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Author Topic: Gen Head Sourcing  (Read 10148 times)

mcreeferson

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Gen Head Sourcing
« on: February 06, 2016, 01:49:02 AM »
I am looking at picking up a head, and think I will be going brushless. It seems that Central Georgia Generator is fairly popular here, any other recommendations? Powerhouse Diesel Generators? Are they just the same units in different paint? Marathon heads seem to have a good rep, but they are more than double the cost from what I have been able to find for published pricing. Is there a middle ground out there?

To open another whole can of worms for discussion, I have actually been toying with the idea of getting myself two heads, a single, and a 3-phase. My thought was I could power some 3-phase gear I have currently have running in the shop on a phase converter with that head, and just leave the single phase unit spinning free. As long as I'm not drawing power, it is just more flywheel weight right? When I need backup power, all I need to do is plug it in. I know I can power some single phase gear with a 3-phase head, but from what I have researched so far, that is less than ideal due to imbalance issues. I also don't want to be out rewiring the thing every time I want to make the switch between modes of operation (shop or backup). I probably won't come anywhere near taxing the unit with my 3-phase requirements, not much to run there, but I want to be able to pull every kW this rig will give me when it comes time to run as a backup.

I know there are a lot of variables here, but I'd be interested in hearing what the crew has to say on this stuff if you don't mind chiming in.

Thanks boys.

dieselgman

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Re: Gen Head Sourcing
« Reply #1 on: February 06, 2016, 05:20:01 AM »
An imbalance in loading is always preferable to be avoided, but if you simply oversize your 3-phase head then you will have maximum flexibility with a safety margin for any load imbalance that might occur. It is fairly common for a simple rotary switch to be wired for changing the thing from 3-phase to single-phase connections. Most of the Marathon heads whether rated single or 3-phase are using the same internal windings (rated according to size and capacity) - are all basically 3-phase internally anyway. The differences are in rating and external connections only. Other manufacturers have tended toward dedicated internal wiring for either single or 3-phase without providing for as much field modification of the windings and wiring schemes.

Most, if not all,  of the major manufacturers have also gone to Chinese production... this includes Marathon and Stamford and the major name-brand equipment that Lister/Petter has been packaging for quite some time now. It is a global market place, and while there are possible pitfalls to overcome with some of the lower-end Chinese stuff, it is predominantly of good quality when talking about any of the name brands. This tends to be a true case of "getting what you pay for" as long as you source from reputable people and also do your homework.

At Diesel Electric we specialize in small-scale power generation. Apart from massive Lister/Petter stocks, we also keep many hundreds of generator heads of all flavors in stock between our Kansas and Alaska warehouses. We provide first-rate customer service and support for all our products and have long experience making this stuff work in all environments.

dieselgman
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mcreeferson

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Re: Gen Head Sourcing
« Reply #2 on: February 06, 2016, 04:11:49 PM »
Gman,

I was halfway thinking about going with an oversize 3-phase unit, but wasn't sure if it would be an ideal solution, maybe I need to do some more reading.

Glort,

I have a converter running the saw now, and it does the job, but, when I plug it into true 3-phase, the power difference is clear. From my previous reading, I got the impression that while running 3-phase gear of single phase power is doable, it always results in somewhat lower power yield. I want that power at home.

mcreeferson

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Re: Gen Head Sourcing
« Reply #3 on: February 06, 2016, 04:41:08 PM »
Maybe a single oversize 3-phase marathon head is what I will go after. I understand that just about everything is made in China these days (like it or not), but I just want to try and get something that, regardless of where it is made, is held to some sort of decent qc standard. I don't mind swapping out bearings and the like at the outset, so long as I can count on trouble free operation after my initial investment of due diligence. Doing all that, only to have it fail in operation during an outage in a crazy winter storm, after only a short amount of time due to overall sub-par components and workmanship is what I want to avoid.

dieselgman

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Re: Gen Head Sourcing
« Reply #4 on: February 06, 2016, 08:20:57 PM »
Your power yield should be determined by the horsepower of your prime mover (regardless of load balancing and 3-phase vs single-phase power)... NOT the limitations of the generator head. Go with an oversized 3-phase and you can do whatever you want with it including pulling both 3-phase and single-phase loads at the same time. Switching for proper selection of high-voltage may be required though...

dieselgman
« Last Edit: February 07, 2016, 02:19:33 PM by dieselgman »
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mcreeferson

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Re: Gen Head Sourcing
« Reply #5 on: February 07, 2016, 03:41:29 AM »
In my application, my 3-phase gear runs at 240, and my backup power would of course be 110/220. To pull both 3-phase and single phase simultaneously, or either/or without wiring changes, it seems that a low voltage wye configuration on a 12 wire head would come closest to nominal. Are the numbers produced there close enough to nominal to work? Can I run my home using two legs and neutral (120/208) safely? Is it ok to run the 240 stuff in the shop (motor loads) at 208, or do I risk shortened life or sacrifice power with this arrangement?

It seems like a voltage changeover switch might be a better choice in my case? Switching between high series delta, and a zig zag arrangement seems like the ideal solution for my needs. In the event that I am using my rig for backup generation, losing 3-phase capability is not an issue to me. So toggling between, but not having both simultaneously, is not really a drawback. What is more important to me, is having a fully operational homestead in an outage, so 120/240 capability is key.

