NCCER horsepower calculation

Status
Not open for further replies.
G

Gary Shumaker

Member
In the level 2 NCCER text for electricians there is a formula for horsepower:
HP = load torque in ft.-lbs. x rpm / 5250.

I don't understand where the 5250 comes from and the book offers no explanation. The text also describes a change in horse power with altitude. I can make reasonable supositions about altitude since the less dense the air the less the motor is able to disipate heat away from the motor thereby allowing the metal in the motor to expand and create more internal friction (only a reasonable guess). Still, I don't understand where the divide by 5250 comes from. In case your interested the formula in on page 2.54 in the Level 2 version 2005 book.

Any help out there?
 
Constant

Constant

5250 is a constant (33000 / 2pi) used to convert HP units to torque (ft-lb) units and vis-versa - if using other units than ft-lbs, you use a diff constant
 
Last edited:
Okay. We're getting closer

Okay. We're getting closer

I get that 33000/2pi. However, what is the significance of 33000?
Regards,
Gary
 
5252 is a constant that translates the original definition of horsepower (1 HP = power required to move 150 pounds 220 feet in 1 minute) into rotary torque. Looking for an on-line derivation of this ...
 
Got it

Got it

Thank you.
I understand now. Too bad the NCCER book was so deficient in its explanation of this simple concept.

Thanks again,
Gary
 
Don't forget the horse!

Don't forget the horse!

Eons ago, someone decided that a standard horse could deliver 550 ft-lbs of energy per sec. Multiply that by 60 to obtain 33000 ft-lbs/min. Maybe they have a standard horse at the National Bureau of Standards?
 
Status
Not open for further replies.
Top