# Static phase converters



## acro (May 3, 2011)

Need a phase converter for a 3hp milling machine in my home shop.

Milling machine is already variable speed, so i am ruling out a phase converting vfd as un neccesary. I believe I want a static phase converter for simplicity and cost. 

Question is, which one? They range from $100 to $300.

Few different brands on ebay, several saying usa made. I am going with a 3-5 hp range model for my 3hp 220v motor.

Anybody have any hands on experience with any of them? Maybe thw Phase A Matic

Thanks.


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## telsa (May 22, 2015)

Tubalcain went with a Red Chinese VFD of low cost.

It was ultra quick to patch in.

Go to his utube to see just how sweet it was. They take up NO SPACE. 

As for price, they are right down there in the gutter.

I'd contact the players that have and use lathes and mills... not us.


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## acro (May 3, 2011)

I am familiar with Tubalcain.



Thanks


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## 460 Delta (May 9, 2018)

Static converters are nothing more than a voltage sensitive relay and a couple electrolytic start capacitors. After the start, the motor is single phased, causing it to run hot and imbalanced[vibrate]. A better and cheaper solution is a RPC made from a salvage motor and some oil filled run capacitors. Iv'e made a few RPC's from salvage and they have run flawlessly and most important, they were cheap because they were built out of cast offs.
There is nothing difficult or esoteric in the build of these things, you just need a good junk pile I suppose. If you are a home machinist, you'll have a salvage pile.


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## Southeast Power (Jan 18, 2009)

This guy isnt an electrician but did a nice job explaining exactly how to build a Rotary Phase Convert.






Just be aware at the 1:55 mark, you are going to see a lovely thumb nail while holding a capacitor. It will be somewhat confusing for about a minute or so. :smile:


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## CoolWill (Jan 5, 2019)

I've bought and installed the North America rotary converters found on Ebay and other places. Oldest is 5 years and its still going strong. Avoid the static versions for the reasons listed.


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## gpop (May 14, 2018)

I have a ABB vfd in my shop that i used for a lathe. I liked the fact that the control panel could be mounted on the machine (simple Ethernet cable between the drive and vfd). Soft ramping was also a nice addition.


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## micromind (Aug 11, 2007)

I didn't watch the video so I don't know if this was included but if you're going to build a rotary phase converter, using a ∆ wound motor will give better results. 

Trouble is that ∆ motors under 15 HP are not very common.


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## acro (May 3, 2011)

My god. That fingernail. The rest of them look normal. Maybe he plays guitar, or has big nostrils.😲

And, using breakers for terminal strips. Lol. But you did say he's not an electrician.

I guess I don't fully get it. Static phase converters drop a phase on the motor and you have the associated issues.

With an RPC, you single phase a larger motor to feed 3 phase to the smaller motor. So, the smaller motor gets better power, but doesnt the larger motor on the rpc experience the same single phasing issues?


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## acro (May 3, 2011)

This guy does a very good job. Little long, but thorough. 

https://youtu.be/u229h7NcMxk


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## 460 Delta (May 9, 2018)

Yeah acro the idler motor is single phasing but it is mechanically unloaded. It's sole purpose is to help generate the missing phase, with the help of some capacitors. Unloaded with the caps in, it will be a little noisy and the manufactured phase voltage will be high, but loaded everything will calm right down.
If you only have the one machine, perhaps a VFD would be better, but the machine shop bug bites hard and you'll soon have a lathe and a shaper and a power hacksaw and a air compressor and on and on. A RPC of 71/2 or 10 HP or so will run a shop at home with ease.


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## acro (May 3, 2011)

So...

Somewhat theoretical, so bear with me. And I don't want to get too far into the weeds.

Assume we have 5hp pony motor, and 5hp mill/lathe/etc.

The incoming "2 phase" power runs the 5 hp pony motor to create the ghost phase. This incoming power is also parallel to 2/3 of the 5hp load motor.

If the 5hp load motor is fully loaded, the pony motor would be roughly 33% overloaded(thust the oversize recomendation). What load is on the input power? 10+hp?

While better power is supplied to the load motor, is the efficiency as bad as it seems?


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## 460 Delta (May 9, 2018)

The only load on the idler mechanically is bearing friction, so the power used for that is minimal. The power used from the single phase will be x 1.73 to = the three phase current. A 5 starting a 5 is doable but is difficult without a little cheating with a potential relay and start cap on the motor started. Yeah a RPC isn't a the most efficient way to make three phase from single, but it's rugged and easy to upgrade as the dumpster diving permits. If it uses a little extra power, hey coal miners need to work too!


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## acro (May 3, 2011)

Right on!


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## CoolWill (Jan 5, 2019)

Southeast Power said:


> This guy isnt an electrician but did a nice job explaining exactly how to build a Rotary Phase Convert.
> 
> https://youtu.be/GxpAoNCivPU
> 
> Just be aware at the 1:55 mark, you are going to see a lovely thumb nail while holding a capacitor. It will be somewhat confusing for about a minute or so. :smile:



He sounds like Napoleon Dynamite's brother.


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