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Subject: Electric motor guys??

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steveVa    Posted 04-26-2018 at 09:49:17 [URL] [DELETE]        [Reply] [No Email]  
  • Electric motor guys??
  • How do you vary the speed of a 2hp 115vac motor so that it will have good torque at low and high speeds? Thanks for any input.

    Philny    Posted 05-03-2018 at 19:14:57 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • You might want to look into a variable speed sheave

    Damon Lichtblau    Posted 04-27-2018 at 09:01:26 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • If it were me, I would find a suitable 3 phase motor and add a VFD. Single phase AC motors are going to lose too much torque when you take them under 60hz. The upside to going 3 phase with the motor is that the VFD will also do the phase conversion. (AKA single phase in -> 3 phase out).

    I have a bunch of old woodworking equipment that is 3 phase, and the VFD conversion works great. The only issue with running slow with this setup is motor cooling. The fans on older motors were designed to cool at full speed, so if you are running slow for longer periods, auxiliary cooling is needed.

    Peter MacInnis    Posted 04-27-2018 at 20:52:07 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • single phase motors are single speed only(yes there are some that are 2 speed but they run only one of them at a time). If you do slow down the motor, the start windings will cut back in, because of the internal switch, and the motor will burn out the start winding in no time flat.

    A 3 phase motor with "full vector" control can give good torque from 20hz to 70hz. That will cost a lot more than a few pulleys though.
    I am afraid the only way that is affordable is using pulleys. Sorry to bring bad news.

    Dave Smith    Posted 04-26-2018 at 19:13:47 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • What do you intend to drive with it?
    You're best bet might be to use a V belt with variable pulleys.
    When I was younger a friend used a small 3 speed transmission out
    of a foreign car to drive a band saw he built from scratch.
    Dave <*)))><

    steveVa    Posted 04-27-2018 at 08:10:36 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Electric motor guys??
  • Wood lathe. Trying to get way from the belt and pulleys. Speed is important when turning bowls. And my belt and pully set up takes several tries to get it right for different woods. There is a sp3ee controller for a router, but do not know if it will work on a lthe motor.

    Jack - Iowa    Posted 04-26-2018 at 15:11:33 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • I hesitate to offer this. IF the motor will stand it, a variable frequency drive might be the answer. Certainly would change it's speed and I don't think it would affect the torque appreciable. However running it slower would make it run hotter in my opinion.

    I'm no expert! You need to do lots of research.


    Island Mike    Posted 04-26-2018 at 10:32:38 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • I thought electric motors had a flat torque curve. That is they have maximum torque at low revs as well as high. However if there is enough horsepower, and you want something to spin faster than the motor's revs, then you need a gearbox. The gearbox will use a little of the motors power, so there will be a small reduction at the output shaft.
    Something to look up I think. I will do that later, to find out if I am anywhere near correct.

    One of my bikes makes 125 hp at the crank. By the time it goes thru the primary drive, then the gearbox and chain, and turns the back wheel, that has flex in the tyre: 108 hp at the dyno wheel. The new O ring chains have more drag than the older non O ring chains.

    Island Mike

    steveVa    Posted 04-26-2018 at 12:06:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Electric motor guys??
  • I believe that the torque is flat for DC motors with the proper variable speed controller, but AC motors are a different animal. Some AC controllers just vary the voltage and that would result in reduced torque.

    Island Mike    Posted 04-26-2018 at 21:25:50 [URL] [DELETE]        [Reply] [Email]  
  • Re: Electric motor guys??
  • Agreed I got my AC DC mixed up. BUT, an 18 volt electric drill can vary its speed, by varying the squeeze on the trigger. Must be rheostat controlled. I assume you can do the same with the AC motor. But I like the variably speed / gear box idea better. Of course an electrical genius might say we are all wrong.

    Island Mike

    steveVa    Posted 04-27-2018 at 10:16:57 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Electric motor guys??
  • You just reminded me that my grandpappy ran his lathe with a variable speed drill. But he was an electrical wizard who built his own variable speed for the drill. He also had a strobe that told him the speed when it made a spinning chuck look like it was standing still.

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