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Thread: Electric Motor Question

  1. #1
    Join Date
    Jun 2007
    Oceanside, So. Calif. 5 mi. to the ocean

    Electric Motor Question


    A few weeks ago I posted about a Porter Cable dry grinder giving problems. Reports I have seen say $45 - $55 to replace the electronics. That is approximately 1/2 of the original cost; it is not a practical solution as far as I am concerned.

    The new PC variable speed dry grinder ran long enough for Glenn and me to put on new wheels, balance and align them. Then it started blowing fuses. Unfortunately I had left it in the box until the warranty was no good.

    What would happen if I just took the pig tail wires and hooked them directly to the motor through the switch and said, "To heck with the variable speed?"

    I assume that the motor will run 3,000+ rpm (yes I know what ASSUME stands for; that is why I am asking for confirmation or any other ideas). I would prefer the 1700+ speed. However 3000+ is better than nothing.

    Thanks and Enjoy,

    If pics would help, I will photo any part you wish to see.
    First of all you have to be smarter than the machine.

  2. #2
    Join Date
    Nov 2006
    Austin, Texas
    As an electrical engineer I know the theory behind the motors but am largely useless with the practical answers.

    But since I know nothing, that has never stopped me. The normal speed is largely dependent on the internal magnetic poles - so if the variable speed was up to 3500 rpm, I bet you will get that higher speed without the controls. If the variable speed was up to 1725 rpm, I bet that will be the speed without controls.
    Charlie Plesums, Austin Texas
    (Retired early to become a custom furnituremaker)
    Lots of my free advice at

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