On Wed, 02 Jun 2010 22:50:43 -0500, "
wrote:

On Wed, 02 Jun 2010 21:26:25 -0400, wrote:

On Tue, 01 Jun 2010 22:06:49 -0500, "
wrote:

On Tue, 01 Jun 2010 22:11:40 -0400, wrote:

On Tue, 01 Jun 2010 20:36:38 -0500, "
wrote:

On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" wrote:

Quite a few technical electrical errors there but you concept is almost
correct.
A one HP motor make use of 748 Watts, not consumes.

Nope. A 1-HP motor *delivers* one horsepower of mechanical power
(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
"watts" is not capitalized).

120v X 10A = 1200va not watts
Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
one?

I don't believe you. A 1HP motor may require 1200W at full load, but not a
1/4HP motor.

It can draw 1200 watts at startup. Not terribly uncommon. When
rotating, a whole lot less.

Agreed.

The new 5HP motors are including the inertia of the rotor and do not specify
"how long" they can deliver that HP.

Nope. Well, maybe Crapsman's HP rating. ;-)

Foot lbs torque @ rpm- a heavy rotor or flywheel CAN deliver
significant horsepower for a matter of seconds - after it has been
brought up to speed. In SOME applications, a heavy flywheel will alow
a much smaller than normal motor to do the job.

Ok, but that's not the way motors are rated or HP is calculated.

...
which are you dissagreeing with?

Motor ratings include the energy from the flywheel.

Horsepower is measured as foot/lbs per second - RPM X Ft Lbs
Torque/5252 is horsepower. Period.

Ok, 550 ft*lbs/sec. I said that earlier.

And a heavy flywheel will allow a small motor to provide significantly
inproved torque for cyclic loads - making, is some cases, a 1/4 horse
motor do the job a 3 horse motor could not do without a flywheel.
Scaled up that's how punch presses work.

The motor will still be rated 1/4hp. That's its average output.

One electric HP is 745 watts, more or less - but to produce that 1 HP
with a motor of 80% efficiency requires 931 watts. And 80% isn't bad
for a "consumer equipment" motor.

80% is very optimistic.

And a series wound motor rated at, say 1 HP constant, may be able to
produce upwards of 4HP or more for periods of up to several minutes,
depending on it's thermal mass, and for duty cycles of up to say 15
or 20%. So that motor, rated at continuous service, is a 1HP motor,
and at cyclic service, perhaps legitimately 4 HP.

...but it's *not* a 4HP motor.

That said - if it is a 115 volt motor, running on a 15 amp circuit, it
is NOT more than a 2 HP motor - definitely - and more likely not more
than 1.5 if starting under no load or with a slow-trip breaker.

It's not even that. 1.5HP on a 20A circuit is believable.

Generally not more than 1 HP if it starts a load on a standard trip
breaker or fuse.

Ok, your point is?
What's YOUR point? In yopur last post you said that's not how motors
are rated and horsepower measured. Quote "Ok, but that's not the way
motors are rated or HP is calculated"

I just said it is, and you agreed with me except on the "specialty"
rating of some motors - which ARE rated as I said. A motor CAN have 2
ratings - a constant (average) HP rating and a peak (cyclic or short
duty) rating.

Also, the "real" 2HP Baldor Cap-start cap-run motor I have installed
on my compressor is rated at 20 amps at 115 volts and will start with
the unloader on a 15 amp slow-blow fuse unless it's cold out.
It is only about 65% efficient at full load, Like I said, 80% would
be a pretty good motor (I didn't say 80% was common - I was just
making the point that EVEN WITH an 80% efficient motor,1.5 or 2HP on a
115 volt 15 amp circuit would be MAXIMUM - anyone claiming higher than
that is "more than suspect".

THAT was the point I was making on the LAST post.