Rockwell Automation 7000 PowerFlex Medium Voltage Air-Cooled (B Frame) Installation - ForGe Control - Manual (Page 77)

Rockwell Automation Publication 7000-IN007E-EN-P - June 2014 77
General Reference Appendix A
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 N•m (lb•ft)
• W = force N or kg f (lb)
• K = gyration radius m (ft)
• WK 2 = total system inertia (kg f x m2 [lb•ft2 ] ) that the motor must
accelerate, including motor, gear box, and load
• t = time (s) 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 14 - Typical Application Load Torque Profiles
Table 15 - 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
Screw type, loaded CT 200 100 100 Contact factory Yes
DRAG LINE CT 100 200 200 Contact factory Yes