VFD question

javand

javand

Joined
Oct 17, 2010
Messages
2,424
Ok, so, admittedly, I'm new to knifemaking gear, and never used VFDs in general, so forgive me if this question ends up being dumb.


I'm planning to build a grinder, in fact I found a good deal on a 1.5hp 208+V 3-phase 56C framed Baldor motor on ebay last night, and it's already en route.


All the information I see regarding the use of VFDs concerns using a single phase 120V VFD input to 3-phase 230V 3-phase output.. Any reason I can't run a 240 single phase circuit to my shop and use something like this instead: http://cgi.ebay.com/VARIABLE-FREQUEN...t_13423wt_1141



It's much cheaper than any of the equivalent converting VFDs I've seen, and I'm capable running to infrastructure myself, although I'm not an electrician, so I understand I may be missing something fundamental here.

Any reason other than convenience people are using the 120 single to 240 3-phase VFDs? Don't you guys have 240 circuits in your shops and isn't it generally more efficient power consumption wise to use ?



Thanks guys, feel free to berate me and call me names if I deserve it.. ;)



Javan
 
Hey Javan...

Your link isn't working right now so I can't comment on that but...

The KBAC-27D VFD that I drive my 2hp KMG with will handle either 120V single-phase input OR 240V single-phase input and convert to variable frequency three-phase out. You can find a data sheet on it HERE. I run mine on a 240V circuit.

Erin
 
That one looks similar to my Teco FM50 203, which is a VFD that takes only +/- 220V, 1 or 3phase. Mine is a bit cheaper than many as well, such as the KBAC model that many use. The main price difference is not in the input voltage it will take, but in the enclosure rating. This one is definitely open and not highly protected against grit, dust, etc. in the environment. You can build a box for it, or mount it WELL away from your grinding operations, these measures help a lot. The more expensive ones many use are often NEMA 4 rated, meaning it keeps this stuff out. These can be mounted right on your grinder if you like.

I'm happy with my TECO, the way it's mounted, you should be able to protect this one as well. It looks like it would work, of course I can't vouch for the quality as I've no experience with the brand. It is the very cheapest 3hp VFD I've seen yet.
 
If thats what you want to buy then just run a 220v single phase line to your workshop and plug it in. It should work fine.
Personally I went with a 110v unit so I could move my grinder around anywhere in my shop. But the decision is yours and it should work fine.
PS Just noticed that this is a VFD for a three HP motor, and you have a 1.5hp motor. I would do more research to ensure you can run a VFD under its rated capacity without fear
of damage.
CW
 
remember, you need to upsize the VFD if doing a single to 3 phase conversion
for a 2 HP 208/3 ph motor the drive should be rated at least:
120 vac input : 208/120 x sqrt(3) x 2 HP ~ 6 HP
240 vac input : 208/240 x sqrt(3) x 2 HP ~ 3 HP
the math can be done in KW also

the single phase line current will be much higher than the 3 phase current for a given HP
 
Awesome guys, thanks for the reply.. I was just using the VFD in the link as an example, I tend to avoid the absolute bottom of the barrel, but I like to know my options.

I was absolutely unaware of the enclosure rating relevance, thank you Salem, definite food for thought.


I currently don't have any power in my shop, so running whatever I choose isn't an issue. I considered the up-sizing.




Awesome guys, I feel progressed.
 
You must log in or register to reply here.
Back
Top