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Old 02-08-2007, 07:00 PM
jbw jbw is offline
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AC or DC motors?

I own a fabrication shop and am making myself a grinder. I have a great understanding of steel and fabrication processes but dont know jack about electricity or what motors to use. Why do people use dc motors and why is the variable speed grinder needed. Can anyone help me out with this.
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Old 02-08-2007, 07:58 PM
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Ray Rogers Ray Rogers is offline
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Probably nearly everyone can help you out with this. DC motors are used because that is the cheapest way to get an electrically varied speed. It takes a really good DC motor and controller to make a decent grinder.

Variable speed is 'da bomb' . You can do the same thing with a few pulleys but once you've tried a variable speed rig you'll never go back. The finer the grit you use, the slower you'll want to go, generally speaking. This makes your expensive belts last longer and reduces the heat build up from fine grits. Variable speed can also give you more control on difficult grinds. Lots of makers have lots of reasons for using variable speed and they are ALL good....


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Old 02-14-2007, 01:44 PM
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Harry Mathews Harry Mathews is offline
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Underline every thing that Ray said from the word "Variable" right down to the last dot after "good...." and then put a star out beside it!


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Old 02-15-2007, 03:14 PM
SamLS SamLS is offline
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I think AC is the less expensive route. The DC motor alone 180v @ 2hp 1750 rpm is $600-$1500 surplus new. While the AC motor is $50-$200 surplus new. Both AC and DC drives can be had surplus new or reconditioned $100-$400.
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Old 02-15-2007, 09:53 PM
jbw jbw is offline
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Thanks for the post Sam i agree with you. AC motors are much less expensive and easier to find. I have a 2 hp AC baldor 3 phase motor all i need is a drive that has single phase input and 3 phase output. They make such a thing right? If im not mistaken kmg grinders have AC motors.
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