Quote Originally Posted by Goemon View Post
That's different to what I was told and what the various sellers claim. Most of what I read said that a drive made for 1ph in 3ph out can be used to run spindles with the same power rating (I.e. a 5.5kw drive for a 5.5kw spindle) but drives made for 3ph in have to be derated by 1.7 or 2 (depending who you ask).

For example, this vendor offers both options with a significant price difference (a 7.5kw 3ph input VFD is far cheaper than the same VFD with 1ph in / 3ph out):

7.5 hp VFD, Single Phase to Three Phase VFD | GoHz.com

If you look in the reviews, there are some questions that are answered by the seller who states "there is no need to derate" (for their 1ph drives) and he goes on to give some explanation on why this is the case.

Aside from that, and more importantly, I also read that the most important thing is to match the input and output amps / current with what you can supply (from your outlet) and what your spindle needs to operate. These numbers were quite different on the 3ph in drives to the 1ph drives I looked at.

Now, VFDs are not my area of expertise. You could be right for all I know. Just because you are the only one saying something doesn't make you wrong - espiecially with anything CNC related where nobody seems to agree on anything. I see lots of posts with people regurgitating info I know for a fact to be wrong. I just have no real way of knowing who are the actual experts who have kept their knowledge current vs people who regurgitate info that was never right or hasn't been right for 20 years.

If 3ph 7.5kw VFDs can be used to run 7.5kw spindles from a 1ph outlet with no derating needed, that is useful info that should be out there so people can stop regurgitating innacurate info.
There is a derating the minute you use single phase, If anyone is saying there is not, they are talking Bs, there is no difference in there VFD Drives as to any others, they just want you to buy the more expensive single phase VFD Drive, most have the same R S T input terminals for 3 Phase connection, you are paying the extra for the label ( Single Phase )

Your motor spec's are suspect as well, if it is 5.6Kw @ 220v this would be 25.4amps I have not seen you mention 25.4amps anywhere