Question about motors

lifting a formula from a web site

HORSEPOWER= (V x A x EFF)÷746 EFFICIENCY= (746 x HP)÷(V x A)

Multiply Horse Power by 746w (1 HP = 746 Watts) Find Circuit Voltage and Phase Example:

an online calculator is here

in article TmwId.64407$ snipped-for-privacy@weber.videotron.net, Junkyard Engineer at snipped-for-privacy@engineer.com wrote on 1/22/05 9:50 AM:

That sounds about right.

In addition to the power factor correction, a single phase induction motor behaves like two motors in one. The first, the one that gives useful power, runs a bit slower than if it were synchronous. The second is being run backwards at close to synchronous speed. This is another hit on efficiency.

Bill

catalog (King

takes and they

the following :

something here like

doubt very much that

a cos phi

is usually what

a 1 HP motor.

You are close... type of motor though is a big issue, brush type, split phase capacitor start...or the ultra cheap versions with no capacitors used as in many of the chinese drill presses.... those lack even workable levels of torque.

They list amps because they are using chinese motors mostly and those are not rated in HP often but just running amps...and if you are not careful are cheap low torque motors with sleeve bearings...some of the brush types (high torque) with PLASTIC brush holders for the hand tool motors.... the brush holders *melt in about half an hours run time... in some but not all cases... I had that with a 12 dollar 3/8" drill. Junk. but it drilled 12 dollars worth of holes none the less when I needed multiple drills laying around the job site.

My dewalt 3/8" drill cost 80 dollars 15 years ago, it still runs strong, twice the torque of the chinese drill/// and has drilled a million dollars worth of holes. Its so old now the rubber cord got hard and cracked I have to put a new cord on it.

My craftsman 3/8 drill got sunk with a clients house boat into salt water for a week.... I dried it out on the dock... it still works great...it is 15 or 20 years old.... though the chuck needed a little loosening up. The chinese tools were toast. Bearings shot. etc.

For tools you are going to use a lot ... buy good ones...if you use a tool rarely and need it for logistics issues only..say one pipe thread on site...or on the truck just in case you need the capability....then a cheap tool is the way to go in some but not all cases.

Phil Scott

----------- You are assuming that the motor is at unity pf- it isn't. Consideriing an efficiency of 75% and a power factor the same, and estimating full load pf about the same (0.8) then

Thanks guys, you surely saved me some headaches.

I'm so tired of all those chinese stuff reminds me of the 60-70's when everything was made in Japan.

But you know what, I'm not so sure that we have to blame Chinese companies. It would certainly be those F*** marketing gurus here that think that we would be pissed off to pay 50$ more for a decent motor on an equipment. I would guess that it's a woman who is marketing director that do not care about men's stuff.

"Phil Scott" a écrit dans le message de news: 1ezId.4695$ snipped-for-privacy@newssvr14.news.prodigy.com...

scanning the internet for a formula was so much easier then walking over to a bookshelf. alas often accuracy and completeness are sacrificed.

i wonder how future generations will fare when they discover the only source of data is only approximately correct.

The engineers will cope- the rest of the world will argue on the basis of lack of knowledge