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Glossary of terms – Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C-Frame) - ForGe Control User Manual

Page 416

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416

Rockwell Automation Publication 7000L-UM301D-EN-P - June 2014

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

):

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