- Thread starter IaLeo
- Start date
Sorry Leo, this is beyond my pay scale and expertise. I will defer to other more current and more "electronic" minded gents such as JD and Bob and Bob M and janicholson and JMOR and Soundguy and drsporster and Dusty etc etc etc etc and several others.
THAT BEING SAID AND FWIW (Nothing) I will say:
You mentioned "RECTIFIED" well if an AC source is indeed rectified to pure good quality DC then, of course, it can be connected in series and/or parallel to increase voltage or power etc etc.
HOWEVER if its still AC, YOU CAN NOTTTTTTTTT start connecting sources together until the frequencies are synchronized or else indeed as you asked IT AINT GONNA WORK.
That's all I have to say about that (see the movie Forrest Gump) and hopefully the fine sparky gents who know more about those generators or research and google it and educate themselves can better answer your question, Im NOT your man, but hey I try anytime I can lol
John T Too old n too long retired EE
THAT BEING SAID AND FWIW (Nothing) I will say:
You mentioned "RECTIFIED" well if an AC source is indeed rectified to pure good quality DC then, of course, it can be connected in series and/or parallel to increase voltage or power etc etc.
HOWEVER if its still AC, YOU CAN NOTTTTTTTTT start connecting sources together until the frequencies are synchronized or else indeed as you asked IT AINT GONNA WORK.
That's all I have to say about that (see the movie Forrest Gump) and hopefully the fine sparky gents who know more about those generators or research and google it and educate themselves can better answer your question, Im NOT your man, but hey I try anytime I can lol
John T Too old n too long retired EE
dr sportster
Well-known Member
Bob M
Well-known Member
A nephew who works on turbines for GE gave me tour of an 18 x 1.5 MW turbine farm a couple years ago. He explained it like this:
The each turbine has a 3 phase alternator that generates variable frequency AC. The AC is rectified into DC and fed to an inverter. The inverter converts it to 600(?) volt 3 phase 60 hz AC with the AC synchronized precisely to the grid. The 60 hz AC then goes to a step-up transformer at the base of each turbine. There it is stepped up to 12.5 KV then sent via underground cable to the wind farm's central switchyard which is connected to the local grid.
There is a complex automatic control system on each turbine - also a SCADA (central control) system for the entire farm - that regulates each individual turbine's RPM and alternator loading to maximize total system power output. The system also monitors for a wide variety of possible malfunctions (over speed, overload, high temperature, rotor unbalance, etc) and will shutdown/isolate individual turbines as required.
Fascinating technology!
The each turbine has a 3 phase alternator that generates variable frequency AC. The AC is rectified into DC and fed to an inverter. The inverter converts it to 600(?) volt 3 phase 60 hz AC with the AC synchronized precisely to the grid. The 60 hz AC then goes to a step-up transformer at the base of each turbine. There it is stepped up to 12.5 KV then sent via underground cable to the wind farm's central switchyard which is connected to the local grid.
There is a complex automatic control system on each turbine - also a SCADA (central control) system for the entire farm - that regulates each individual turbine's RPM and alternator loading to maximize total system power output. The system also monitors for a wide variety of possible malfunctions (over speed, overload, high temperature, rotor unbalance, etc) and will shutdown/isolate individual turbines as required.
Fascinating technology!
MarkB_MI
Well-known Member
- Location
- Motown USA
Not nearly enough information for anyone to answer your question.
I'm going to take a wild stab in the dark, and guess that what you're really asking is this: "If I have two three-phase wind turbines which run through rectifiers to produce DC, can I connect their DC outputs in parallel?". Well, that probably depends on the manufacturer; I'd check with them. But in general connecting DC power sources in parallel doesn't work real well because whichever source has the higher output voltage will be doing most of the work. That's particularly true with rectified three phase; rectified single phase has a lot of ripple, so two out-of phase single-phase sources will overlap each other and share the load.
My guess is you would be OK if you stuck to a single manufacturer's turbines. jdemaris is the wind power guru, hopefully he has some real-world experience with this.
I'm going to take a wild stab in the dark, and guess that what you're really asking is this: "If I have two three-phase wind turbines which run through rectifiers to produce DC, can I connect their DC outputs in parallel?". Well, that probably depends on the manufacturer; I'd check with them. But in general connecting DC power sources in parallel doesn't work real well because whichever source has the higher output voltage will be doing most of the work. That's particularly true with rectified three phase; rectified single phase has a lot of ripple, so two out-of phase single-phase sources will overlap each other and share the load.
My guess is you would be OK if you stuck to a single manufacturer's turbines. jdemaris is the wind power guru, hopefully he has some real-world experience with this.
I was specifically thinking of home made wind turbines such as designed by the fellow in Scoraig, Scotland and Forcefield in the US. Rectified three phase, not filtered, as close to identical in construction as possible working together on a common bus, in other words distributed small inputs rather than one input. Then further treat the combined output in a remote place as in batteries, inverters, water heating(?)and adjustable loading. But first....
