<VV> RE: VirtualVairs digest, Vol 1 #580 - 8 msgs

JVHRoberts@aol.com JVHRoberts@aol.com
Tue, 15 Jun 2004 19:08:40 EDT


Actually, a fairly efficient 5 HP Electric motor should draw only about 17 
amps at 240 volts. There are farm duty electric motors up to 20 HP that'll run 
on 240 volts, single phase! 
The peak HP thing is a joke. I have no idea why they call it that. However, 
direct drive small displacement compressors are somewhat more efficient than 
the old belt driven units. 


In a message dated 6/15/2004 5:45:28 PM Eastern Standard Time, 
srmarti@netzero.net writes:
I never understood how they got away with the horsepower claim.  I have a
real 5 hp motor driving my air compressor. That's about as much as practical
for single phase 220vac.  You can sandblast your whole car with it in a
weekend, or run a correctly sized blast cabinet all. day.  It simply isn't
possible to run that big a motor on residential 110vac.

It's about 746 watts/hp or 3730 watts.  That means a current draw of about
34 amps.  That's wrongly assuming the motor is 100% efficient.  Maximum for
110vac is typical 15 or 20 amps.  That why none of the plug in electric
heaters are more than 1500 watts.

The peak hp number can't have any meaning in the real world.  Just how long
could this peak power be produced?  A fraction of a second?

Pity the poor trusting customer that doesn't do the math.
They should the a lawsuit about this one.  IMHO it's fraud.

Steve Marti