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Old 17-01-2015, 16:31   #1
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Autobalancing Transformer

we have a 9kw Beta generator which produces 240V / 60 hz (2x 120V legs ). We will have a single 240v breaker/ outlet near the gen for running a small welder occasionally. The main AC panel will be fed with 120v through a breaker style selector. So only 1 leg of the gen output, plus the neutral, will be used most of the running time.
My electrical consultant ( an AbYC master tech etc)mentioned that i may want to consider installing an autobalancing transformer to insure that i don't produce an unbalanced load on the gen windings. But, he also admitted this may be overkill for a <500 hr/ year gen installation.
Anyone with experience or direct knowledge of this have an opinion?
Thanks!


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Old 18-01-2015, 17:15   #2
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Re: autobalancing transformer

wow, i stumped the experts! i guess the silence is an answer in itself, meaning no one has ever heard of this. Autobalancing transformers are probably for high use generators. if i find out more I'll post the info.



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Old 18-01-2015, 17:33   #3
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Re: autobalancing transformer

Not sure what you are after...?? You are a Marine Service Provider with a ABYC master tech consulting with you on electrical usage of your generator and you come to an Internet forum for advice????

It's your generator. If you want to utilize only half of it and be limited to 4.5kva for your house loads that's your choice.
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Old 18-01-2015, 17:38   #4
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Re: autobalancing transformer

What is the load capacity of the 120 volt panel? If it is small compared to the 9KW capacity of your generator the imbalance may not be as big a problem as running the genset with too light a load. For example, if it is 4.5 KW that leg will be maxed out and the imbalance would cause wear on the bearings in the motor. If it is 1 KW the load would be too light for efficient operation of the motor.

I would at least look into the cost of a 240v-120v transformer sized to your panel load.
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Old 18-01-2015, 17:53   #5
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Re: autobalancing transformer

Auto balancing g transformer. ??? It's just a 240 -110v step down

Dave


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Old 18-01-2015, 18:09   #6
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Re: Autobalancing Transformer

It is likely you can reconnect your generator and your welding machine for 120 volts.
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Old 18-01-2015, 19:58   #7
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Re: Autobalancing Transformer

Firstly, I don't know why Cruisers Forum deemed it appropriate to tag me a Marine Service Provider. I'm a bloke building a boat. I have a website. Guess that makes me an expert.
The AC load will be 30-40A (shorepower=30A, Genset =40A)at 120V (36-48KVa). I understand the need to load the engine a bit, so when running the genset we'll be heating water and/or running the HVAC and/or charging the batteries and/or running the water maker and/or washing clothes, etc.
Victron makes a 32A and a 100A unit, primarily designed, it appears, for when there is both a 240V and a 120V load. My main AC panel is all 120v. The 240V will be a small auxiliary nearby the geneses with an outlet for the welder.
I'm going to talk to Victron and to Stanley at Beta. But St. Elsewhere intimates he thinks it might cause a bearing wear issue…which is what I'm concerned about.
Thinking of the issue in terms of a step-down transform is helpful, thanks.

I'm using this forum to access other folks experiences. Occasionally I may be able to offer my experiences that will help someone else to make their decisions. I'm not looking for an" answer" to a question. The whole boatbuilding process has been a giant, fascinating search for knowledge. After 10,000 hours/6 years of building, I'm pretty sure I've got one or two bits of knowledge tucked away somewhere. I try to do things the best way I can figure out, by doing research, experimenting and , uh, asking lots of dumb questions. Thanks.
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Old 18-01-2015, 20:12   #8
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Re: Autobalancing Transformer

Another thing to consider in running an out of balance load, is the neutral will carry much higher amps, and thereore you need to make sure the cable to the panel and the neutral breaker can handle the out of balance load.

Lloyd

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Originally Posted by Brian Russell View Post
Firstly, I don't know why Cruisers Forum deemed it appropriate to tag me a Marine Service Provider. I'm a bloke building a boat. I have a website. Guess that makes me an expert.
The AC load will be 30-40A (shorepower=30A, Genset =40A)at 120V (36-48KVa). I understand the need to load the engine a bit, so when running the genset we'll be heating water and/or running the HVAC and/or charging the batteries and/or running the water maker and/or washing clothes, etc.
Victron makes a 32A and a 100A unit, primarily designed, it appears, for when there is both a 240V and a 120V load. My main AC panel is all 120v. The 240V will be a small auxiliary nearby the geneses with an outlet for the welder.
I'm going to talk to Victron and to Stanley at Beta. But St. Elsewhere intimates he thinks it might cause a bearing wear issue…which is what I'm concerned about.
Thinking of the issue in terms of a step-down transform is helpful, thanks.

I'm using this forum to access other folks experiences. Occasionally I may be able to offer my experiences that will help someone else to make their decisions. I'm not looking for an" answer" to a question. The whole boatbuilding process has been a giant, fascinating search for knowledge. After 10,000 hours/6 years of building, I'm pretty sure I've got one or two bits of knowledge tucked away somewhere. I try to do things the best way I can figure out, by doing research, experimenting and , uh, asking lots of dumb questions. Thanks.
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Old 18-01-2015, 20:46   #9
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Re: Autobalancing Transformer

Your generator is a 1800rpm 4-pole alternator. Producing 240v, the 2 windings are strapped in series and the 120v neutral tap is connected in the middle of the 2 windings. By putting all the load on 1 of the 2 windings that winding is producing all the heat. It would be much better to share the load across both windings keeping the heat produced to a minimum.
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Old 18-01-2015, 21:18   #10
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Re: Autobalancing Transformer

Cap EricT you may have the best solution! there is a diagram in the Marathon generator portion of the owners manual showing how to connect T1, T2, T3 and T4 to produce 120v, which, i presume , would be balanced. The small welders like the Dynasty 200 don't get de-rated too bad when run on 120v .


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Old 18-01-2015, 22:22   #11
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Re: Autobalancing Transformer

Just a thought, but could set up your boat’s AC panel like a residential panel using both 120 legs this would more evenly load the generator. But then again it may be easier to reconfigure the generator output.
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Old 18-01-2015, 22:39   #12
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Re: Autobalancing Transformer

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Cap EricT you may have the best solution! there is a diagram in the Marathon generator portion of the owners manual showing how to connect T1, T2, T3 and T4 to produce 120v, which, i presume , would be balanced. The small welders like the Dynasty 200 don't get de-rated too bad when run on 120v .
Brian,

This may be a good option. It also means that 9 KW @ 120 volts requires that wiring carrying the full load needs to be based on 75 amps for both voltage drop and load capacity computations.
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