Deliberate O/L Due to Motor Service Factor?
Deliberate O/L Due to Motor Service Factor?
(OP)
My greetings to all
Is it correct, that for a given 100% mechanical load, a motor of a lower HP rating maybe used as long as the overloading does not go beyond the motor service factor?
For example, I have a 80HP mechanical load, say a 100HP at S.F. = 1.0 could have been sufficient, but one may say that a 75HP motor at S.F. = 1.15 can be used.
Is this correct even if the motor will be operated continuously at 80HP?
Is it correct, that for a given 100% mechanical load, a motor of a lower HP rating maybe used as long as the overloading does not go beyond the motor service factor?
For example, I have a 80HP mechanical load, say a 100HP at S.F. = 1.0 could have been sufficient, but one may say that a 75HP motor at S.F. = 1.15 can be used.
Is this correct even if the motor will be operated continuously at 80HP?





RE: Deliberate O/L Due to Motor Service Factor?
RE: Deliberate O/L Due to Motor Service Factor?
The service factor rating is intended to account for unknowns and unexpected changes in loading, generally brief in nature.
David Castor
www.cvoes.com
RE: Deliberate O/L Due to Motor Service Factor?
Is this a critical load?
Then consider the stability of the energy supply, are low voltage conditions common?
Will this motor run 24/7, 40 hours per week or less.
What are the costs and difficulties if the motor must be up sized to 100 HP at a later date? (The load information may not have been precise). Is it a "drop-in" change or must mounts and gearboxes be changed.
Location, is this motor close to the service or is it on the end of long conductors where voltage drop may be a factor.
I may compare the frame sizes of a 75 HP/SF 1.0, a 75 HP/SF 1.15 and a 100 HP/SF 1.0 motor.
Lastly compare the price.
Some may consider it prudent to consider these factors whenever a motor is to be closely matched to load requirements.
After determining and considering these factors you may make an informed decision and justify your decision should your design be challenged.
Bill
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"Why not the best?"
Jimmy Carter
RE: Deliberate O/L Due to Motor Service Factor?
I have done it. ... Ran a 10HP CNC spindle at 13HP for 6 seconds during a much longer cycle, as documented allowable by the CNC supplier. Great fun putting aluminum chips on the ceiling...
Mike Halloran
Pembroke Pines, FL, USA
RE: Deliberate O/L Due to Motor Service Factor?
Bottom line, what you decide on will have long term effects on total cost of ownership and that should be given MORE weight than initial capital expense in my humble opinion.
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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RE: Deliberate O/L Due to Motor Service Factor?
thread237-161272: Service Factor