ECN Forum Forums General Topics of the Trade General Discussion Area Phase Inverter/converter question

A customer of mine has a custom wood working shop at his house. I wired the shop two years ago and it has a 200A 1ph service.

He is purchasing a new moulding machine and vac system that that requires 3ph. The motors will draw a total of 142A @ 240V/3ph.

Having 3ph power from the poco is inot an option. He is miles from any three phase primaries

I have never converted 1ph to 3ph and was wondering how this conversion effects amperage on the primary. Will the draw be greater on the primary or will the secondary equal the primary.

Any one with any formulas for me?

It looks like your going to be doing a service change. If the motors draw that much there is no way your 200 amp service is going to be able to supply enough power for the required size rotary phase converter. I'm guessing you will need at least 300 - 350 amps single phase just for this equipment. Do a search on Google for "rotary phase converters" and you should be able to find some sizing info.

Curt

Just as caselec suggested, converting single phase to three phase with a converter doesnt relieve the primary at all. The load is pretty much the same.
John

[This message has been edited by scjohn (edited 10-11-2002).]

To add some information here, the complete picture - Power Suplying System and Load Device - will have a fixed KVA level. The load draws "X" amount of KVA and the supply must be able to deliver at least the same "X" KVA level, or the load will not be able to draw the required True Power (Wattage) it needs to develope the required Horsepower and Torque.
Results are a decrease in Rotor speed when the work exceeds the maximum HP which the Motor can develope.
This causes most Induction Motors to stall when they slip too far behind or come within a Syncronous Frequency point.

So much for the boring babble!

I ran some numbers and here are the results:

<OL TYPE=1>

[*]Using the listed 142 Amp @ 240 VAC 3 Phase figure, this equals 58.96 KVA - 58,958.4 VA to be exact,

[*]58.96 KVA on the Single Phase side relates to 245.83 Amps @ 240 VAC 1 Phase.
</OL>

Just something to consider.

P.S. here's the formulas used:

KVA:

I x E / 1000 [1 ph.] I x E x 1.73 / 1000 [3 ph.]

Amperes:

KVA x 1000 / E [1 ph.] KVA x 1000 / 1.73 x E

Scott S.E.T.

Scott35, Thanks. I went to my ugly book to work it out but couldn't figure out how to convert back on the line side of the converter...???? (I think I confused myself there!)

I'll have to get more info from the manufacturer on this machine. The only specs I have got is the 100 amp requirement on the moulder and a 15hp vac system.

Scott35 - I agree with your math but a phase coverter is not 100% efficient.

Arseegee - try this link http://www.phaseconverter.com/rotary-converter.sizing/

Caselec, that's what I was thinking. Thanks for the link too!

To add a note, this machine has 4 motors on it. A 2hp, 7.5hp, 10hp & 15hp. All drive different spindles. Then the dust system has another 15hp motor on it.

Guess it's gonna be a service upgrade. But who could have dreamed of a $35K planer/moulder at someones house.

Online application info at sites like: http://www.gwm4-3phase.com/appguide.htm

Also, don't forget NEC Article 455.

Dohh.. didnt do the math. The load isnt "pretty much the same".
Sorry for the hasty inacurate post.
John

Um, that is going to be one whacking great converter. something to suggest would (wood? ) be to replace or spec the motors to be single phase. Then you are looking at "just a service upgrade" rather than also adding a converter. Your probably into rotary converters to get any kind of efficency out of it, great amount of floor space, and noise too. the noise of the converter probably isn't an issue because a 3 spindle moulder can be heard several counties over anyway.

Just a thought.

Trainwire