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Rockwell Automation Publication 7000L-UM301F-EN-P - March 2020
Appendix A
Catalog Number Explanation
Glossary of Terms
Breakaway Torque
Torque required to start a machine from standstill.
Accelerating Torque
Torque required to accelerate a load to a given speed, in a certain period of time.
The following formula may be used to calculate the average torque to accelerate a
known inertia (WK
2
):
T = ( WK
2
x change in RPM) / 308t
where,
T
= acceleration torque in (lb-ft).
WK
2
= total system inertia (lb-ft
2
) that the motor must
accelerate, including motor, gear box, and load.
t
= time (seconds) to accelerate total system load.
Steady State Torque
Continuous operating torque required to control the load, without instability.
Torque Limit
An electronic method of limiting the maximum torque available from the motor.
The software in a drive typically sets the torque limit to 150% of motor rated
torque.
Table 33 - Typical Application Load Torque Profiles
(1)
Application
Load Torque
Profile
Load Torque as Percent of Full-Load Drive Torque
Required Drive
Service Duty Rating
Encoder Required for
Extra Starting
Torque?
Break-away
Accelerating
Peak Running
AGITATORS
Liquid CT
100
100
100
Heavy
Yes
Slurry
CT
150
100
100
Heavy
Yes
BLOWERS (centrifugal)
Damper closed
VT
30
50
40
Normal
No
Damper opened
VT
40
110
100
Normal
No
CHIPPER (WOOD)—
starting empty
CT
50
40
200
Contact factory
No
COMPRESSORS
Axial-vane, loaded
VT
40
100
100
Normal
No
Reciprocating, starting
unloaded
CT
100
100
100
Contact factory
Yes
CONVEYORS
Armored face
CT
175
150
200
Contact factory
Yes
Belt type, loaded
CT
150
130
100
Heavy
Yes
Drag type
CT
175
150
100
Contact factory
Yes