Leo
Leo
Hey Mark, you say "Not nearly enough information for anyone to answer your question"
I will go even further, even WITH more information, I doubt anyone here (unless they have knowledge and expertise using those particular units) can answer his question lol
If we had all the vendors detailed specs and data and had the knowledge and experience to understand them, we "might" have a shot at a "perhaps" correct answer. This topic gets a bit complex for Billy Bob and Bubba and even for engineers and technicians who haven't worked in that field.
I guess if one knew the vendor and specific units they could research and copy and paste their information, but to figure it out on our own takes a bit more expertise.
But heck we all try our best and do what we can which is why I love it here and all the fine gents who contribute. ITS FUN HERE
Take care up North there...
John T
I will go even further, even WITH more information, I doubt anyone here (unless they have knowledge and expertise using those particular units) can answer his question lol
If we had all the vendors detailed specs and data and had the knowledge and experience to understand them, we "might" have a shot at a "perhaps" correct answer. This topic gets a bit complex for Billy Bob and Bubba and even for engineers and technicians who haven't worked in that field.
I guess if one knew the vendor and specific units they could research and copy and paste their information, but to figure it out on our own takes a bit more expertise.
But heck we all try our best and do what we can which is why I love it here and all the fine gents who contribute. ITS FUN HERE
Take care up North there...
John T
While rectified three phase could be smoother then single phase, its still unfiltered as you say with ripples which doesn't sync near as well as say pure DC batteries which many off grid home stored energy systems use. Absent any specs or data Id say generally speaking DC can still be connected in series or parallel and it can "work" but I can just envision imbalance problems. Heck its hard to get good balance even with DC batteries let alone sources with unsynced AC ripple....
AGAIN this is beyond my pay scale and Im NOT experienced in this field and absent detailed specs and data I agree with Mark below that the gents here may not be able to provide a good answer. BUT IM ALL FOR ALTERNATIVE ENERGY AND WISH YOU THE BEST maybe someone here has used such a system and has detailed information and experience with coupling different sources and can help you, sorry I sure cant absent more info.
John T
AGAIN this is beyond my pay scale and Im NOT experienced in this field and absent detailed specs and data I agree with Mark below that the gents here may not be able to provide a good answer. BUT IM ALL FOR ALTERNATIVE ENERGY AND WISH YOU THE BEST maybe someone here has used such a system and has detailed information and experience with coupling different sources and can help you, sorry I sure cant absent more info.
John T
MarkB_MI
Well-known Member
- Location
- Motown USA
When you're dealing with commercial generators, you have a reasonable expectation that there's some degree of voltage regulation, and that the product has been properly engineered and tested to work in the real world. With a homemade turbine, you're pretty much on your own. You might have some luck posting your question to the designer of the system you want to build.
I'd say as long as you're charging a battery bank, as opposed to trying to use raw rectified ac power out of the generator, you can probably get away with paralleling the turbines. When you're charging a battery, there's no current through a generator phase until the phase voltage exceeds the battery voltage. Once the rectifier is forward-biased, the battery essentially becomes a short circuit, and the phase voltage won't rise any higher. I wouldn't expect to get the twice the power out of two paralleled turbine as you could get with a single turbine. The higher the charge voltage the lower the current, and two generators in parallel will charge at a higher voltage than one.
Can you post a web link to the site of the system you're considering?
I'd say as long as you're charging a battery bank, as opposed to trying to use raw rectified ac power out of the generator, you can probably get away with paralleling the turbines. When you're charging a battery, there's no current through a generator phase until the phase voltage exceeds the battery voltage. Once the rectifier is forward-biased, the battery essentially becomes a short circuit, and the phase voltage won't rise any higher. I wouldn't expect to get the twice the power out of two paralleled turbine as you could get with a single turbine. The higher the charge voltage the lower the current, and two generators in parallel will charge at a higher voltage than one.
Can you post a web link to the site of the system you're considering?
Yes, I will/would contact the designer before I started anything. The reasoning behind this approach is that (from what I have read) the higher the turbine above earth the very significant availability of power. The larger the swept area, significant potential for power. However, larger means heavier and better tower which gets costly and the combination is likely more vulnerable to storm damage and much harder to maintain or experiment with. At 79 years, I am not going to climb or crank much! So...how about a fence row with, say multiple 20 feet high (above the cornstalks!)that I could handle the maintenance of...like an orchard keeper)of smaller, less susceptible, moderately small units.
I appreciate the friendly advice and experiences of all, here. I have never been arrested for being too smart...honest. Leo
I appreciate the friendly advice and experiences of all, here. I have never been arrested for being too smart...honest. Leo
Geo-TH,In
Well-known Member
JohnT,
"I will go even further, even WITH more information, I doubt anyone here (unless they have knowledge and expertise using those particular units) can answer his question lol"
Did anyone ask BUBBA? Bet he could answer it, may not be correct, but he would give you an answer.
