Electric motor 1725 VS 3450

[fRED mCnEILL]

I am looking ar replacing a 3450 rpm electric motor in my tablesaw with a motor that spins at 1725. If I go with a different pulley to maintain the same speed at the blade as I now have will this reduce the power of the saw. I think I know the answer but want to confirm it.

Thx

Fred

[Frank Pratt]

As long as the HP rating is the same with the new motor, the power at the blade will be the same.

[Jim Bowers]

Stick with the same rotational speed. This saw was designed to rotate at 3450 rpm. This faster the blade the smoother the cut. There is a lot of physics involved in determining what the saw blades forward speed should be. Yes 5 hp is 5 hp. However, it is important to maintain the forward speed of the blade. Keep the same rotational speed

[Larry Edgerton]

Fred, I get what you are going for, changing pulley size to get back the same speed, but you have to think of leverage. with the larger pulley it will require twice the torque to maintain speed in a cut because of the larger pulley size, so I would stick with the same RPM. now, if you doubled the HP/torque you would be in the same ballpark. I take it you have a motor you want to use?

[Rod Sheridan]

Fred, I get what you are going for, changing pulley size to get back the same speed, but you have to think of leverage. with the larger pulley it will require twice the torque to maintain speed in a cut because of the larger pulley size, so I would stick with the same RPM. now, if you doubled the HP/torque you would be in the same ballpark. I take it you have a motor you want to use?

Larry, a 1725 RPM motor will have twice the torque of a 3450 RPM motor of the same power rating, so the saw blade wouldn't know the difference if you used proper pulley ratios.............Regards, Rod.

[Larry Edgerton]

Cool. Wass going off of my racing experience with gas motors, not my electrical lack of knowledge.

So Fred, the Torque problem is not a problem.

[Mike Henderson]

The only significant difference is that the 1725 motor will probably be physically bigger. As Rod pointed out, the 1725 motor will have twice the torque as a 3450 motor in order to produce the same HP. And generally, the motor will have to be physically larger to produce that double torque.

Otherwise, everything is the same. If you use a pulley to run the blade as the same RPM, you will have the same torque (and HP) at the cutting edge.

Mike

[In electric motors, HP is torque times RPM times a constant. Since a 1725 motor has twice the torque as a 3450 motor, when you use a pulley to keep the blade at the same RPM you will decrease the torque by 1/2 but double the RPM. The result is the same HP at the cutting edge.]

[Darcy Warner]

The slower the motor, the more poles and more windings, hence the bigger size

[David L Morse]

The slower the motor, the more poles and more windings, hence the bigger size

Except, each winding has fewer turns in proportion to the number of poles so the total number of turns doesn't change, just the way they're distributed. There's nothing about the physics of the situation that dictates a larger size for more poles. The torque multiple comes from higher current in the rotor bars, not from a difference in geometry.