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7 comments
Member

Join Date: May 2008
Posts: 6
Good Answers: 1

Three-Phase to Single-Phase Conversion

02/05/2010 8:15 AM

Hello All. I want to convert the output of my 3P generator to 1P. Since it cannot be re-wound, is there a way to do the conversion either by Inverter technology, or via some sort of transformer? It is 220V, delta wound, 15kva. I have wired it to feed 3 separate panels, using UV, VW, and WU, but it is extremely hard to balance the phases.

I only have 3 needs for 3P, namely the windlass, capstan, and dive compressor. All of the other demands are 1P throughout the vessel. I am going to assume that an inverter type unit will be the best light-weight solution, but all of my searches have turned up with zero information. Search engines tend to "invert" the search to convert 1P to 3P!

When tied up to the pier, all of the sources are 1P. With 1P Shore power, only one switch is needed if the genset is also providing 1P. However, when using my present system of pulling 220V 1P from each winding, it becomes an electrician's nightmare.

Thank you in advance for any suggestions and solutions you can offer.

BobF

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#1

Re: 3 Phase to Single Phase Conversion

02/05/2010 9:14 AM

Is there a neutral conductor connection on the generator output terminals?

  • If there is, then phase-and-neutral can be used without modification if the voltage is correct.
  • If not, then a transformer wired across 2 of the phases converting that particular voltage to whatever single-phase voltage is required, with the adequate protective devices in-circuit of course, is all that is needed. With a greater load on the above two phases, though, expect the voltage on them to be a bit lower than that on the other phase conductor while the single-phase transformer is loaded.

"If in doubt, consult a qualified electrician."

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Join Date: Jun 2007
Location: New England
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#2

Re: 3 Phase to Single Phase Conversion

02/05/2010 9:24 AM

The single phase loads are derived from pairs of legs and the load is balanced out by the distribution. I can see that your problem is a low and fluctuating single phase load(s). Rather than getting something that would be quite expensive and cumbersome, I would suggest setting up a motor-generator set (rotary converter), i.e., an appropriately sized three phase motor driving a small single phase generator that will handle all single phase load. It's not the most efficient way of doing it but it will probably be the most cost effective.

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Member

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Posts: 6
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#5
In reply to #2

Re: 3 Phase to Single Phase Conversion

02/06/2010 6:03 AM

Thank you for that idea. I would like to solve this problem with as little weight addition as possible. That is why I thought there might be an electronic solution in the way of Inverter Technology. I have on board 2 VFD's that do yeoman's duty for the windlass and capstan when 3P is not available directly. By that, I mean, if the main 3P genset were to quit, I could power the 3p windlass/capstan via a 1P to 3P VFD, using either the cruise generator (1P) or the 24V DC Inverter (1P). The VFD's are 3hp rated, and allow either 1P or 3P input. I need this type of redundancy. Therefore, I thought, if one can go from 1P to 3P with that technology, why can't I go from 3P to 1P the same way? For example, I know there are units that use an alternator belted off the main engine that convert the pulsating AC from the alternator to a sine wave 220V output for the house supply. They come in various outputs up to about 12KW. These work over the entire RPM range of the engine, and only the Output KW rating varies. It appears to me it is a simple jump from that technology to what I need. After all, my 13KVA is probably the equivalent of about 10KW, which is within the range of the above-mentioned alternator supplied power. Is there anyone on this forum up to date on this idea of conversion from 3p to 1p? I thank all who are taking an interest in this...a marketing idea in the making? BobF

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Guru
Canada - Member - Specialized in power electronics

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#6
In reply to #5

Re: 3 Phase to Single Phase Conversion

02/06/2010 10:21 AM

Yes, there are electronics converters. I have a few in the shop. The problem is that they are very expensive. The technology is similar to VFDs but is produces in small quantity so the price is higher. There are other suggestions posted here that are much more cost effective. If they don't apply, click on my name and drop me a line. We do this from 50A to 2000A. 240V to 4160V. 1ph to n ph.

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Guru
Canada - Member - New Member Hobbies - Musician - New Member

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#7
In reply to #5

Re: 3 Phase to Single Phase Conversion

02/06/2010 3:03 PM

Suggest you contact Asea Power in huntington CA. they make products specifically for what you need and their main market is big boats. They use double conversion electronic inverters for light weight.

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#3

Re: 3 Phase to Single Phase Conversion

02/05/2010 11:02 AM

Use a set of single phase transformers to give you a 1:1 isolation and then you can set their outputs up in a 'Z' configuration to get the full single phase power equivalent out of it.

I have an old military gen-set that can have it windings connected that way for full single phase output power. Its a fairly common phase balancing technique on most multi tap or multi configuration generators.

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Join Date: Feb 2010
Posts: 1
#4

Re: Three-Phase to Single-Phase Conversion

02/06/2010 5:48 AM

Dear sirs,

I think the best idea using load bank to get good load balance of power generator.

thanks

fakhri

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