Lister Engine Forum
Welcome, Guest. Please login or register.
December 17, 2014, 11:01:43 pm

Login with username, password and session length
Search:     Advanced search
Welcome to the ALL NEW Lister Engine Forum - just like the old one, only somewhere else...

Photo gallery - www.listerenginegallery.com
72369 Posts in 5844 Topics by 3500 Members
Latest Member: londonron
* Home Help Search Login Register
+  Lister Engine Forum
|-+  How to / DIY
| |-+  Generators
| | |-+  3 phase generator to single phase conversion?
« previous next »
Pages: [1] Print
Author Topic: 3 phase generator to single phase conversion?  (Read 7519 times)
twombo
Jr. Member
**
Posts: 82


View Profile
« on: October 04, 2007, 10:43:24 pm »

Got a really good deal on an ONAN genset, a 7.5 kw  model DKD.  It's three phase though, instead of single phase.  I'm awaiting service and maintenance manuals.

My main question is, is it possible to reconnect the three phase alternator to put out straight single phase power?

I have wired it in to three separate load centers, all sharing a common neutral, but the loads (my small woodshop)  are intermittent (although fairly well balanced when all are running).

Problem is, the loads are very intermittent and the operator manual for the gen set specifies a balanced load (phase to phase) within 10 %.  Obviously if I have 15 amps on a phase and on B and C,  it ain't balanced.

The genny is placarded  at 23 amps for a single phase or a maximum of 26 amps/phase in 3 phase operation.  ( I will double check the numbers).

Thoughts?  The three phase just happened and it would be hard to turn down free genset.  Single phase would be be more flexible for me. I also don't want to break the genny by running it in a completely unsuitable manner! No sense being stupid in the face of good fortune!

Thanks

Mike
Logged
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #1 on: October 05, 2007, 12:23:58 am »

Wait for the manual....

in the mean time how many leads does it have? ( just 4, 3 phases and a neutral and you commited to 3 phase ).

Doug
Logged

It's a Good Life, If You Don't Weaken
twombo
Jr. Member
**
Posts: 82


View Profile
« Reply #2 on: October 05, 2007, 01:52:19 am »

Good sign, Doug,  It has 12 wires (T1 thru T12) coming out of the head!! It must be what Onan/Cummins calls a "broad range".

I'm waiting (sorta) patiently.

I got the wiring diagram numbers off the control box so I will press ahead with getting copies of those and... waiting! There is a reconnection diagram inside the control box lid.

I'm not doing anything till the manuals arrive but a couple quick questions:

1. On a standard reconnection diagram, the electronic symbols depicted as coils are the alternator windings themselves.

2. Wired as a 2 wire output, (L1 and L2), the the output would be 120 only  or if wired as a 3 wire output (L0, L2, and L2) there would be a 120/240 capability.

I did another search in the archives and found another discussion on three phase. I feel like a real dink not researching better. DUHH!

How is the little QA dude?

Mike
Logged
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #3 on: October 05, 2007, 02:30:21 am »

Sounds like a good deal.

3 phase is much handier than most people think. Its easier to find motors and just requires a little planning for other loads.

Wish I had 3 phase in my home......
Logged

It's a Good Life, If You Don't Weaken
twombo
Jr. Member
**
Posts: 82


View Profile
« Reply #4 on: October 05, 2007, 02:54:09 am »

Doug

That's how I have wired it in so far (utilizing the three phases to a distributed set of loads in the power room and the shop), but what about unbalanced loads? The  Operators manual specifies balanced loads within 10 percent.

In my case,70% of the time it has 20 amps or less on A phase, (decreasing as  the inverter charger tops off the batteries) and 0 amps on B and C. Periodically I'll have 10 or 15 on B and C and a light load on A.

I've laid things out so that I don't exceed the max on any phase or the total placarded rating under any circumstance. Full load on all legs run should be in the mid 80% range. The load usage is pretty solidly in the "Standby" category rather than a Prime type load.

At some point, I may get a 3 phase VFD spindle for the CNC and then I am golden withe little Onan genny. I agree, It can be very handy!

I might just be being too conservative.

I really appreciate you sharing your knowledge!

Cheers

Mike
Logged
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #5 on: October 05, 2007, 03:22:34 am »

Ballance is a bit of an issue, you can hear it in the machine when running if you have two phases or one pphase more heavily loaded than the others. This makes voltage regulation a bit of a problem since you can't crank upi the voltage on the loaded phase to compensate without and over volt on the the lightest.

Same trouble with the Eddison 3 wire system ( common 120/240 volt ) if you load on half more than the other....

I blame Eddison for everything....

