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power- Horsepower to watts

power- Horsepower to watts
by Roy O on 08/06/02 at 02:38:49

Yes I saw the conversion that 746 watts equalls 1 horsepower, but then that means that you could only get a maximum of 2 horsepower from a standard 15 amp outlet.  There are many electric motors that are 15 amps and can pump up to 6hp.  How is that possible with the formula 1 hp is 746 watts?

Re: power- Horsepower to watts
by Robert Fogt on 08/07/02 at 04:20:06

I found a list here:
[url]http://www.repair-home.com/info/electrical_material_guide.htm[/url]

It shows that a small appliance outlet could output up to 3840 watts at 240 volts. That would make about 5 hp motor max.

Maybe the motor manufacturers use different ways to measure the hp?!?!

You know how a 17 inch video monitor may only have a 16 inch viewable screen... Maybe they do something similiar with other electrical appliances to scam us into buying stuff. lol

Re: power- Horsepower to watts
by Noel on 08/26/02 at 23:40:19

Not all horsepower ratings are the same. The 746 watt figure is a direct conversion from reading power from one term of measurement to another.
When one looks at electric motors, lets use vacuum cleaners and table saws as examples, the HP rating advertised is a 'Rated HP' or 'Peak HP.  That rating is used solely for marketing purposes and really is quite deceptive.  The one figure you can use for accurate comparison is 'watts'. This is a measurement of the amount of electricity a particular circuit will consume  when it is operating in the manner the manufacturer designed.
Also, not all 5 HP motors are equal. There are many different types of motors, disigned for a broad variety of uses. Then there is the 'service factor'. Service factor measures the degree to which a motor can be overloaded for *very short*periods of time.  This is because not all motors are expected (designed) to start with the load already applied to the motor. A fan motor will generally have a lower service factor rating than a motor driving a conveyor belt. The fan motor has the weight of the fan blade and the air resistance (remember, air has mass, too) to get into motion. A motor driving a conveyor belt has the mass of the belt, whatever is ON the belt and the friction of the bearings to put in motion from a dead stop. Quite a bit more load on the conveyor motor than on the fan motor.
Keep in mind that these a broad general statements for the sake of comparision.

This is just an inkling of what your electrician must understand to be an electrician. I am an electrician. There is MUCH more info to know - or know where to find - than the average Joe/Jill would expect.

Re: power- Horsepower to watts
by Noel on 08/26/02 at 23:50:26

I failed to mention that by textbook definition a 15A 120 volt circuit is able to provide 1800 watts or 2.412 HP.  Since ALL electric motors are not 100% efficient - some of the electricity is converted into to heat, which is why they get warm in use - and have a degree of 'slip'
( the measurement of how much of the electricity actually causes the motor shaft to move with a load applied when compared to an identical motor that has no load).  This is part of motor design and is one reason that not all motors of a given HP rating are the same.

Re: power- Horsepower to watts
by Roy O on 08/29/02 at 02:57:35

746 watts = 1 horsepower
Are you sure that they are even meaning the electrical hp.  On one of the postings labled "Horsepower Gas v.s. Electric" it states that they are different.

If there is gas horsepower and electric horsepower which horsepower is the horsepower in the formula?

Re: power- Horsepower to watts
by Roy O on 08/29/02 at 03:08:55

I missed the fact that you already stated that;
"Not all horsepower ratings are the same. The 746 watt figure is a direct conversion from reading power from one term of measurement to another".
So Really I think the best way is just like you said is to go by watts.  But it frustating because for example if I'm looking through a Canadian Tire catalogue and am looking at tools I notice that routers, drill press's, and bench grinder's are in horsepower ratings, which leaves me in a more unfamiliar territory.  Glad to see that most other tools and ampliance's are rated in amps.

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