Motor/ VFD Combo Help

A

adam britz

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Feb 16, 2017
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I was wondering what you all run on your grinding machines. My motor recently burnt up (repurposed from free treadmill) and it worked well, however, not bing enclosed, it shorted out. I am putting together plans for a motor/vfd combo and am a little confused.
It seems that the max HP motor/vfd combo I can run for 120v garage is 1.5. Is that correct? do you think 1 or 1.5 hp motor is sufficient?
Thanks for any help
 
Be better if you could get 220, but you can run a KBAC 24 off of 120 and use a 1 HP motor.
 
2hp 220v is my minimum. My future grinders will be 3hp and I'll re-purpose the 2hp motor/vfd to a grinder dedicated to small wheels.
 
I have 2 bader IIIs, 1 DC & 1 AC both variable 1.5 hp. The work well for me but I don't hog much.
 
1.5HP is plenty for most knife work. Production work and hard hogging needs more HP, but even 1HP works in most cases. I have grinders from 3/4HP to 3HP.

I used a 1.5HP DC Bader on 12oVAC for all my knives for over 10 years.
 
Last edited:
Stacy E. Apelt - Bladesmith said:
1.5HP is plenty for most knife work. Production work and hard hogging needs more HP, but even 1HP works in most cases. I have grinders from 3/4HP to 3HP.

I used a 1.5HP DC Bader for all my knives for over 10 years.
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What Stacy said! I currently have A 1 horse & KABC 24 120V on a mobile 2 x 72 for Demo & sharpening work and two others Grinders with 1 1/2hp motors in my shop. Years ago I found a few Non TEFC motors for cheap and used them with pulleys till I let the smoke out of two of them. The third I couldn’t kill. ———1 to 1 1/2 hp with 120 is fine unless you want to make 12” x 3” Bowie knives all day long! ——the other convenient thing about 120 is you can plug them in Anywhere!
 
1.5 HP is the most you'll get from 110VAC on a VFD. That said, I think you'll find 1.5hp (especially direct drive) plenty powerful for knife making. Can you bog it down? Sure, probably, but for most grinding applications, I don't think you'll notice a lack of power.

If budget is an issue, you can get into some open frame VFDs for quite a bit less than the KBAC units, but for more than 1HP, you'll have to step up to 220VAC. I think the KBAC drives ARE worth the investment however, and if you go with a KBAC 27, you can run a 1.5HP motor with a 110 input, and still have enough drive to upgrade to 2hp if you're able to get 220vac in the future.
 
i got a 3/4horse 6 pole motor 3 phase for 68$ new. Built a direct drive grinder with a freq drive running off 120V.
I have ground some big blades.
with a good drive you can double you hertz and double you rpm. that’s one reason my 3/4 6 pole works good because on 60hz it has a slower RPM but higher TQ. the freq drive over comes the 3 phase and low RPM.
That said if I were to build one I would say go with at least a 1.5 HP.
however with direct drive a drive and a lower HP motor setup correctly you can grind hard.
the drive has electronic in it that produce a better output then just 120 out the wall at 60 hz
 
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