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hoju1301
10-13-2006, 07:13 PM
Can I use a VFD that normally accepts 480V in and use 240v instead?

z28tt
10-18-2006, 09:51 AM
hoju1301 - Have you found any more info on this? I've seen many more 400V class inverters on Ebay, which would be an inexpensive way to get started. Are most 400V units strictly 3 phase input, and need to be derated appx 50% for single phase? Any units (sized 2-10 hp) that have phase loss monitoring that can't be disabled that we should stay away from?

hoju1301
10-18-2006, 07:17 PM
hoju1301 - Have you found any more info on this? I've seen many more 400V class inverters on Ebay, which would be an inexpensive way to get started. Are most 400V units strictly 3 phase input, and need to be derated appx 50% for single phase? Any units (sized 2-10 hp) that have phase loss monitoring that can't be disabled that we should stay away from?


yep. there are a ton of 400-500v vfd's on ebay that are cheaper than the 240v ones. i may end up buying one just to try it out. im probably in the same boat you are. the only snag right now is i need one that can do a high frequency (400hz) for a machine spindle.

what hp rating are you looking for? ac tech has a model with 5hp with a single phase 240v input. i got quoted around 400 for it and it has a ton of features.

there is also automation directs new line of vfds that are very competivly priced. current deration is i believe 1/3 if you use single phase but im not sure. a few have posted here using a 3ph vfd on single phase input.

ill let you know what i find out if i do end up buying one to try out.

z28tt
10-18-2006, 10:03 PM
I'm looking at the Hitachi SJ200's and L200's, as well as the Teco FM100's, or possibly a GS something from Automation Direct. They all seem to be about $200-$300. This is for a 2hp lathe motor... I'd be happy with "cheap and works" and give up the features for now, and treat it like a simple phase converter.

Andris

michaelvw
10-20-2006, 06:28 PM
Hello,

You can not use 230 V single fase for the input as the input should be 480 volts 3 fase. Don`t try it because it will not work.

Cheers,

Michael

unterhaus
10-20-2006, 11:22 PM
I don't think it will work, but really there isn't any reason why the manufacturer couldn't make it work. Just a matter of software. It would have to be a very crudely designed machine not to have problems.

michaelvw
10-21-2006, 02:13 AM
Hello,

Also don`t try 480 volts on a 240 volts VFD, I`ve seen VFD were this is tryed and the will explode. The capicitor in them will explode, at my work i`ve seen this because poeple use wrongly conected power source. Even a 240 volts models only conected to 1 fase and no neutral conected can lead to a explosing.

Michael

unterhaus
10-21-2006, 04:43 PM
high voltage caps are expensive, and nobody is ever going to design that much margin in. But putting in lower volts is safe.

JRaef
10-28-2006, 07:07 PM
Theoretically you can apply 240V to a 480V VFD, but why?

First off, you cannot go by HP, you can only go by current because a 240V motor is going to draw twice as much current as a 480V motor at the same HP. So if you compare prices based on current ratings, you will see that 480V drives are more expensive; they have more expensive components (only 10% or less of each transistor production run will pass muster for the peak voltages seen in 480V systems).

Secondly, since there really isn't such thing as 480V 1 phase power (except in some far flung farms), VFD manufacturers don't go to the expense of oversizing the capacitors for 1 phase operation, even on small HP drives as they do in 230V versions. Not only does that mean you must buy a VFD rated for twice the motor current, but since there is less margin for error, most 480V drives then need to have phase loss protection built-in in case a fuse blows and overloads the diode front-end. So if you supply 1 phase power, it will trip on phase loss. Some are available with that feature defeatable, some are not.

Third; most 480V drives have under-voltage protection set for -20% of the DC bus voltage based on their lowest input range of 380V. At 230V input the DC bus will not be high enough to satisfy that. Most VFDs do not allow you to defeat that feature.

Bottom line, even if you can get one cheap on eBay, the average seller will not be able to check these issues out for you, so you may end up buying a VFD that you cannot use. That makes them a lot more expensive!

lgalla
10-28-2006, 09:48 PM
Why not use a 240 to480 transformer?

JRaef
10-29-2006, 12:38 AM
That would work as long as the motor was 460V too. But most 460V motors can be connected for 230V, so the only reason would be what?

Again, why not just buy a 230V drive?

z28tt
10-29-2006, 11:26 AM
Again, why not just buy a 230V drive?

earlier...


I've seen many more 400V class inverters on Ebay, which would be an inexpensive way to get started.

After attempting to win something on Ebay for 2 weeks, I gave up and bought a Hitachi SJ200-015-NFU, so yes, I bought a 230V single phase drive. :)