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Alex Middleton

Worth it?

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I have an opportunity to get this old buffing stand free from work.

20190813_055739.jpg

She's 3 phase, 440 volts, 1750 rpm, and 2 HP.  I've been toying with the idea of upgrading my little 2x48 to a 2x72 but I don't have the nest egg built up quite high enough yet.  Obviously there would be quite a bit of fab work involved in changing this over but that is all pretty straightforward, and honestly quite a bit of fun.  With the dual spindles it actually opens up all kinds of possibilities in my head.

I'm more concerned with the electrical aspects of it as that is not something I've really ever played around with.  I only have 220 coming in to my shop.  I believe I can use a VFD to convert the 220v to 440v but I'm not sure?  Also, at 1750 RPM, would I be able to get the most out of high end belts during heavy grinding?  I know I could step up the RPM's to the grinder with a belt/pulley to get it up around 3500, but wouldn't that cut my HP in half?  And if that's the case, would it really be worth all of the trouble?  Sorry for all of the questions, but there is a narrow window to be able to grab this thing and I want to make sure that I'm not just going to be wasting time and energy.

Thanks,

Alex

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You can certainly run that with a VFD that would plug into your 220 single phase.

A VFD will indeed allow you to bump up the motor speed, but your shouldn't try to double it.  The rotor (the spinny-bit) of the motor may not be designed, or balanced to go at twice it's rated speed.  If it did hold together, you would reduce the torque significantly, so it wouldn't benefit you much if at all.

A 6" drive wheel would get you around 2700 feet/min of belt speed at 1750rpm.  That is on the low end for really hogging off material, but I do a lot of my detail and finish grinding at much less than full speed on my grinder.

If you don't mind doing the fabrication work, I think you would find that a significant upgrade to a 2x48, but it won't shred material off like the grinders that run at 6k feet/min or more.

 

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Brian, thank you for the confirmation on the VFD.  That was definitely my biggest sticking point on whether or not to go for it.  I honestly didn't even consider that I would be able to go over the 1750rpm on the motor with the VFD.  That just seems like a bad idea for all of the reasons that you mentioned.  I was thinking about linking the motor to the grinder with a belt and having a smaller pulley on the grinder.

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It's free and you haven't taken it home yet?

The motor may be able to be wired internally to 220VAC  3 phase then no problem running it with a VFD and your  220VAC shop voltage.  It should be marked with required voltage(s) on the motor spec plate.

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The motor is marked as 440v, 3-phase.  I think I'm going to grab it if it's still available.   Worst case I can sell/scrap it at some point in the future.

Edited by Alex Middleton

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If nothing else,the stand is probably worth taking home.  If the motor runs and the bearings are usable, then a VFD and some pretty simple fab and you've got a belt grinder.  You could upt a circular disk on one side, or just run a stone for when you need that.  It's a pretty cool find.

Just my .02, but I'd snatch it up if I were in your place

 

Geoff

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Thanks for the help guys.  It's got my name on it and I'm bringing it home on Friday.  It'll make a great project for this winter.

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Ok, lets just say that when it comes to any electrical wiring outside of a basic household switch/plug, I'm about as good as tits on a boar hog.  Just never had any exposure to it.  I've been searching around the internet this morning trying to find a VFD that will go from 220v 1 phase to 440v 3 phase without any luck.  Does anybody know of one that's commercially available?

I've only been able to come up with a couple of options:

 1. Install a rpc to convert my 220v 1p to 220v 3p, transform from 220v 3p to 440v 3p, then add a VFD or step pulleys for speed control.  The upside is that I'll have 220v 1p, 220v 3p, and 440v 3p already in the shop and available for future use.  The downside is obviously the expense.

2. Use a VFD to do my phase conversion at 220v, then transform up to 440v.  This one is obviously the cheaper/easier route but I don't know if having the transformer after the VFD will work.  Also, it seems like it might be pretty much dedicated to just the one piece of equipment.

3. Use the same VFD to go from 220v 1p to 220v 3p and then just spend the $200 and buy a brand new 2hp 3450rpm TEFC motor. (I think I'm starting to lean toward this option.)

Thoughts?

Edited by Alex Middleton

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I would have bet my vfd could run a 440v motor, but now you have me questioning that.  Wayne sell the same drive I use, and he'll know for sure.

I can eliminate your option #2.  You can't really have a transformer between the VFD and the motor.

It is quite possible the motor can be reconfigured for 220v.  Many 3-phase motors have options for running both high and low voltage depending on how you connect the lead wires.  If this is the case, it will have a diagram inside the box where the connections are made.

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I'll have a buddy of mine look at the motor once I get it home and clean it up a bit.  The guy is a genius with all things that make sparks.  I'd really like to utilize this thing if possible.  I have an idea in my head of mounting a 2x72 on one side and attaching a collet chuck to the other.  Then I can mount stone wheels, buffing wheels, disc grinder attachment, etc. on arbors and create a sort of quick change system that will allow me to easily switch from one to another.  It all sounds good in my head, whether or not it will actually work is another question entirely. :D

On a separate note I did stumble across a 2hp VFD that will take 115v 1p and output 230v 3p.  It's a little bit pricey at $300, but probably cheaper in the long run than wiring up a 220v outlet and still buying a VFD on top of that.  If I end up purchasing a new 220v 3p motor I may just go that route.

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Yeah, 2hp is about all you can pull out of a standard 115v outlet.  Think of the power like the volume of our steel while we forge it.  We can change the shape of the steel, but can't add any volume.  The VFD can change the shape of the power, but it can't add any.  All you are ever going to have to work with has to come out of the outlet.

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Beware that 2hp 115v motors generally require a 20amp circuit, which is not standard. The standard is 15amp. So you may have to upgrade your circuit either way.

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