4 HP on 115v??

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15 amps @ 120 volts = 2.41 horsepoer. They lie.

He
744.
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Figuring in efficiency and power factor, the best it's gonna be is ~1.5hp.
-- Al Reid
"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." --- Mark Twain

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No, the best it is ever going to be is 2.41 horsepower. Small motors are rated in INPUT power.

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CW wrote:

Ha! So _this_ is how Bosch routers went from 2HP to 2.25HP without a change in the motor!
--
gabriel

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The best the two organizations do is say that "this is what we would like you to do". If anybody followed that, we wouldn't have 6 HP shop vacs. That's why our customers used to bring us their motors for rebuld. They could either rebuild the old 2000 HP motor or they would have to buy a modern 3500 to replace it.

~1.5hp.
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All the more reason to use the amp rating instead of the HP rating. The amp rating is more strictly controlled.
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While that may be true, what is ultimately of importance is the power delivered to the shaft of the motor. That is where HP and torque are traditionally measured. What is better, a 15A motor with a 1.5 HP output or one with a 1 HP output. Efficiency and power factor must be considered. Input power is meaningless if you want to know how much work it will do.
--
--
Al Reid

"It ain't what you don't know that gets you into trouble. It's what you know
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On Wed, 21 Jan 2004 02:52:20 GMT, "Al Reid"

HP "where the rubber meets the road" is of course the only meaningful measurement. it's actually used in some high performance equipment, but output brake horsepower is not something I've ever heard of being measured on small electric motors. instead, the manufacturers seem to be free to engage in whatever flights of fancy they please when writing specifications.     Bridger
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writes:

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Yes, it is. In Europe, motors are rated in watts. That rating has to meet government standards.
writes:

like
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CW writes:

But it's still less than useful information because you have no idea of duty cycle or motor efficiency.
Charlie Self "Character is much easier kept than recovered." Thomas Paine
http://hometown.aol.com/charliediy/myhomepage/business.html
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Without RPM an torque curves, a horsepower rating is less than useful. The fact is, and the manufacturers know it, that 97% of the buying public would not understand these numbers if they gave them. A rating in true watts would be a standard at least. It sure beats the wildly variable horsepower claims they hang on them now.

duty
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By useing the same math that Porter Cable uses on my 7 HP air compressor, that draws 15 amps at 240 volts! Greg
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This is hilarious.
4.4HP * 746W = 3282.4W
3282.4W / 15A = 218.83V
If your 110/115/120V (however you want to rate it) circuit EVER reaches that, you're going to melt stuff in your house. Vpeak for 110Vrms is only about 155V. I've measured 125Vrms in the wall before, which is a peak of 177V.
In short, it is IMPOSSIBLE for that saw to ever develop 4.4HP, presuming its stall current is 15A, and it is running on a household 110V circuit (and further presuming that the motor is operating at 100% efficiency, which it is, of course, NOT).
Now, if it can draw 21A at Vpeak (155V) without turning in to a puddle, then it can consume power equivalent to 4.4HP, though it still wouldn't be cutting wood at that rating.

He
744.
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Al Reid wrote: "Still wrong since you are not taking efficiency and power factor in to account and you are using a ficticious voltage."
No, I'm not wrong. I said IF it could actually DRAW 21A at the peak voltage of 155V, then the math gives you power consupmtion of 4.4HP. Efficiency is not relevant, as I'm talking purely about consumed power (input power). Thus, if a 21A peak coincides with a 155V peak, the power consumption at that moment is 4.4HP. I am NOT talking about power delivered to the cutting teeth, or wherever else you may choose to measure it, I'm talking about the total consumed power of the machine.
And, 155V is not ficticious.......it's the peak instantaneous voltage for a 110V sine wave. (110VACrms / 0.707)
To quote myself:
"> Now, if it can DRAW 21A at Vpeak (155V) without turning in to a puddle, then

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voltage
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It is still meaningless. It is not a DC machine. It is still rated based on the RMS input voltage. Mow if you wnnt to apply a higher (155VRMS) input voltage, then you would be correct.
The only measure that has any value is the HP and torque at the output shaft. I don't care how many amps go in, I want to know how much HP is developed.

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On Wed, 21 Jan 2004 02:58:00 GMT, "Al Reid"

I doubt you will ever see that information given for a power tool. I suspect that that number would shock the american buying public, who think that they own 6 HP vacuum cleaners and such. I doubt that output HP on one of sears' 6 HP specials would exceed 1/4 HP or so....
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Check out this link for a series of properly rated motors:
http://www.marathonelectric.com/motors/mdata.asp?MAJ=DP&MIN &DAT=A
-- Al Reid
"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." --- Mark Twain
wrote:

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