Reply by crank49

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Posted on Motor differences between Circular saws(120v/2.3hp) vs Table saw (120/1.5hp)?

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4032 posts in 2999 days

#1 posted 11-04-2011 03:29 PM

About the most true HP you can generate with a 120 volt, 15 amp circuit is 1.75 HP. I suppose with super attention to efficiency, the best bearings, the best wire, etc. you could get 2 HP; but that’s it.

How do you explain a shop vacuum with a big bold 3” tall label claiming 6.5 HP (peak, in tiny letters)?
Simple, they LIE.

Table saws usually have induction motors. They are designed to run all day at the rated power. If you overload an induction motor it will simply start to build up heat and eventually get so hot it burns the insulation from its wiring, shorts out and shuts down. If you designed the induction motor to run on 60 volts and then plugged it into a 120 volt circuit, 200% overvoltage, it would not create 200% more horse power, it would over heat more quickly and burn out faster.

Vacuums, routers, hand held circular saws, and even job site type table saws have universal, series wound motors. If you design one of these motors to run on 60 volts and then plug it into 120 volts it will overheat also, but while it’s running it is producing 200% more power than its rating. To overcome the overheating problem, the manufacturers install additional cooling fan capacity to bleed off most of the excess heat. In a shop vacuum the air coming through from the filter is routed through the motor to keep it from melting down. Hence, the exaggerated HP rating.

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