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Author Topic: Wondering which gen to buy or use.  (Read 6817 times)

Dusty

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Wondering which gen to buy or use.
« on: June 15, 2008, 07:27:35 PM »
I've been reading and looking all over the internet and trying to make a decision on what generator to use for my 10/1.  I look on eBay and see the ST single phase and I also see the STC three phase.  I don't know enough about generators to decide on which one.  They can both make 120 or 240 volts.  Which one do most people buy?  I would say most of my needs would be 120, although I would like to run a air conditioner on 220.  I was reading that it might be best to run the generator on 120V then use a step up transformer to get 220V. 

Then of course I have my freebie Kurz and Root generator.  Its a 120/208 v unit.  The 208v has thrown me off as I see it might not be a good idea to run a 220 motor with 208.  I have a college student helping me figure out all this but he is just learning also, so I'm a bit lost on what to do. 

Also, what do the letters ST stand for.  I've looked all over and can't find the answer.  Nobody seems to know but everybody calls these generators the ST name.

Thanks, Mark

Stan

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Re: Wondering which gen to buy or use.
« Reply #1 on: June 16, 2008, 01:19:53 AM »
Oh boy, I can hardly wait for all the answers as to what ST stands for  ;D

As for 208 volts, simply google your air con manufacturer and or phone them and ask if 208 volts will harm it!
Stan

Doug

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Re: Wondering which gen to buy or use.
« Reply #2 on: June 16, 2008, 02:49:09 AM »
STandard
It's a Good Life, If You Don't Weaken

ronmar

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Re: Wondering which gen to buy or use.
« Reply #3 on: June 16, 2008, 02:58:54 AM »
You most likley want a single phase head.  The single phase head will give you one 220V circuit and/or two 120V circuits.  Think of it like a center tapped 220V transformer.  That is how most domestic services in most homes are powered.  The generator rateing, say 5KW can only be reached if the load is placed across the 240V circuit, or the two 120V circuits are equally loaded.  IE, a single 120V leg on a 5KW generator can only hold about 2.5KW of load.  Like a domestic power panel, the generator can provide 240 and 120 simultaneously, so you could run the AC on 240, wired hot1 to hot2, and provide for all the other 120V loads wired either H1 to neutral or H2 to neutral.  You of course want to keep those 120V loads balanced as best you can.  The neutral wire is the center tap of the generator windings, just as it is the center tap of the transformer out on the street feeding your home.  I have my ST wired right into my power panel at home with an interlocked circuit breaker(main must be locked off before gen breaker can be switched on).  I run 220V well pump, or stove burners, or even electric heaters if I want.  All the electrical outlets are hot and all the lights work as normal wether on generator or commercial power.  I do of course have to be carefull of what is allowed to run when on the generator.

A 3 phase generator has to follow the same rules as the 120V legs of the single phase generator.  Each leg can only support 1/3 of The total rated load of the generator, so a 10KW 3 phase can only handle 3.33KW per leg.

Ron    
PS 6/1 - ST-5.

Dusty

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Re: Wondering which gen to buy or use.
« Reply #4 on: June 16, 2008, 03:47:28 AM »
Now that I can understand, thanks for the explanation.  I just want to make sure I'm not making some costly mistake by jumping the gun and just ordering something without some kind of research.  Books can give great data but really don't offer much of an opinion, and that is what I need.

Thanks!

adhall

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Re: Wondering which gen to buy or use.
« Reply #5 on: June 16, 2008, 04:05:25 AM »
Dusty,

If you want to get 240 V from your 208 V generator, you could use a buck/boot transformer to raise the voltage. They are commonly used for just this purpose. You should be able to get one from any commercial electrical supplier.

Best regards,
Andy Hall
JKSon 6/1, 5 kW ST Head, 1992 Dodge RAM Cummins 5.9L Turbodiesel, 2001 VW TDI 1.9L Turbodiesel, 2006 Jeep CRD Turbodiesel, Yanmar FX22D Diesel Tractor

biobill

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Re: Wondering which gen to buy or use.
« Reply #6 on: June 16, 2008, 03:08:21 PM »
Quote from: dusty
Also, what do the letters ST stand for.
Thought it was Stamford Type,  after the origonal designer
       Bill
« Last Edit: June 16, 2008, 03:11:37 PM by biobill »
Off grid since 1990
6/1 Metro DI living in basement, cogen
6/1 Metro IDI running barn & biodiesel processer
VW 1.6 diesels all over the place
Isuzu Boxtruck, Ford Backhoe, all running on biodiesel
Needs diesel lawnmower & chainsaw

