kW to HP

[gar]

101212-1650 EST

John120/240:

Was it James Watt who figured out that 746 watts = 1 horse power?

No.

James Watt was dead before the electrical unit watt was created. I can not find with clarity when the unit was created. But maybe between 1879 and 1882.

My search includes at least the references below.

"Menlo Park Reminiscences", Volume One, by Francis Jehl. In this book I do not find a reference to the unit watt. In 1879 in the development of the dynamo "Long-Legged Mary Ann" tests were run measuring output current, voltage, temperature rise, and input mechanical power.

At this time the measurment of electrical power as V*I was known. For a long time mechanical power, in HP, could be related to torque and speed. See James Watt below for foor-pounds per minute. See Joule below for power equation. I did not see a reference of physically how Edison related mechanical power input to electrical output. Joule's work may have provided this information.

History of Steam Engines:
http://en.wikipedia.org/wiki/Steam_engine

James Watt:
http://en.wikipedia.org/wiki/James_Watt

James Watt and Horsepower:
http://en.wikipedia.org/wiki/Horsepower

1882 The unit watt was recognized:
http://en.wikipedia.org/wiki/Watt

Origin and adoption as an SI unit
The watt is named after James Watt for his contributions to the development of the steam engine. The unit was recognized by the Second Congress of the British Association for the Advancement of Science in 1882. The 11th General Conference on Weights and Measures in 1960 adopted it for the measurement of power into the International System of Units (SI).

James Prescott Joule:
http://en.wikipedia.org/wiki/Joule's_laws
No mention of the unit watt here.

Other references:
http://nvl.nist.gov/docspub/NIST_Hi...r_III.__ELECTRICITY__RAILROADS__AND_RADIO.pdf

http://www.unc.edu/~rowlett/units/dictW.html

http://library.thinkquest.org/C006011/english/sites/watt_bio.php3?v=2
http://en.wikipedia.org/wiki/International_System_of_Units
http://www.french-metrology.com/en/history/history-mesurement.asp

http://www.google.com/search?q=hist...ine_result&ct=title&resnum=11&ved=0CEMQ5wIwCg


.

 

[ericsherman37]

[rant]
I welcome anything that does away with foot-lbs, Smoots, BTU's, and such. Ever study a "Yellow Tag" on an air conditioner?

Every time someone grouses about EU standards, I recall NBS/now NIST was founded 100+ years ago, after the Baltimore Fire, to solve incompatible firehose threads; and they still haven't won the battle. Meanwhile I pull the IEC powercord out of Item 2 on the bench and plug it into Item 3. The same cord!

[/rant]
But dual labels on a motor, KW in/KW out, would get no gripes from me.

I am 1.1194 smoots tall.

 

[LarryFine]

Gar, you're so lazy! Couldn't be bothered to do any real research, could ya? :roll:

:grin:​

 

[John120/240]

Gar, Thank You for the information. Pay no mind to ole Larry

 

[LarryFine]

Pay no mind to ole Larry

I follow that advice, too.

 

[Besoeker]

Gar, you're so lazy! Couldn't be bothered to do any real research, could ya? :roll:

:grin:​

Such a fine grasp of wit....

 

[gar]

101212-2340 EST

Larry:

I am rather lazy. I don't want to go over to the library and try to find some book that might tell me when the word Watt was first used as the unit of electrical power. However, it would be interesting to find out when and how this occurred. The Engineering Library contains over 600,000 volumes out about 9 million plus in the entire library system so there might be something there.

The dynamo was called a Faradic machine, and Eddy currents were called Foncault currents in 1879. It did not occur to them at this time to use a resistive shunt and measure the voltage. I believe they used a null balance method to measure voltage. Also in this year Edison and his employees discovered magnetic saturation.

http://en.wikipedia.org/wiki/Eddy_current

.

 

[Open Neutral]

The horsepower is based on the output power from a horse, so efficiency really doesn't come into it.

It does if you're the person mucking out the horse's stall!
Trust me on this.

Like motors, some horses are more efficient that others.

 

[Besoeker]

It does if you're the person mucking out the horse's stall!
Trust me on this.

Like motors, some horses are more efficient that others.

Then you might appreciate this:

 

[Besoeker]

101212-2340 EST

and Eddy currents were called Foncault currents

Foucault currents.
Have you read Foucault's Pendulum by Umberto Eco?