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Tool Talk Discussion Forum

Delta vs. Wye alternator circuits

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Darren in TN

03-29-2004 21:03:31




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Hey, folks.
I've got an old alternator I've been playing with here in the shop and it has me a bit confused. Being from a small truck (it's the 60 amp alternator from an older Toyota 4x4) I assumed it would be wiried up with the three coils in a Wye (star) configuration. However, it has four posts on the rectifier-- one lead from each coil and a common ground for all three. That makes it a Wye with a central ground. When I diagrammed that, it looked to me like it would be the same as a delta wired alternator. I've gotta be missing something though. Can you three-phase guys correct me on this? The reason I ask is I'd like to convert it to a delta config to multiply current by 1.73 so that I can run it unregulated as a welder. If it's already functioning like a delta wired alternator there'd be no point in the excercise.

Thanks folks,
Darren

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buickanddeere

03-30-2004 07:59:44




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 Re: Delta vs. Wye alternator circuits in reply to Darren in TN, 03-29-2004 21:03:31  
Sory but it's not a very practical exercise as 60Amp for welding is pretty light and when the rod sticks the alternator is really going to hurt. For the same line current a Y machine has more phase current than a delta machine. As for rectification it will use four posts/three diodes being Y. A delta needs 6 diodes or three bridge recitifiers to get DC. A Delta machine for the same amount of power has higher voltage and less current on each internal winding. Smaller lighter machine.

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Darren in TN

03-30-2004 10:51:05




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 Re: Re: Delta vs. Wye alternator circuits in reply to buickanddeere , 03-30-2004 07:59:44  

BuickandDeere,
Thanks for the info. The rectifier is a bit different than you suggested-- stock, it uses four posts and eight diodes. I don't expect it to weld 1" steel, but it ought to at least be an interesting project. The real question I'll have to answer experimentally is whether the stock diodes can handle the voltage... When I disconnect the voltage regulator in order to weld, the open circuit voltage will probably be in the 100 to 150V range. I believe most american-made alternators burn their diodes around 30V (so I'm told), but nobody has been able to tell me yet whether Toyota put in stouter diodes. I do know that some diodes in big diesel applications can handle up to 200-300V. I'll have my hand on the kill-switch, lol.

Thanks,
Darren

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Mark

03-30-2004 09:19:34




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 Re: Re: Delta vs. Wye alternator circuits in reply to buickanddeere , 03-30-2004 07:59:44  
Well spoken buckanddeere. I just checked your answer in my Flanagan "Handbook of Transformer Applications" just for grins as I am having lunch and surfing the site while doing so. I'm impressed that you know that. Course, I have no idea as to your background and on this sight they ARE extremely varied.

Mark



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buickanddeere

03-30-2004 11:52:35




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 Re: Re: Re: Delta vs. Wye alternator circuits in reply to Mark, 03-30-2004 09:19:34  
Mark thanks. Usually someone gets upset when I tell them a cheap and quick short cut won't work and is dangerous. Not to say I don�t make a few typos, grammar and spelling mistakes along the way. I'm just a licensed industrial electrician, college grad in the electrical field, have a CFAA Fire Alarm ticket and work on nuclear reactor control and power systems. And I still can't people to believe that the ground and neutral wires are two different lines with two different functions. And trying to explain a 12/24V. Deere electrical systems���.. The delta can be rectified using two diodes back to back per terminal for a total of six. Two more back at the common point can't hurt if one of the individual phase diode pairs short out. Running the alternator past rated voltage will smoke the field/brushes,slip rings due to high current. The max they should see is 14.4V. Pushing diodes past their break-down voltage just wounds them and will sooner or later bring on a shorted diode. They are power diodes, not zenors which are built for that abuse. Alternators rated for e.g. 120 amps is very optimistic. For 5 minutes yes, then current should have dropped back as the battery starts taking a charge. I wouldn't try to take 1/2 of an alternators rated power on continuous duty . Less if under a hot engine hood.

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Mark

03-30-2004 12:16:54




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 Re: Re: Re: Re: Delta vs. Wye alternator circuits in reply to buickanddeere , 03-30-2004 11:52:35  
I was off surfing other e sites while thinking about what you said concerning not knowing the difference between white and black. Have to share this with you.

I was pres of the local water supply corp (community service) and had a new member trying to hook up his water pump. Called and said that everytime he reset the breaker and attempted to turn it on, the breaker popped.

Went to his house and checked out his system. Everything seemed pretty straight forward except where he wired in his pump. The white, black, and bare were all twisted together and that wad was taped over. LOL.

Mark

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Mark

03-30-2004 12:08:29




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 Re: Re: Re: Re: Delta vs. Wye alternator circuits in reply to buickanddeere , 03-30-2004 11:52:35  
I did too (spelling error in previous reply) just now on the word sight; should have been site where I referred to people you meet on this site.

On credentials, again I'll say never know to whom you are speaking; pays to be a bit humble; I try to be but at 62 it's tough (think you know it all).

I build (built) things running off 3 phase 400Hz that have (had) lots of magnetics, energy storage devices, high voltage and all. Really liked to move energy around and then bingo; consume it.

Enjoyed the short chat.

Mark

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