Some VFD's are designed to give full rated output power when connected to a single-phase supply and some need a three-phase supply to provide full output power. Read the spec sheets carefully. If it does not say that it will work with a single-phase input, it most likely won't.
VFDs that are only meant to be connected to a three-phase supply can still be used with a single-phase supply but you will only be able to get 57% of the rated output power, without risk of damaging it. Therefore, if you want to run a 2 hp motor from a three-phase input only VFD, you must use one that is rated at least 1.7 times larger than the rating of your motor, say 3.5 hp or greater. The larger VFD usually does not cost 1.7 times more. I am also seeing a trend towards more and more of the small (under 5 hp) VFD's being single-phase capable.
I strongly suggest mounting the VFD in a clean area well away from your grinder with on/off switches and a speed pot mounted in a handy location close your grinder. That is what the industrial users of VFDs typically do. It will probably only cost you another $20-40 or so for these extra parts. Metal dust getting on these parts should not make your VFD blow up unlike when it gets into the VFD itself. I believe that I have indicated suitable suppliers and their part numbers in some previous post. You will have to read the manual to see how this is done. The wiring to the switches and speed pot are typically all low voltage so there should be no danger to you. If you need help with this, send me an e-mail indicating the make and model of your VFD and where to download a copy of the manual.
If you insist on mounting your VFD where it will be exposed to metal dust, buy one of the ones that Rob Frink sells and save yourself a lot of heartache. These are about double the cost of one that is not dust/splash proof. I have never heard of anyone with a VFD, that was designed to be dust/splash proof, blowing up due to exposure metal dust. It takes a lot of R&D time to make a piece of electrical equipment dust/splash proof. I used to work at a company that made such drives but it has since been shut down by the new owners.
Please, please, please do not mount a VFD (or DC drive) that is not rated Nema4 or IP54 (dust/splash proof) near any source of metal dust such as your grinder. If you do, the metal dust will get inside and will cause a catastrophic failure of the VFD. Quite a few people on this forum have had that happen to them already. I know some people have gotten away with doing this for a while now but it is just a matter of time before their VFD blow up. Most manufacturers consider VFD's below about 5 hp to be disposable and are not set up to repair them. If the manufacturer does take it back on warranty, they will most likely notice the metal dust and will most likely void your warranty. In any event, the damage is typically so extensive that you will have to replace most of the guts. Contrary to what some people have said, you will not be able to get parts from Radio Shack to repair your VFD.
Stay safe and have fun.
Phil
by how motors are designated; frame sizes, face sizes, amperage ac and dc - this is all Greek to me. If I knew how to pose the query I'd go google this but I have no clue what to ask. Is there a chart somewhere explaining motor/frame/face sizes and the accompanying technical data? I don't want to, necessarily, get another grinder, just improve this one.
