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variable Speed DC motor question

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  • variable Speed DC motor question

    I picked up a Grove Gear 100:1 gearbox attached to a Magnetek variable speed DC motor yesterday at an auction.

    I have a ring roller project that I'm going to use the gear box on.

    I don't know a thing about this type of motor, and would appreciate any input you can give me.

    It's listed as 1/4 HP, 1725 RPM, I've done some searching on-line, but can't find the voltage/amp requirements. Any ideas?

    Does anyone have a recommendation on a power supply to run this?

    I hooked it up to a 12v 12a battery charger and the motor/gearbox works, just no where near 1725 RPM ( at the motor)..

    I can get an AC motor with the same frame as this one that will work on the gear box, but I'd like to use this DC motor if possible.

    ideas or questions?


    Last edited by 67chevelle; 02-24-2008, 07:04 PM.

  • #2
    What is the voltage rating? Surplus Center has DC speed controllers that are quite reasonable. We use these- they're kind of pricey for HSM though. could get one from a junk treadmill.


    • #3
      The voltage should be on the label attached to the motor. Most of these are in the range of 90-130VDC. If you got the motor to turn at all on 12v, I'm guessing it's a 90v motor. As Rustybolt already said, controlers are available at a reasonable cost. A controler will give you variable speed with little loss in torque.


      • #4
        Good guess CCWKen..

        I looked over the label on the motor twice and didn't recognize any of the numbers as voltage or amperage requirements. Upon closer inspection,

        V arm 90
        A arm 2.9

        Must mean 90 volts, 2.9 amps..

        Normally I'm not this obtuse, I was looking for something that looked like the fields on the plates for AC motors.

        Can I use something like this?

        Or do I need something that matches exactly?




        • #5
          Yeah, that will drive it....its a bare bones drive. You'll have to add a potentiometer to it to get the variable speed,-- notice that it says that it wont start at speed, you have to back off the pot to near, or at, zero (the better controllers dont require this)

          I have doubts that 1/4 hp will come close to handling a roller....
          If everything seems to be going well, you have obviously overlooked something........


          • #6
            I think 1/4hp should handle it. Don't forget, the box is 100:1. I'm running a 1/5hp through a 100:1 box on my bead roller. It's got 1.5:1 drop by chain drive too so it's not lacking power. I'd like to drop the speed even more. The off on start up isn't such a bad idea for many applications. Mine included. I put the rheostat in a foot pedal. So when I raise my toes, it goes to zero.

            The controller in your link is 130v. That won't do a 90v motor any good. That's almost 45% over voltage. Changing the rheostat doesn't change the applied voltage. It simply changes the time it's applied. I'd look for a 90v controller.


            • #7

              I appreciate the input and guidance.