Wave theory in physics says when a crest of one wave lines up with the trough another wave, you will have destructive interference. So why wouldn't that happen with electricity? I think Edison faced the same issue before he learned he had to sync generators. But I can't remember, it's been a long time since I chatted with Thomas.
"I will go even further, even WITH more information, I doubt anyone here (unless they have knowledge and expertise using those particular units) can answer his question lol"
Did anyone ask BUBBA? Bet he could answer it, may not be correct, but he would give you an answer.
Wave theory in physics says when a crest of one wave lines up with the trough another wave, you will have destructive interference. So why wouldn't that happen with electricity? I think Edison faced the same issue before he learned he had to sync generators. But I can't remember, it's been a long time since I chatted with Thomas.
Geo-TH,In
Well-known Member
Yes it is very fascinating. If one thinks about AC it has to be sync or it would be like putting 2 12v car batteries in series opposing, +12v to another +12v. Output between the 2 negative terminals would be ZERO.
Bet the control systems is very expensive. Definately wouldn't be pratical for the average person.
Bet the control systems is very expensive. Definately wouldn't be pratical for the average person.
MarkB_MI
Well-known Member
- Location
- Motown USA
George, the key thing here is the original poster said "rectified three phase". In other words, DC. The alternator in your car provides rectified three phase. Can you connect two alternators in parallel? Sure, just hook jumper cables between two running vehicles. It's not a great idea, but 99 percent of the time nothing much will happen.
So what are these crests and troughs of which you speak? For RECTIFIED three phase, they are small and occur every 60 degrees of phase. We electrical engineers call them "ripple". Here's the interesting thing: If we shift one alternator 30 degrees with respect to another, we actually have a smoother DC output than if they happen to be perfectly in phase. So having two alternators out of phase is no big deal as long as you're tying together their RECTIFIED outputs.
So what are these crests and troughs of which you speak? For RECTIFIED three phase, they are small and occur every 60 degrees of phase. We electrical engineers call them "ripple". Here's the interesting thing: If we shift one alternator 30 degrees with respect to another, we actually have a smoother DC output than if they happen to be perfectly in phase. So having two alternators out of phase is no big deal as long as you're tying together their RECTIFIED outputs.
Geo-TH,In
Well-known Member
I was going to do an experiment today, using 2 battery chargers, one 6 amp and the other one 15 amp. Put both of them in parallel and then connect to a 12v battery. One charger I was going to plug into a wall outlet, 120vac and 60 hz. The other charger I was going to connect to a portable generator, 120vac, so I could change the engine speed which would change the frequency. My new genny was set at the factory to 65 hz. They said it was set a higher frequency because under load the frequency would come down a little. My generator also came with a built in frequency meter.
Both of the chargers I was going to use are old school, manual, no brain boxes.
However I gave away my old 6 amp charger. That said, it would be very easy to use 2 old school battery chargers to experiment with instead of building 3 phase wind power genny.
I was also going to use a variac, an adjustable transformer, to decrease one of the input voltage going to one of the chargers.
I was expecting to find the charger with a lower input voltage may not add anything to charging the battery. I was also expecting to finding a small beat frequency produced by using 2 different frequencys. Perhaps if I find another old school manual charger, I'll do the experiment and post my findings.
I still want to know if Fred Sanford drank ripple or was it MD 20-20?
Both of the chargers I was going to use are old school, manual, no brain boxes.
However I gave away my old 6 amp charger. That said, it would be very easy to use 2 old school battery chargers to experiment with instead of building 3 phase wind power genny.
I was also going to use a variac, an adjustable transformer, to decrease one of the input voltage going to one of the chargers.
I was expecting to find the charger with a lower input voltage may not add anything to charging the battery. I was also expecting to finding a small beat frequency produced by using 2 different frequencys. Perhaps if I find another old school manual charger, I'll do the experiment and post my findings.
I still want to know if Fred Sanford drank ripple or was it MD 20-20?
buickanddeere
Well-known Member
If these are hobby sized generators are identical and the rectumfied DC is paralleled together . Should not be any particular problems.
You can find info on these DIY alternators by searching Hugh Piggot in Scoraig, Scotland or Forcefield in CO as they supply the design and magnets that are bonded to a revolving plate mounted on a trailer wheel hub near a ring of hand wound coils. Called axial flux design. Hand carved wooden blades. Various sizes, outputs. Leo
MarkB_MI
Well-known Member
- Location
- Motown USA
Well, these seem to be fairly simple, unregulated alternators. I don't think there would be any problem connecting as many as you want in parallel, as long as you have plenty of battery capacity.
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