I was on ebay and found this way of makinf a phase convertor

[chris heinis]

Moderator removed direct link to eBay - TOS Violation - do an eBay search if interested.
Ken Salisbury

Is this crap or does it work? If it works why aren't more people doing it. For my application I would need a 15 KVA transformer. I figure that it may be hard to come by. Any advice would be appreciated

[Noah Katz]

I don't know what it was, but all you need to start and run a 3-ph motor is pushbutton switch and a motor starting capacitor.

Google (I'd start with "home made phase converter") and you should find lots of info.

[Rob Russell]

I don't know what it was, but all you need to start and run a 3-ph motor is pushbutton switch and a motor starting capacitor.

That's true for a small motor and as long as you're OK with about 50% of the motor's rated power.

[chris heinis]

300046378879

I guess direct links are out. Here is the item number. I know there are static as well as rotey convertors this is a different design. I found it interesting. I don't know if it's a new way or not

[Mike Henderson]

Three phase power has been around a long time. I doubt if anyone has come up with some really new technique for generating 3 phase from 1 phase. Could be, but they'd have to convince me first before I put up any money.

I'd search the Internet and read the articles on that subject first. In general, all of the techniques are somewhat expensive and have certain limitations. For example, the lowest cost technique does not really generate 3 phase (but will run the motor) and you don't get full power from the motor. Also, you have losses in the conversion so the total power consumed will be greater than the power consumed by the motor.

Of course, even if it's not a new technique, the detailed instruction would be worth something.

Mike

[Rob Russell]

Without knowing what he's doing, it's a little hard to say ...

[chris heinis]

Did you check out his website. He has a crude video where he explains some things and a bunch of wires and caps all over a bench hooked up to the 5hp compressor motor
chris

[Robert Mickley]

He also talks about starting that compressor with 120 PSI in the tank
Guess he doens't know that compressors have an unloading valve so it doesn't start against the pressure.

[martyphee]

Looks like a scam. A 15kva transformer, even used, is going to set you back some bucks unless you find a deal. Also, a single phase one is about 150#'s. Three phase would be over 200#'s.

A static converter can be made for less than $100. Not some cheap crap that they sell on ebay, but a good one.

I built one for about $50 worth of parts. If you have a local surplus electronics store you can get the parts cheap.

I've found the best way for a big motor rotary or static is to use a time delay elay ($10 on ebay) to switch out the start caps. Probably one of the more expensive parts is the main relay, which will need to handle about 50amps. The static ones I've seen (recently bought) use potential relay's (used on frig's) I've found that they don't work well on large motor's. I haven't tried them on smaller motors. I used a static on my 18" delta planer. I first built one using a design I found that used a potential relay. It worked for a little while and then wouldn't kick the motor over anymore. I went to a rotary then. Recently I just sold the planer and had bought a static convert rated for 8HP off of ebay from Phoenix Phase Converter (250038000966) to go with it (thought I'd get more if it ran off single phase). It couldn't even turn the motor. The cap was 1/2 the MF it should have been and it used a cheap potential relay. I wanted to keep mine to use in a new rotary I'm building. Unfortuantly I had to give the buyer mine to go with the planer. Mine would start it up in less than a second.

A static converter will give you 2/3'd rated power.

[chris heinis]

I know he mentions the compressor starting with 125PSI. His compressor unloader is working to you can hear it blow when the motor stops. I just figured he didn't understand that aspect. He says it uses less energy to operate a nonmechanical tranformer than a rotary which is why he recomends the 15 kva transformer. I wonder how it works? Ust the two lines from the single phase and run power up the transformer separately for the third leg? What do you guys think. He won't tell you unless you buy his method
chris

[martyphee]

I believe a transformer will cause a leg to be 90deg out, but power is power. It's being used somewhere. Transformers aren't 100% efficient. You loss power as heat. Using capacitors makes a much smaller unit.

A well balanced rotary only draws a few amps without a load. I think my friend's 15hp draws 4 or 5 amps without a load. Mine would draw 8amps, but mine used a transformer to boost the power to 440v. The rotary is only there to generate the third leg.

Does the slave motor draw more as the load motor's draw more? I never measured everything with loads.

[chris heinis]

Well I guess it's a rotary then. Some say an air compressor is a hard start. Is that true if it has an unloader. What's hard to start oving the crank and flywheel?

[Mike Henderson]

How big is the motor you're trying to supply power for? If it's 3Hp or less, you'd do better to just buy a single phase motor - you can find them on eBay for decent prices. I bought a 2HP TEFC motor on EBay for about $125 shipped.

Even a 5HP might be better as a single phase than messing with a converter.

Mike

[martyphee]

Well I guess it's a rotary then. Some say an air compressor is a hard start. Is that true if it has an unloader. What's hard to start oving the crank and flywheel?

Your trying to run a compressor? Don't even think of using a static converter. You'll loose too much HP and the motor probably wont' be able to start. I wouldn't even consider a rotary unless your going to be using other tools because if the compressor needs to charge up the tank you have to go start the rotary and then start the compressor. Obviously you could put a start circuit in, but do you want to go through that trouble?

I would change out the motor with a single phase motor. You can get them off ebay cheap for compressors.

I would also be cautious about buying a used compressor unless you know the history. Was the oil ever changed? Was the air cleaner changes? How often was it drained... yada yada.

[Noah Katz]

"That's true for a small motor and as long as you're OK with about 50% of the motor's rated power."

Depends on what you mean by big; I made a rotary converter with a 7 1/2 HP motor and it starts lickity split.

I sold that and now I use AC drives I got from ebay. AFAIK most every one works with 1-ph input, with a 1/3 to 1/2 derating.

In a way it's not a lot different than a static converter. They have capacitors inside which are rated at only so many starts per hour, just like motor caps, but if you oversize the drive enough you'll get full motor power, and speed control as well of course.