3 Phase Motors running on single phase 2

[ElChispa]

I need to change 2 pool pump motors running on 3 phase to single phase. they are 240/380 volt running at 2850 rpm. I know it can be done using 2 capacitors, but how do you calculate the size of the capacitors?

 

[burnt2x]

Insufficient data! No solution!

 

[ScottyUK]

You need more than two capcitors. Easiest way is to use a small inverter. They are dirt cheap these days.


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If we learn from our mistakes I'm getting a great education!

 

[stevenal]

Or a variable frequency drive suitable for single phase supply.

 

[Skogsgurra]

???

Is there a difference?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[stevenal]

Yes,

An inverter is a component of a VFD.

http://en.wikipedia.org/wiki/Inverter_(electrical)

 

[Skogsgurra]

Hmm..

There may be some dispute about that. I am sure Scotty meant a complete VFD. Free-standing inverters for motors are not very common or practical. Nor are they dirt cheap.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

ElChispa
About the only answer you will get on this site is to use a Variable Frequency Drive suitable for a single phase input.
It is possible to run three phase motors on single phase with capacitors. If your pumps are closely matched to your motor sizes you may have problems getting full output from the motors. If the currents are not balanced, the motor will generate more heat. This extra heat from unbalance will limit the maximum load that the motor can pull.
If you are determined to use three phase motors on single phase, try the Do It Yourself forums and/or hobby forums. There you will find people with hands on experience with running three phase motors on single phase with capacitors.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Cheap.

Example:

http://www.factorymation.com/s.nl;j...e3eSbNqNc38Le34Pa38Ta38Naxz0?sc=2&category=11

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hey, I like that, Keith.
I didn't realize just how cheap VFDs were getting.
Thanks

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Skogs,

Yes, you know what I mean.

Stevenal,

You are right too. The two terms are (incorrectly) used pretty much interchangeably in colloquial discussion among people who use / install / repair them. I would be more careful in a written specification. Is it different in the US?


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If we learn from our mistakes I'm getting a great education!

 

[stevenal]

Not sure I can speak for the entire US, but I have not heard one called the other before. In my field inverters are used to connect PV systems to the grid and to power tools from vehicles.

 

[ScottyUK]

If someone said "I'm going to run that motor from an inverter" I'd normally expect he meant from a VFD, but I take your point: if someone said "I'm going to connect that PV array to a VSD" I would be givig him a very puzzled look.

'Twas careless on my part - I will pay more attention in future.



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If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

Scotty; I have many times heard people refer to VFDs as 'inverters'. Heck I used to refer to them thusly until I became more ordered here in E.T.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

I did a paper on this a long time ago.

Inverters came first as a general technology in the mid '60s, AC Drives that used inverters in them came much later. Here in the US, one of the first commercially available PWM drives was the "Parajust", made by Parametrics and they actually copyrighted the term Adjustable Frequency Drive (AFD). Subsequent competitors used the term Variable Frequency Drives (VFDs) from the outset because of our penchant for TLAs. Later when the Japanese (Yaskawa, Toshiba, Mitsubishi) entered the VFD market big time in the mid '80s, they had marketing departments who translated their Japanese marketing materials directly to English rather than hire US marketing professionals. Because of the language differences, TLAs meant nothing to them so they put out marketing campaigns that called them "Inverter Drives" (as opposed to mechanical drives I suppose) since that is what their Japanese terminology translated to best. Since they became dominant very quickly and are largely responsible for the explosion in use and acceptance, the terminology stuck with us as an industry, but we (being largely a linguistically lazy lot) just shortened it to "Inverters".

I gave up correcting people years ago though. I was accused of being pedantic and really, we all know what we are talking about by context anyway don't we?

 

[Skogsgurra]

Right Jeff! And Amen!

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ElChispa]

Thank you all for your content. I can confirm that bill is right, you can convert 3 phase to single phase using capacitors, last year, a friend ordered a single phase motor which when it arrived proved to be a 3phase converted with 2 capacitors of differing sizes. For the installation in question, a VFD becomes expensive against capacitors. However, the information I have obtained from ABB motors do say it is possible, but not reccomended due to the slot geometry being different in 3 phase and single phase motors. This means you can probably double the current drain to run in single phase.

Many thanks

Ernest

 

[itsmoked]

That and I don't believe you will get the motor's rated power from the capacitor shtick.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Most static phase converters need a number capacitors, at least one transformer, some sort of protection, some form of enclosure... like I said early on, 'more than two capacitors'. This lot will probably cost more than a cheap VSD (I'm paying attention now guys!) especially one bought from eBay where they frequently go for bargain prices, and will give poorer results.


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If we learn from our mistakes I'm getting a great education!