Horse Power rating

On another thread I've shown pictures of a rebuild of a Parks Planer. I've got a question for some of you electricians.

The motor is huge compared to anything I've used. Pretty sure it's the original. There's no place where a horse power rating is marked. What is marked, in very faded numbers, is "10.6/5.3" and "115/230." I take this to mean the amps and voltage. That's pretty close to the 3/4 hp. motor on my bandsaw but it seems unlikely that this motor is that small.

Anybody have a guess as to the power of the motor?

John

To calculate the motor's power from those numbers you need to know the efficiency like this formula:

HP = V x I x Eff
746

If you motor is 65% efficient like my tablesaw motor is rated, you should have yourself a 1HP motor.

Most older motors were much larger than modern motors.

The older motors were made when the insulation used in the motors was not as good as insulation currently being used. The manufacturers had to produce motors that ran cooler that current motors so that the insulation would not fail. In order to keep the temperature down they used larger sizes of wire in the motors which also meant that the physical size of the motor had to be larger.

This is not necessarily bad. The old motor will be able to run cooler and will also not bog down as much during the motor start-up. However it is still a 3/4 to 1 HP motor.

Quote:

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Originally Posted by Ralph Barhorst

Most older motors were much larger than modern motors.

The older motors were made when the insulation used in the motors was not as good as insulation currently being used. The manufacturers had to produce motors that ran cooler that current motors so that the insulation would not fail. In order to keep the temperature down they used larger sizes of wire in the motors which also meant that the physical size of the motor had to be larger.

This is not necessarily bad. The old motor will be able to run cooler and will also not bog down as much during the motor start-up. However it is still a 3/4 to 1 HP motor.

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What he said :D.

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Originally Posted by Mike Marcade

To calculate the motor's power from those numbers you need to know the efficiency like this formula:

HP = V x I x Eff
746

If you motor is 65% efficient like my tablesaw motor is rated, you should have yourself a 1HP motor.

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That's not exactly the proper equation. You've lumped the Efficiency and Powerfactor into a single term. And while that can be effective when you are just estimating horsepower, there are motors that publish both their efficiency and/or powerfactor values. The proper form is:

HP = V x I x pf x Eff
________746

For a typical motor, the pf is 0.8, and the efficiency ranges from 0.8 to 0.9 (0.8 for a motor of this size and vintage).

Given these parameters, the OP's motor is only about 1.0 hp. (10.6 x 120 x 0.8 x 0.8)

Rick,

Your formula is defintely more accurate than mine. Now if we could just have him measure the torque and rpms than we would be all set. :)

Quote:

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Originally Posted by Mike Marcade

Rick,

Your formula is defintely more accurate than mine. Now if we could just have him measure the torque and rpms than we would be all set. :)

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OHHH...I get it now. I see from your signature line that you're one of those M.E. critters. :p Power doesn't make sense unless you can actually see it, right? That's alright, most M.E.'s I have met are like this. :D

Quote:

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Originally Posted by Rick Christopherson

OHHH...I get it now. I see from your signature line that you're one of those M.E. critters. :p Power doesn't make sense unless you can actually see it, right? That's alright, most M.E.'s I have met are like this. :D

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You are absolutely right, us gearheads don't work well with this abstract stuff. :D

Thanks guys for all the explanations. Seems a bit underpowered for such a heavy machine. Also, I think the handbook (from 1942) says a minimum of 2 hp. I guess I have to wait and try it out to see how it works.

John

I just checked all the documentation I've accumulated on Parks Planers. At different times the documentation suggests anywhere between 1/2 to 3 hp. One advertisement suggests 1 hp. for light use and 2 hp. for heavy use. As long as the motor runs well I'll probably be OK.

John