motor amps ?

[lahola1]

My Powerkraft RAS is only drawing 3.6 amps. I just found the motor tag and it says 2HP, 13.0 amps. How is this possible?
BTW, the 20,000 RPM output shaft for router bits works really nice.

[Hobbyman2]

max / full load rating ?

[edma194]

How are you measuring the current draw? As suggested above, it could draw far less than 13 amps if not fully loaded like it would be sawing through heavy stock. To just keep a tool spinning should not require much current once it gets up to speed.

[JPG]

20k rpm? My guess is that it has a universal motor(AC/DC is a clue also) that is geared down to the saw arbor.

Light/no load will result in much lower current draw.

Quit sweating!

[lahola1]

My SSMKVII draws 10.7 amps, no load and my craftsman RAS motor tag says 11.0 amps and it draws 11 amps, no load. IIRC I tried ripping a 2x4 on the powerkraft and there was no way it had had enough power to rip it. My Craftsman could. Can something go bad in the motor that can cause this? As I have said before, I am no electric expert.

[DLB]

My SSMKVII draws 10.7 amps, no load and my craftsman RAS motor tag says 11.0 amps and it draws 11 amps, no load. IIRC I tried ripping a 2x4 on the powerkraft and there was no way it had had enough power to rip it. My Craftsman could. Can something go bad in the motor that can cause this? As I have said before, I am no electric expert.

I'd say the answer is yes, but I'm no universal motor expert. The something would likely be electrical resistance, I'd start with brushes and cleaning the carbon off the armature where the brushes contact (commutator, IIRC). I think there are some spray cleaners specifically for that without disassembly beyond taking the brushes out. This is common in brushed motors because of normal arcing. But not the only potential source of resistance.

Induction motors, like in your SS, do draw a lot of no load amps but are not consuming all that power. This gets complicated fast, but with AC Volts times Amps only equals (or even indicates) watts with resistive loads.

- David

[lahola1]

JPG, you are correct. The motor turns at 20k and is geared down for the saw arbor. I guess I can live without ripping 2x4s on it . Just didn't make sense to me.
Thanks for all the replies.

[Hobbyman2]

Here is a link from Fluke , just a few things to inspect and test if you feel something is wrong .

https://www.fluke.com/en-us/learn/blog/ ... lfunctions

[JPG]

Universal motor marketers like to tout 'developed' horsepower.

Sorta like "peak' power.

Induction motors 'deliver' horsepower.

[DLB]

Universal motor marketers like to tout 'developed' horsepower.

Sorta like "peak' power.

Induction motors 'deliver' horsepower.

I love/hate where this is going. At 115 V and 13 Amps, electrical power in watts for AC is theoretically between 0 and 1495 Watts. If those VA numbers are valid for DC, it is exactly 1495 W. So at ~100% efficiency and a power factor of 1, neither possible for AC, that would be converted to 1495 mechanical watts aka 2.00 HP delivered. If real efficiency and PF are 0.8 (a guess) you're still well over 1-1/8HP delivered, a useful standard for this forum.

Anyone know if those cheap plug-in power meters actually measure electrical watts, as opposed to volt-amps, and will they work on a motor (start current) and/or non-sinusoidal (PowerPro) load?

Since real power is not known, shouldn't we sort of expect a stationary saw with a 13 Amp motor to rip a 2X assuming a sharp rip- or combo- blade and creation of a reasonable kerf? Not as well as a 2 HP induction motor, but kind of as a minimum capability. Therefore perhaps not drawing 13 Amps at full load. I'm back to brush/commutator as a logical starting point for any brushed motor.

- David