According to :
On Tue, 10 Jul 2007 17:40:08 -0000, (Chris
Lewis) wrote:
According to Meat Plow :
I used to work with Baldor repulsion/induction motors in the oilfield.
There were all 240v, 15 hp. If memory serves, on the well upstroke they
drew around 30 amps and otherwise around 18.
240V at 30A is 7200W, which means that during the upstroke those
motors were delivering somewhere around 6-8 HP. Conservative
motor selection, given that weather/rig conditions etc could cause
the motor to need more.
It would have been interesting to compare that with the motor
plate ratings, or know what size the fuses/breakers were.
Don't let that theoretical 800w per HP confuse you.
In case it wasn't clear, I wasn't confused ;-)
Motors never get
close to that efficiency. A typical 1HP motor will pull more like
12-13a @ 120v (my C/H compressor) and some cheap ones will be more
like 15-16a.
Once you get into multi-horsepower industrial-grade motors,
rule-of-thumb is about 1000 watts per HP. At 1-2HP and below,
they're not as efficient and 12-13A/HP is a reasonable ballpark at
the high end. Once you get to 1/4HP and below, motors can be
stupidly inefficient. Eg: the 1/4HP motor I saw whose label
said 10A.
--
Chris Lewis,
Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.