You don't gain anything like the extra cooling jens.
The killer of all electrical equipment is the hot spot temperature of that one area that runs the hottest and cools the least well in a winding. They just can't shed heat from where ever that spot may be effectively. The only way you can increase the power rating would be to cool more ( with much cooler air or a lot more air flow )
Logged

It's a Good Life, If You Don't Weaken
twombo
Jr. Member
**
Posts: 82


View Profile
« Reply #6 on: October 05, 2007, 03:43:13 am »

Thanks Doug

That pretty much clinches it for me then.  When I get manuals in hand, I'll reconnect it for 120 volt, 2 wire, since I have no Eddison requirements. That way each winding gets equal treatment.

Like I said, just because I got a great deal, I don't have to abuse it. It has electronic regulation, so no sense killing a pricy regulator  board.

There is another unit like this up the hill in a lighting  cart one I can get for a song and it is 120/240 (Eddison?).  I can always take this one back to three phase if I get a high frequency spindle.


Mike

Logged
listerdiesel
Guest
« Reply #7 on: October 05, 2007, 05:18:47 pm »

12-wire reconnectable is pretty much industry standard for machines that have the facility to run at single or three-phase, but you will not be able to pull full power at single-phase connection, this is due to the out of phase element of the windings in series.

I think you get about 60-70% of the three-phase power.

Peter


Logged
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #8 on: October 05, 2007, 08:53:03 pm »

You have that in tha UK as well Peter?

I'me trying to come up with a combination in my head that will give you 380....

Seems to me if you reduce the speed and excitation a little this same set would probably also generate 380 5o hz. Do they do that in Eroupe?
Logged

It's a Good Life, If You Don't Weaken
listerdiesel
Guest
« Reply #9 on: October 07, 2007, 11:04:27 am »

You have that in the UK as well Peter?

Yes, as I said it is pretty much a standard build for a lot of machine makers.

I'me trying to come up with a combination in my head that will give you 380....

You can play with the figures, but the easiest seems to be a convertible 120/208 or 220/380, and you'd probably need to speed up from 50hz to 60hz in there somewhere to get the AVR to cope (and back again)

Seems to me if you reduce the speed and excitation a little this same set would probably also generate 380 5o hz. Do they do that in Eroupe?

The basic winding sets are pretty adaptable, but AVR drive is crucial if you're going to run at lower rpm/hz so you need to make sure that your field windings and AVR can cope at the lower speed, and have the cooling as well.

KATO machines were nearly always specced as 12-wire, and Onan also did them on the larger alternators.

The machine you have in your hand ALWAYS just doesn't 'quite' do what you want......

Peter
Logged
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #10 on: October 07, 2007, 04:50:12 pm »

That is the beuty of the rewind shop.

If it wasn;t exactly what you wanted, it can be for price Roll Eyes
Logged

It's a Good Life, If You Don't Weaken
listerdiesel
Guest
« Reply #11 on: October 08, 2007, 01:04:10 pm »

That is the beauty of the rewind shop.

If it wasn't exactly what you wanted, it can be for price Roll Eyes

You can't always rewind a three-phase stator to single-phase, or a 3-phase rotor to single-phase, just as single-phase transformers and 3-phase transformers are mechanically different, there are different winding slot arrangements on generator rotors and stators.

I have seen it done, but it was not an easy job on this particular unit (Markon)

Peter
Logged
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #12 on: October 09, 2007, 12:43:31 am »

I can't say I recall any specific machine I couldn't rewind for a voltage change . Pole changes can be trickier(  I was forced to do some odd grouping from time to time and not many people will go to the trouble to calculate an odd grouping although there are probably spread sheets and programs now for this )

The real killer is the slot pole numbers.
Some work fine, some cause a Cusp ( hard to get the motor up to speed )
Some cause cogging.
Some are just plain noisy.

Single to three phase is easy.
Three phase to single is sometimes complicated in motors when you have to cook up an AUX winding. I never had set of tables for this so I guessed based on winding data from simmilar motors.

I don't believe I ever did any single to poly phase conversion of generators.
Generaly there are tables that will tell you what you can and can't do. Then you plug the numbers into a master formual and start grinding numbers ( had TRS 80 my old boss wrote a lot of programs for to do this )
Doug
Logged

It's a Good Life, If You Don't Weaken
Doug
Hero Member
*****
Posts: 3386


Why don't pictures ever work for me?


View Profile WWW
« Reply #13 on: October 10, 2007, 07:11:20 pm »

Yes, see also
http://www.anoldman.com/modules.php?name=Articles&page=generator.html
and follow the derating
Logged

It's a Good Life, If You Don't Weaken
Jim Mc
Sr. Member
****
Posts: 330



View Profile
« Reply #14 on: October 11, 2007, 01:19:28 am »

yep.  zigzag works fine.  Just don't exceed the winding's rated current.  Generally, the kVA available will be less than the 3-phase spec. YMMV, especially with some of the military sets, as they carried their full ratings in single phase. 
Logged
Pages: [1] Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.12 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!