So the million dollar question is, assuming a reasonably balanced panel in the house, how much headroom should I allow myself to avoid potential problems with overheating in a zig-zag configuration? It's no longer just a simple 1/3 derating when you throw some potential imbalances my breaker panel into the mix correct?

dieselgman

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Re: Gen Head Sourcing
« Reply #6 on: February 07, 2016, 02:18:01 PM »
A selector switch would be the best arrangement. Also, compatibility of 208vac would depend on those specific load devices. Some will be found compatible and others not so. I believe that most older style induction motors will heat up unacceptably at lower than rated voltage. Pure resistance loads like hot water heaters and such will simply produce a bit less Wattage and heat more slowly.

For rating purposes, a balanced load is assumed. However, if you are looking at the 3-phase rating and it is accurate for the head, then a 25% to 50% oversize would take care of most moderate imbalance issues. I am not sure exactly what the engineering rule of thumb in general practice is, but it will be based on the designed insulation temp rise in the head (insulation class). From experience in our school installations, the engineers go for the 50% figure in general so that even fairly large imbalances will not be possible to damage the equipment.

dieselgman
« Last Edit: February 07, 2016, 02:20:59 PM by dieselgman »
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mcreeferson

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Re: Gen Head Sourcing
« Reply #7 on: February 08, 2016, 12:47:56 AM »
Thank you for the help. Having people to bounce this stuff off of is great.

Regarding a switched voltage arrangement, where are these normally sourced? This is obviously a bit of a specialty item, and precious little comes up in web searches, precious little of any use anyway...

dieselgman

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Re: Gen Head Sourcing
« Reply #8 on: February 08, 2016, 03:15:55 AM »
That rotary switching is common in older portable and rental equipment... best place to find affordable will be on used generator trailers - auctions and such, used equipment dealers, not too much held any longer in scrap yards that I have been able to find. I believe we have a few examples around but that is not in our regular electrical stocks as we are not often asked to accommodate your specific design... I am sure that can be reliably sourced and replaced new though. Defining the exact particulars for a 12-lead and the swap from Delta to Zig-Zag will take a little figuring and also must have adequate contacts for the size (current rating) head you will be switching. The smarter ones I've seen actually include a lockout to prevent switching during set operation, and I have also seen some with a "plug" design that seems pretty fool-proof and simple.

I am in Kansas for the winter and all of our trailer mounted rental equipment is in Alaska so I cannot easily just go and look up a part reference for you... but I will see what I can do regarding the parts books.

dieselgman
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38ac

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Re: Gen Head Sourcing
« Reply #9 on: February 08, 2016, 12:42:41 PM »
Hi,
I am doing exactly what you first proposed, or more exactly getting ready to as we are construction in progress.  My prime mover is going to be a 31HP Blackstone MP at around 700 RPM. I purchased a brand new 40KW 3 phase head at auction for cheap which will run the machine tools in the shop. Also have a 15KW single phase head on the way from Gary that will provide both stand by power for the house and single phase needs for the shop. In addition  so we dont have to run the big engine just to run the house the single phase head will be located between the Blackstone and another smaller HP diesel engine. We have several types of slow speed to choose from for that and have yet to make that decision.  By moving the belts we will be able to supply single phase needs by either either engine depending onwhat else is going on that day.  Certainly not the most cost efficient way to do things if all the parts and pieces had to be purchased at retail but I already own the engines and want to put them to use.  Once construction commences I plan to start a thread and have some pictures.  :)
Collector and horder of about anything diesel

mcreeferson

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Re: Gen Head Sourcing
« Reply #10 on: February 18, 2016, 09:57:17 AM »
I am looking at switches and wiring options now, and am a bit confused. Over in this thread http://listerengine.com/smf/index.php?topic=6219.0, it sounds like DD (double delta) will only provide 120v, with no 240 capability. However, some of the documentation I am looking at seems to indicate otherwise. I am wondering if I am reading the documentation wrong, or misunderstanding the posts in that thread? From the documentation I will post below, it seems that DD provides both 120 and 240, it is a separate configuration altogether "Low" or "Parallel" Delta that would provide 120 only (3-Phase).

Set me straight please...



dieselgman

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Re: Gen Head Sourcing
« Reply #11 on: February 18, 2016, 01:09:20 PM »
Correct... at 60Hz Parallel low Delta will be 120vac only... Double Delta will provide 120/240.

dieselgman
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buickanddeere

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Re: Gen Head Sourcing
« Reply #12 on: February 18, 2016, 07:52:32 PM »
Forget about the Delta . The 12 wire Y  configuration  is the only practical connection. A funky selector switch selection allows the three phase generator to output true single phase 120/240 power instead of 120/208.
   

mcreeferson

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Re: Gen Head Sourcing
« Reply #13 on: February 26, 2016, 05:38:57 PM »
For future reference, I have been in contact with www.controlswitches.com and was quoted just under 300 bucks for a custom built, padlockable, 100amp per phase (@ 240) rated 2 position voltage switch, with 2 outputs, and 3 auxiliary contacts per position for voltage sensing connections.

mcreeferson

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Re: Gen Head Sourcing
« Reply #14 on: May 06, 2016, 11:35:28 AM »
Still working out the AVR connections, and I wont truly know until I have her running under load, but so far I am happy I ordered that switch, nice and clean solution...