240vac Auto Alternator conversion

[ElectricFreak]

Has anyone out there ever reworked an auto alternator for 240vac output?

I would like to find someone who can rewind the stator for 240 volt single phase output.

Anyone got any ideas? is this feasable? a bad idea? Would I be better off buying a generator head?

I would like to find a "shop" to do this, because I want multiple identical units.

This is for my geared up 12' wind rotor.

Thanks,

Chris

[Nando]

BAD idea indeed, the alternator will require power to generate the magnetic field for the rotor, this power may run as high as 100 -- 160 watts depending on size of the unit, also the RPM needs to be quite high unless you place a RPM multiplier to produce the 2000+ RPM needed to attain the desired power.

Better calculate the RPM at the desired wind velocity and with the 12 feet mill you have in mind.

Why do you want 240 Volts ?

Nando

[nanotech]

 Why do you want 240 Volts ?  

Possibly in Europe, UK, or Australia?  Would be my guess....  

[ElectricFreak]

Thanks for the info...

I wanted 240vac because it will require less current to cary the same amount of power as a lower voltage. Also I wanted AC because I would like to have the tower some distance from my other equipment.

My only "problem with pmg generators is how do you regulate the output?

I would like to be able to hold a maximum voltage, and increase the amperage as necessary to keep the rotor speed down.

I am somewhat stubborn in the fact that I only want the blades turning a maximum of 500 rpm. My blades have a lot of torque, but very little in rpm range.

Chris

[ElectricFreak]

Also I forgot to mention, I am running a 10:1 gearbox that will step up the shaft speed. and I have a PLC which will be mounted inside the housing to control the generator.

Chris

[WXYZCIENCE]

10:1 increase is far to much for any small design. The torque on the front end will only make it so that everything has to be beefed up. Plus more losses. I have a video of a eggbeater that was rated at 10kw, the primary gear was 6" across gear up 15:1. One of the foil mounting flanges let go and the foil cut all of the guy wires. What a horrible site. This was near Taber Alberta, wind never stops blowing there. My point faster rotor speed slower genny works better all around. I also think the electrical code for higher voltage is different. But if you are set in your direction that's ok, keep posting the results. Joe.

[Nando]

With the PLC you can drive a couple of MosFets to control a couple of resistor ballasts, one in PWM mode 0 to 100 % and the other ON/OFF.

You will be able to maintain the Voltage output stable.

What is the distance between the turbine and the load ?.

How much power ?.

Nando

[Nando]

May be not, may to send the power some distance, I prefer to ask than to guess.

Nando

[ElectricFreak]

Hi all, and I appreciate all the input.

I might as well spell out my plans so you can ponder them.

I already have the gearbox, and I do not plan on using a tall tower.

at my test site(my house)the load is close, like 25 feet, but after the bugs are worked out I have a site that is practically a mountian top, so I can put the thing low, and make it very sturdy.

My rotor has 9 blades, and is a downwind design, and was made with maximum torque in mind, not speed. My "target" rpm is 500, the rotor will handle more, but it should become very ineffecient.

the gearbox will provide the mounting point for the rotor, as it has a 1.5" shaft.

The mount will include at least a couple sets of sliprings.

Good or Bad, All the above items I am already decided on. I would have prefered a lower gear ratio, but this is what I have and I may be forced to change this later.

I am still not set on the method of power production.

I really do love magnets, but I cannot figure out how to use them with a very wide powerband generator. A large pm generator has too much drag at low wind, and a small one will not provide enough drag in high winds. clutches might work but I am not thrilled with the idea.

a generator head unit would be the easiest, but they are not cheap, and unless I butcher one I doubt it will do what I want very well.

I am toying with the idea of using several GM alternator rotors on 1 shaft, and custom mounting the field coils. With this setup 1 rotor could be energized, and when the PLC determines it is at maximum amps, and the RPM is still climbing the next one would be energized.

A stepped generator of sorts....

This way the drag/load can be adjusted to keep the rotor speed where it works best.

The excess drag could be cut down to brushes, and residual magnetism in the rotors when wind is very low.

Am I forgetting something here?

It might turn out to be a major failure, but at this point, I still want to try.

I am still unsure about how to get single phase out of an alternator, without rewinding it.... is it possible?

Also, I prefer 240vac because it is common here, and it will travel with minimal loss.

Chris

[commanda]

If I might humbly suggest you hang out here for a while and read all you can. There are many knowledgeable people on here who have built very successful windmills quite simply.

