Buying OBM grinder - what motor and VFD to get

Feezle

Feezle

Joined
Jan 30, 2012
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519
I think I have settled on the OBM grinder. I am mechanically and electrically illiterate and I wish there was an option to have the thing wired and ready to go but there isn't. So I'm going to need a motor and VFD. Correct me if I'm wrong but the set that he sells for $575 doesn't appear to be that great of a price. I don't have a 220 line so i have limitations and I'm just looking for a decent reliable motor and VFD to get me up and running.

Do you guys have any recommendations? I have found some older ones but the links typically lead to items that are long sold out.
 
Well, while 3hp is nice and surely don't hurt a thing at all. BUT - you will need 220vac for sure on that. If you really only have 120vac, you might look at a 2 hp motor: https://goo.gl/NmJi7D it would run on 120 vac, you just wouldn't have full power, which you'd never really notice anyway except for heavy hogging. For the VFD, the best of best with money as no object would be the nice KBAC-29 1P listed by Marc. BUT - if money is a concern (as it is for me) many folks are using a Chinese VFD that will handle up to 3 hp, and sells for $110 or so shipped. They are NEMA 1 enclosure so you'll need to rig up a filter over the air inlet, or mount in a dust proof box.

Oh, there is also this 1-1/2 hp motor: https://goo.gl/XhH1aL for $142 shipped.

Ken H>
 
Ken H> said:
Well, while 3hp is nice and surely don't hurt a thing at all. BUT - you will need 220vac for sure on that. If you really only have 120vac, you might look at a 2 hp motor: https://goo.gl/NmJi7D it would run on 120 vac, you just wouldn't have full power, which you'd never really notice anyway except for heavy hogging. For the VFD, the best of best with money as no object would be the nice KBAC-29 1P listed by Marc. BUT - if money is a concern (as it is for me) many folks are using a Chinese VFD that will handle up to 3 hp, and sells for $110 or so shipped. They are NEMA 1 enclosure so you'll need to rig up a filter over the air inlet, or mount in a dust proof box.

Oh, there is also this 1-1/2 hp motor: https://goo.gl/XhH1aL for $142 shipped.

Ken H>
Click to expand...


Dang missed the don't have 220....
 
OBM is listing the smallest model of VFD's....Mod24...Mod27....Mod29....
Model 24 is for a 1hp 3phase motor that when powered by 110v will Net only 3/4 hp.
Model 27 is for 2hp 3phase motors and when powered by 110v will Net 1-1/2hp
Model 29 is for 3 hp.
As you can see there is a loss of Net horsepower when wired to a 110v supply and it doesn't matter which brand of VFD you use.
The point being if you base your purchase off just the price you are limiting your applied power to do work 1 hp or less is brutal and slow you won't be happy with performance. A 2hp motor delivering 1-1/2hp off 110v is a very popular option since if the option to up the voltage to 220v in the future will NET the original full 2HP with the existing motor....I'm currently running 3 grinders with 2hp motors off 1 KBAC-27D....If you have to save a little more $ to make the up grade to 2hp motor that is your best option.
 
That helps quite a bit. I was pretty sure that setup would be underpowered.
 
Only if you have 220. See the motor rating.

Leeson 116747.00 general purpose ENERGY EFFICIENT AC Motor:
Specs:
2HP
1740RPM
56C
TEFC
230/460V
3PH
60HZ
CONT.NOT.40C.1.25SF.
RIGID C
GENERAL PURPOSE
C6T17FK97C
WATTSAVER.AUTOMATIC
 
Yes, that will work. The VFD is going to take the 120 input and change it to 240. You'll use the jumpers in the VFD to set it up for 1.5HP and single phase 120 in and three phase 240 out.
 
Agreed that combo will work...I think you can shop around for a better price. Items may come from 2 different vendors but if you save $100 you can use it for the Wire and Plugs you will need.
 
I saved $30 making an offer. I'm also getting cashback on my credit card and double fuel perks getting gift cards for ebay from my local grocery store, so I think I'll stick with this one. Thanks for the links though!
 
Is there an idiot's guide to wiring one of these up somewhere? I need to know what all else I need to get it done.
 
There will be a wiring diagram with the VFD and with the motor. You'll need to check the motor and possibly change wires under the cover so it's set up for 240v. It's not complicated, the diagram is usually pretty good.

The VFD may be a little more complicated but they're all slightly different and the manual is the best thing to follow. You'll have questions like "where does the ground go?" or "What is L1 and L2?" or whatever but those are easier to answer when you have it in your hands.

Unless one of the guys with that VFD can chime in, I would say just wait until you get it and when you do, be ready to post pictures of the terminals you have questions about, if you can't figure something out with the manual.
 
I'll do that. What will I need in terms of wiring? I'm assuming there is a wiring kit I can buy so I have it ready when it comes?
 
Eh, there might be? You'll need a 20 amp breaker in your panel, 12/2 wire from there to the VFD. That will attach with screw clamps in the VFD. Then you'll need 12/3 to go from the VFD to the motor, which you will either hook to the motor with crimp on terminals or wire nuts if there's an existing pig tail. A compression fitting here or there, at lease one for the entry to the box on the motor.
 
kuraki said:
Then you'll need 12/3 to go from the VFD to the motor
Click to expand...
Note, that 12/3 actually should have 4 wires - 3 hots (1 wire for each phase) and a ground wire. #14 for that short run will work just fine also. A 2 hp 3 ph motor at full load is only around 7 amps, and #14 is rated for 15 amps. From the VFD to 120vac recept outlet you'll need #12, or even #10 wouldn't hurt, depending on how long the cord is.
 
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