4 Sep
2009
4 Sep
'09
5:16 p.m.
On Fri, Sep 4, 2009 at 6:20 PM, Chuck Guzis<cclist at sydex.com> wrote:
So, in today's "who gives a damn about what
ratings really mean"
world, exactly what does a 3.5 HP rating mean? ? My table saw has a 3
HP rating on the capacitor-start motor nameplate and there's no way I
could run it from a 120V circuit without popping a breaker, if that
was even possible.
Is it like the rating on consumer vacuum cleaners--12 amps, but only
if you stick a crowbar into the works and lock the rotor?
I'm seriously into woodworking. The subject of "marketing" horsepower
comes up all the time. Basically, there's two horsepower ratings.
One is the rating that generally gets applied to induction motors like
on larger woodworking machinery. The other generally gets applied to
universal motors. How do you tell the difference? Induction motors
are bigger and hum nicely and quietly. Universal motors are smaller,
but sound like 1000 eviscerated cats, loud enough to wake the dead.
That marketing horsepower rating is technically, under a very specific
scenario, correct.... believe it or not. But it's a useless number.
IIRC, it comes from the power spike that happens right when you grab
the shaft of the motor. So essentially, it's a useless power rating.
I might be off on the description. I'm not an EE and I got a
frightfully low grade in physics.
Don't believe anything sears says about horsepower ratings. They're
famous for making up their own horsepower terminology.
The absolute maximum that a typical 20amp 110v power line could
sustain is around 1.5hp. But that number is affected by other things
such as load on the motor and the length of the power cord. Just last
weekend, I installed a 100amp subpanel in my garage to power the wood
shop. I have 3 separate 220v lines, two are 30 amp and one is 20 amp.
The 30 amp lines are for the 5hp motor in the dust collector and the
6.5hp motor in the compressor. The 20 amp line is for the smaller 220
tools with 3hp motors. My biggest router is 3hp and plugs into a 110
line. ;-)
brian