-load
torque with rated voltage and rated frequency applied.
Locked-rotor Current
Locked-rotor current is the steady state current of a motor with th
rotor locked and with rated voltage applied at rated frequency.
NEMA has designed a set of code letters to define locked-rotor:
Kilovolt-amperes-per-horsepower (kVA/HP). This code letter
appears on the nameplate of all AC squirrel cage induction motors.
%
of
Full
Load
Torque
Pull Up Torque - PUT
Locked Rotor
Current
Breakdown Torque - BT
Synchronous Speed
Slip
Full-load Torque - FLT
Full Speed
Locked Rotor
Torque - LRT
Full-load Current