Hello,

I have a 220v 3 phase 8HP motor, the problem is my shop only has single phase 220v power. What is the best, and by best I mean cheapest, option to convert this power.

Thanks

 

The easiest is a phase convertor.
http://www1.mscdirect.com/cgi/NNSRI...re=ItemDetail-_-ResultListing-_-SearchResults

Here's one, shop around, Google them. There's also plans out there on how to build them. Since we don't know your skill level, well a off the shelf unit might be best for you.

 

Gerty,

thanks for the post. I was hoping to come up with a cheaper solution. Truth be told I am kind of a tight wad. Anyway, I am fairly skilled when it comes to mechanics and have a decent amount of knowledge when it come to electronics. Could you give me a quick overview of what it would take to build one of these so that I can decide if its over my head?

Thanks

 

The problem you are going to find is that any commercially available option is not going to be cheap for the power requirements you need. That is if you think $200 is expensive. Some of the better phase conveters are more expensive than that. As to the design and building of one your self... Well how reliable do you need it to be? Less expensive is sometimes really cheaper.

 

BSomer,

This is going on a piece of equipment that is going to be in operation here and there. Its not like its going to run everyday, or anything like that. That being said, when I start the motor, I want it to run every time I start it. Maybe the 200 bucks or so is worth it.

 

One of my personal rules is that I never design anything that can be purchased retail because the parts will cost me more than the product and the time I spend will not get me anywhere near "state of the art" performance. I just can't compete with manufacturers that have been honing their product for years.

 

If you can look at something and tell if it within you skill level to build, look at this link. It has a ton of RPC (rotary phase converter) plans, information and if you join, very helpful people.

http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/

 

Hello,

I have a 220v 3 phase 8HP motor, the problem is my shop only has single phase 220v power. What is the best, and by best I mean cheapest, option to convert this power.

Thanks

You've got one thing going fo you - you don't need to step up the voltage. If you did, I wouldn't be able to recommend this, but I can:

http://www.driveswarehouse.com/p-2124-pc1-75.aspx

It takes 220V single phase in and puts out 220V 3 phase 0-600Hz

You could save a considerable amount of money if you derate the motor and use a smaller VFD. Do you really need all 8 of those horsepower?

Shop around, there are several manufacturers of VFDs that accept single phase input, many of them much cheaper than the one I linked to, but I'll leave the tiring shopping up to you.

 

I appreciate all of you responses. I have done a lot of research on this subject of the last couple of days, and have decided to build my own static phase converter. I know this is a very basic question, but I want to cover all of my basis before I start looking into buying parts. The motor is a 20 amp motor, and the questions is, is the motor 20 amps per phase or total. I'm going to run the timer in the converter off of the 220v, I just don't know what size timer (current) to purchase.

 

"static" converters are very inefficient. A RPC is really the way to go.

 

It is not just that static is inefficient, it is really not a converter but more of a starter, you typically get at most 2/3 of the power of the motor, so if you need 8 hp upgrade your motor to 12 hp. I think the variable frequency drive is the way to go. Even using a free motor in a rotary phase converter gets expensive after you get the parts to start it and control it safely. And the vfd gives you motor speed control that you do not get with other solutions.

 

Been a couple of years since I bought my last VFD, but at that time they did not make one that they would warranty when used on single phase over 3 horse power. And for the 3HP they wanted you to buy a 5HP unit. This was a Teco brand VFD.

 

"static" converters are very inefficient. A RPC is really the way to go.

I'd say that used to be the case, but not anymore. Digital Signal Processing and micro-controllers allow for some amazingly efficient and capable phase converters these days. Check these out http://www.phaseperfect.com/ - not cheap but they will outperform RPCs any day of the week and give you utility grade or better power at performance levels you won't find in a RPC.