A few quick pointers;

Open circuit output voltage of an alternator is proportional to rpm. Saying you want 240 volts is superfluous.

3 phase is more efficient (much) than single phase.

Hi-voltage transmission is preferred for higher powers & longer distances. You can use transformers at the receiving end to convert the voltage back down. I have done some work on this using the Fisher & Paykel smartdrive motors; have a look in my diary.

Don't waste your time with car alternators.

Sell your gearbox on ebay, use the money to buy some neo magnets & magnet wire.

Amanda

[stevesteve]

Chris,

You might be in an area where 240V is common and yes you might well be able to get higher voltages for transmission but you would have to be very careful about controlling the frequency of your output if you were thinking of using it directly.

There is a neat trick which envolves driving a mains voltage AC induction motor at just over it's rated speed to generate mains voltage try 'Google search the board' for 'grid tie induction'. I have not read enough to understand this myself yet but it might be what you need. I'm not quite clear if 500rpm is before or after the 10:1 gearbox?

Any comments anyone, might this be a way forward for Chris with what he has got there?

[bob g]

to answer your primary question , can that stator be rewound to produce 220 vac single phase?

yes

a couple of years ago, i rewound a jb2600 leece neville stator, i don't remember the specific wire size or turn count, but i packed the slots full and set it up as a single phase machine

at 600 rpm it produced 120vac at 60 hz, open voltage

at 1200rpm it produced 240 vac at 120 hz open voltage

at 2400 it produced 480 volts at 240 hz open voltage.

as i said i dont remember the wire size, but i seem to remember that current capacity (ampacity) of the wire was around 7 amps.

the thought was to produce high voltage 120 vac to transfer distance and step down with a battery charger to charge batteries, never got around to applying it yet.

it takes some serious torque to drive it with an angle grinder attached,(about a 4amp load at 110 volts.

also i should note that the rotor draw is around 4 to 5 amps on these alternators

was an interesting experiment, but not sure of a practical application for it yet.

bob g

[terry5732]

I applaud your approach. It seems that many here are stuck in box on how to do things. AC production and transmission are now, as they were 100 years ago, the way to go. Many here are trying to get the most power from the smallest machine. If you have a place for a machine with large power gathering you can accept many inefficiencies. Obviously anyone with 40 acres has a HUGE amount of power in the wind over it.  If you are stuck to 15 square feet of swept area that's another story. You have the luxury of excess power and can therefore do more with it.

You don't want something as tiny as an auto alternator. You can produce with an induction motor using a voltage controller on the field to give you your relatively constant output AC voltage. The power for the field can come from the excess power you are producing via capacitors. If you are driving a 10 Amp induction motor at about it's rated speed you will get about 10 Amps out with the proper excitement of the field. You need to know how much horsepower you can get out of your gearbox and find a 240 V induction motor of about that HP. Then google "squirrel cage motor generator conversion" or something like that.

Funny how no one ever figures into their efficiencies how lossy battery charging is.

[kitno455]

"Funny how no one ever figures into their efficiencies how lossy battery charging is."

my uncle used to say- "Never say 'everyone' or 'no-one', cause there is always 'some-one'".

if you read the board here, you will find lots of folks that take battery efficiency into account, you just failed to notice.

allan

[kitno455]

why are you so hung up on 240? why not 300 or 400? you have to worry at some point about the insulation in your coils, but i have seen good wire rated at 600V.

are you planning to drive loads directly off of the line, without batteries? if so, voltage is not your only problem, you will have to get the Hz right.

also- i dont understand why your prop becomes less efficient at higher rpms? if you choke the thing down with more gens coming online, wont that make you less efficient?

all in all, i think letting the gen follow the wind speed makes more sense...

oh- and if you dont use mags, what will you use to provide excitation of the field? the grid, batteries?

allan

[WXYZCIENCE]

efficiencies how lossy battery charging is.
Lots of people think that power is the stuff you get out of a small thing on the wall of their house. We on this site FULLY understand the losses of a battery. There is many ways of doing something. Battery charging 12to48 volt systems are time tested systems. We encourage anyone who will experiment with new tech. But when I turn on the light in my shop it works every-time, off grid, for years. If someone comes up with a REAL new way of doing thing we are the first to accept it. Joe.

[ElectricFreak]

Hi all,

I started this topic, because I want to find a generator that I can use with the following characterstics.

