Is it okay to over size a VFD

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Forum topic by ToddJB posted 12-27-2012 12:30 AM 2558 views 0 times favorited 5 replies Add to Favorites Watch
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8273 posts in 2308 days

12-27-2012 12:30 AM

If this specific question has been asked before I apologize, but I cannot seem to find a simple answer.

Does it harm anything if you oversize a vfd? Meaning if I have a 3ph 3/4 motor does it hurt anything to get a 1ph to 3ph vfd that is 1.5 hp… Or for the sake of argument a 10hp vfd? I know it does not work the other way around.

Any insight would be appreciated.

-- I came - I sawed - I over-built

5 replies so far

View wunderaa's profile


248 posts in 2380 days

#1 posted 12-27-2012 02:04 AM

Nope. Oversize as you please!

View TheCook's profile


39 posts in 2298 days

#2 posted 12-27-2012 02:10 AM

No problem at all. I’m using a 1.5hp VFD to run a .5hp motor in my shop.

View Grandpa's profile


3261 posts in 2853 days

#3 posted 12-27-2012 02:24 AM

I was looking into a VFD and the guy that was selling them on eBay said the motors had to be balanced and the same HP. I don’t have one and have never used one. I am just saying this fellow was saying you had to have the same. He said send him the spec’s and he would tell you if your motor would work. Like I said I have never used one and don’t own one. All I know is what I read about them. I would talk to Topomaxsurvivor before I used one. What he says will be straight. I am not disagreeing with these other guys so don’t jump on me. Topo will know since that was he business.

View exelectrician's profile


2328 posts in 2605 days

#4 posted 12-27-2012 04:34 AM

As long as the VFD has more HP than the motor you are good to go, with in reason, a 10 HP VFD driving a 1/2 HP motor will not get the current limit range you need and other hidden factors would make a mis-match like this reveal problems that would apply uniquely to every different make of VFD / motor combination.
With that said, as long as the VFD, HP is not more than two and a half times bigger than the motor HP, you should have reasonably good results.
Idealy they should match.

-- Love thy neighbour as thyself

View ToddJB's profile


8273 posts in 2308 days

#5 posted 12-27-2012 04:55 AM

Great news. I did’t want to keep upgrading my VFD if I ever decided to bump up my lathe motor size.

Thanks for the responses

-- I came - I sawed - I over-built

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