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#186912 06/03/09 10:04 PM
Joined: Jan 2004
Posts: 171
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Merlin Offline OP
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I have a customer that is wanting to convert some newer upgrades of a grain operation into 3 phase. Currently all that is available is a 400 amp single phase 120/240 service. Now in the past we have considered installing a 3 phase service but it has proven to be more costly considering this is a seasonal operation. Taking that into consideration, I believe that at this point, it is wiser to itstall a phase converter for the time being.

Can anyone give me some leads on some calculations to determine what I will need to install. I will be operating a 25HP, a 7.5HP and a 15HP, respectively at the same time. What I need to determine first is what the sigle phase load will be while these are running. There will be other single phase 240VAC loads running at the same time also but I am mainly concerned at what this new load will be.

Thanks
Kevin

Joined: Jan 2005
Posts: 5,316
Cat Servant
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In a word .... Don't.

Phase converters are outclassed by VFD's, or frequency drives. Single phase in, three phase out - and with added features like soft start and speed control.

Joined: Sep 2002
Posts: 910
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N
Member
Try going on the Arco Roto-Phase site. They are just one rotary converter manufacturer that came to mind.


http://www.arco-electric.com/SizingAssistance.cfm

Joined: Dec 2002
Posts: 318
S
Member
The Roto-Phase is a motor/generator which creates a 3rd phase through it's rotation. They work quite well for years without problems, but that being said Reno is right, the VFD is a much better product especially if you are on any sort of demand charge billing. The price of VFD's is good and they are readily available. I would install the VFD.

That being said, I have many 20 plus year old Roto-Phase sites that just keep plugging along and they will not be replaced until something dies.

I recommend TVSS protection on either installation.

Joined: Mar 2005
Posts: 1,803
Member
We had an extensive thread on this subject [Hill-billy saw miller [SP] /2003?] on various single to three phase options, including running big three-phase motors with a donkey motor etc, quite a few years back. If memory serves me right, aren't phase converters required to be rated at about double the expected demand?

Last edited by Alan Belson; 06/05/09 09:49 AM. Reason: spelling error

Wood work but can't!
Joined: Jun 2007
Posts: 301
J
Member
Originally Posted by renosteinke
In a word .... Don't.

Phase converters are outclassed by VFD's, or frequency drives. Single phase in, three phase out - and with added features like soft start and speed control.


Agree. Also, they are easy to size, by FLA, located on the nameplate. No moving parts and no maintenance other than a good vacuuming every so often. VFD's are much less money that a rotary converter, and easily installed and set up.

Try:
www.automationdirect.com
www.baldor.com
www.tecowestinghouse.com
www.wegelectric.com

Search the sites using keyword "AC Drives"

Joined: Jan 2004
Posts: 171
M
Merlin Offline OP
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I understand that VFD's are easier and less expensive but in this situation, there will be 5 new 3 phase loads added. So, wouldn't I need 5 VFD's or not?

Joined: Feb 2003
Posts: 939
F
Member
Originally Posted by Merlin
I understand that VFD's are easier and less expensive but in this situation, there will be 5 new 3 phase loads added. So, wouldn't I need 5 VFD's or not?


If they are all motour load and they are running the same time or not ? if not sometime it cheaper to get RPC instead of VSD's depending on motour size
But there is a major gothca almost all VSD are rated for one motour only so that something you have to think about it


Merci,Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Jan 2005
Posts: 5,316
Cat Servant
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5 VFD's or not? You ask as though that's a bad thing.

I bet you find that none of the three phase loads need to run at full speed - and that each has a different 'sweet spot.' In that instance, a drive for each unit is a real bonus. You also have enhanced reliability; one bad unit will not affect the other loads.

Joined: Feb 2003
Posts: 939
F
Member
That do make sense there.,

sometime it work the best like that way.

Merci,Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

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