How can a 3ph router (actually 3.25hp) run on a 15 amp 120v circuit when a 3hp table saw required a 220v outlet?

Router: https://www.makitatools.com/products/details/RP2301FC

Tablesaw: https://lagunatools.com/classic/tablesaws/f3/

My guess is it has something to do with math.  The router is a smaller motor and spins at 22k RPM.

The principal is mansplained here.  You have to take into account the torque of the motor as well as how fast it can spin and apply that torque.  Table saw needs more torque for that bigass blade, but since the circumference of the blade is bigger, it needs less RPMs to generate the same speed at the cutting edge.

Lol, do you even torque, bro?

It's about motor amperage
If they were both run on 120v, the table saw would draw more amps.

The table saw probably has an actual 3 hp motor, could not find the amps for it.
The router is using smoke and mirrors; it draws 15 amps which is roughly 2hp.

There's a formula to convert amps to motor hp, it's a good shopping tool.

Amps don't actually convert to hp, but watts do. While 15 amps at 120v will give you about 1800 watts @ 1 watt = 0.0013404825737 hp you have about 2.4HPe. Though, at 20 amps, you do crack 3.21 HPe, which is about 3.26HPm. It isn't at all ridiculous, but it ultimately becomes about torque and service life.

ETA: accidentally hit submit before mentioning service factor. Modern motors can actually produce more horses than it's power suggests.

https://www.electricalengineeringtoolbox.com/2016/02/what-is-ac-motor-service-factor-sf.html

The router is measuring it's PEAK horsepower, when the universal motor is about to stall for the split second before the breaker trips.

The table saw is measuring it's RUNNING horsepower when the induction motor is under load, but not about to stall.

I have a 3HP Unisaw. The motor requires 240V and under full load it will draw ~12.2 amperes, or ~24.5 amperes at 120V. Under full load it will draw nearly 3,000 watts which is nearly 4HP. The router can realistically only draw about 1,800 watts before the breaker trips and that comes to about 2.5HP. Each horsepower is about 746 watts. Of course, these numbers aren't hard and fast and it isn't so clear cut because there are variables due to heat, resistance, voltage variances, changing loads, etc.

Shop vacs are the worst at this, claiming "6.5HP" when the spec plate says it draws 9 amps at 120 v. What they don't tell you is that "6.5HP" is measured when the rotor is locked and cooking from all the current it's drawing just before it catches fire.

A big thanks to everyone.

My old shop vac was labeled "5 hp (in small text) peak)" It pulled all of 103 CFM.

Maximum inrush current.


Shop vac did this before they died.  5 hp 120v vacuums.. Prosumer or light commercial dust collectors might not be that large.