Petersbpus

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Re: Wondering which gen to buy or use.
« Reply #7 on: June 20, 2008, 09:26:29 AM »
This time arround ( for my Listeroid project)I bought  an ENW 6KW brushless with AVR (that was the smallest offered) from akatosborne on ebay, only planning to pull 3.5 off the 6\1 setup,, My previous project to run entire house 24\7  12KW ST head would only put out 104 volts under even a light load, so I ended up with the expense of a modern AVR to correct it. In my case they, them or some bad builder, must have left out some of the exciter windings, I'm sure many ST's out there put out properly but not mine, anything with a micro chip in it hated the low volt power, even the water heater which had the fancy selector control for vacation, energy saver ,away selector would not accept the low volts and had to have it's brain cut out to function after WILMA turned us off for 9 days.
I don't have any issues with the brushes ( except the crappy holders) and thier function, in fact if my brushless develops a problem I'm screwed, if I was dependent on it, but my 12kw 1115 Changfoid is the 24\7 unit for full grid failure, AND I wanted bearings prepacked with synthetic grease (very smooth ans spins nice by hand) and an AVR to satisfy those nasty little microchips with constant  voltage so they won't notice the HZ fluxuation so much, I'm hoping at least.
 Metro Listeroid is currrently down to bare block for sand removal and machine work improvement.

However I believe most A\C units will run on anything from 208 to 240, all my 5 ton portable units at work are marked exactly that, check your information plate. With an AVR you could bump the volts and split the difference, 218 to 220 would result in 130 to 135 on the 120 volt legs of your 208 unit, ( that ought to bring the SR members down on me!)
But the AVR also gets rid of the third world rectifyer.
You would need to do alot of balancing with the 3 phase head you have or waste effecency.
But if the 3.3 KW per leg isn't a problem for you I'd use it.

BTW I think ST stands for STupidly simple, Beware the screwed together Chinese rectifyer!!
Bob P
Listeroid 6/1 in progress
Alllis Chalmers 60KW 3 ph
Changfaoid 12KW w/  auto shutdowns, modern AVR and panel
2nd Changfaoid 12KW Marine conversion w/ full auto shutdown and remote panel
Changfaoid 7.7 hp driving 5kw alternater /inverter,
other diesel gensets bought fixed and sold

ronmar

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Re: Wondering which gen to buy or use.
« Reply #8 on: June 20, 2008, 06:13:59 PM »
but my 12kw 1115 Changfoid is the 24\7 unit for full grid failure, AND I wanted bearings prepacked with synthetic grease (very smooth ans spins nice by hand) and an AVR to satisfy those nasty little microchips with constant  voltage so they won't notice the HZ fluxuation so much, I'm hoping at least.

One thing I noted with the AVR experiments I have been conducting on my 6/1-ST5 is that the frequency excursions are larger with the AVR during load changes.  The flicker is greatly reduced, but load changes and an AVR feeding the field whatever it needs to maintain it's set output voltage make the mechanical load changes that are being applied to the engine much more severe.  This on a mechanical governed slow speed diesel makes for some larger frequency excursions.  With the normally harmonically excited head, a large load change is partially buffered by a voltage drop and the mechanical hit on the engine doesn't seem so severe.  The engine certainly seems to run more stable, and the engine dosn't puff as much black smoke after a large load change.  At least that is my impression.  Everything I try and run seems to be happy on the harmonically excited ST.  I coud see though if you were having a low voltage output from one how that could cause problems.
 
« Last Edit: June 20, 2008, 09:20:42 PM by ronmar »
PS 6/1 - ST-5.

Petersbpus

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Re: Wondering which gen to buy or use.
« Reply #9 on: June 20, 2008, 07:11:20 PM »
 good point, I have heard something like that before, there are alot of factors to consider, I'm going to put some of the shock start loads on my inverter and let that be the buffer, ( I'M putting a DC alternator on the Listeroid in addition to the AC head.) I hope the ramp(sensitivity) adjustment on the AVR could be set to compensate.
My big cooler refrigerator runs on 9 amps so the start is going to be quote high, that will be run off the battery bank and inverter, charged by the DC alternator.
We will see how it all pans out.
Bob P.
Dusty,,,
I have really no issues with my ST head, but if you have the time pull it apart and install grease fittings\change grease per utterpower CD it's a plus.
But lacking that, it's easy to monitor bearing temp with IR gun, to head off any problem.
one thing however with the 6kw head I  bought besides being prepacked with synthetic  grease and having a modern AVR, a substantial Dog house, it also had a higher insulation rating. I think those ratings are based upon temperatures that can be tolerated. I does have a welded base not a cast one which may be subjust to fatigue??
Listeroid 6/1 in progress
Alllis Chalmers 60KW 3 ph
Changfaoid 12KW w/  auto shutdowns, modern AVR and panel
2nd Changfaoid 12KW Marine conversion w/ full auto shutdown and remote panel
Changfaoid 7.7 hp driving 5kw alternater /inverter,
other diesel gensets bought fixed and sold

rcavictim

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Re: Wondering which gen to buy or use.
« Reply #10 on: June 21, 2008, 02:23:44 AM »
I think ST stands for Shorted Turns   :'(
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
-DIY JD175A, minimum fuel research genset.
-Changfa 1115
-6 HP Launtop air cooled diesel
-Want Lister 6/1
-Large DIY VAWT nearing completion