Doug Miller wrote:
In article , Aaron Fude wrote:
When translating amps to hp for a 120V appliance, is the formula essentially

120*amps/745.699872

That would give a 15amp ryobi table saw a rating of 2.41hp which is
ridiculously high, no? Is my formula not right, or is 2.41hp not
ridiculous or is there something else I'm missing?

You're missing two things:
1) The amperage rating on any electric motor represents the locked-rotor
current, i.e. the current it draws when the rotor is unable to move. This is
*much* higher than the current the motor draws when it's in operation, and is
in no way representative of the motor's actual power output.

Nope. The nameplate will have the running amps at rated HP. Overload
protection of may motors is based on the nameplate current rating.
(Many motors also have a "service factor" greater than one which means
the motor can be operated at higher current (and HP) at a little shorter
life.)

Motors typically have a code letter for locked rotor amps. Locked rotor
amps is about 6x the running amps. Unlikely the running amps for a table
saw is 2.5A. (An even 15A is probably not a motor current rating.)

The "lie" in motor HP *may* be the max HP you can get from the motor
before stall (which which would be a lie), which you might very
occasionally use. Wouldn't think that would make sense for a shop vac.

2) You're also assuming 100% efficiency, which will never be the case. There
will always be some losses due to friction in the bearings, etc.

Quite right.

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bud--