1. : it needs to put out AC - frequency not important.
   
2. : I would like it to reach a set voltage early, and stay there via regulation.
   
3. : I would like to be able to adjust output amperage as a method of speed control.
   
   

Can we please focus on these goals?

All generators have compromises, but these are my goals.

I can put any regulation required in a PLC, but I am looking for a basic model "theory" to work with.

does anyone think I could do this with a commercial generator head, and some rework?

Maybe I am dreaming, but "it's my dream"

Chris

 

[WXYZCIENCE]

Get an old 240v gas powered alternator, easy to find with a burnt engine. With your gearbox you can achieve the rpms you need. I made one like this to run my 240 volt well pump. Works well. Joe.

[ElectricFreak]

Joe,

can you give me a make/model or brand?

I have never heard of one before.

Thanks,

Chris

 

[kitno455]

uhh- try going to the hardware store?

allan

[zubbly]

hello ElectricFreak!

my 2 cents worth.

if you make a pm alternator, you basically will not be able to control the voltage. it is tied to the rpm.

i think your auto alternator may be a good idea. i have salvaged a few "leese nevil" large truck alternators, 130-160 amp units. most of these units do not have any slip rings because the excitation coil is non rotational. i think you could get away without any gear box if you have the stator rewound. the new stator rewind data can be based on a few tests with the original winding. as in any design, there are always losses, and if you could eliminate the gear box, it would greatly help to offset the watts lost to excite the coil. as your unit would vary in rpm, your control could vary the excitation voltage to maintain whatever output voltage you wish (within reason). i "think" this would give you what you are looking for.

actually, many small gas powered alternators work on the same principle with an electronic regulator. as load is applied, your regulator increases excitation to maintain voltage while your rpm shifts down somewhat and current goes up.

sounds like an interesting project and i think can be done. just wondering if an existing regulator could be adapted with the addition of a few more electronics. (electronics is not my field so can't help there)

just to suggest for an auto alternator rewind:  belt drive the alternator at a known rpm, excite field with whatever voltage you know your system will be using, take output voltage reading of alternator.  the voltage you want, divided by the voltage you got in bench test, times the number of turns per coil of original winding will give you the number of new turns needed for the voltage you want. original conncetion must be maintained and wire size will have to be adjusted smaller to be able to fit all the new turns into the stator slots.  if you give a rewind shop this info, they will be able to perform the rewind for you.

good luck and let us know how it works out!

zubbly

[Goose]

Zubbly,

What about rewinding the stator for single phase?  is this possible, and if it is can you explain how?

thanks

[zubbly]

hi Goose!

yes of coarse, it can be wound single phase.

assuming we are going to use the existing rotor and field coil excitation. the same number of poles would then have to be the same.

the auto alternator is now basically wound with 3 seperate 1 phase windings. the 3 windings are connected for either star or delta. most often the connection is delta.

you would use the same procedure as my first reply, only measure the voltage from one phase and make the same calculations.

but here is why i do not like it. you would be using the same coil spans (usually 1-4) in those alternators, and you would basically be wasting 2/3 of the stator.

what i suggest if single phase output is what you need to use: lets assume you are after 120 volt single phase, 60 hertz.  i would do the pre testing as i mentioned before, and then calculate the 3 phase winding for 208 volt 3 phase 1 star connection @ 450 rpm for 16 pole , 600 rpm for 12 pole. this will give you the 60 hertz.

in many north american 3 phase 208 volt 4 wire systems, single phase 120 volt is derived from connecting from one output line and from connecting to the star point of the 3 phase. when you do this, you get 58% of the line voltage (120 volt). you would then distribute your loads equaly from the 3 lines and the star point.

to have a true single phase winding and to make more use of the stator, you would have to construct a new rotor with les poles and run it faster.  the best way to make use of the stator is really to keep the 3 phase winding and use it as i mentioned with the 4 wire system. this way you will have its full potential

hope that helps!  

zubbly

[WXYZCIENCE]

The one I used is a McCulloch. I can't remember the model. It was in a big round yellow case. Nice thing about it is that it had two coils I just put them in series and I got 240 volts ac. The one I used was on a 5 hp brigs, the problem with this model was that people used to drop them bending the shaft. They are permanent magnet dual rotor, heavy flywheel. It produces 240 volts 7.5 amps. I have it hooked up to my deep 3/4 hp well pump. I drive it with a 36v dc motor. 1900 watts dc, to 1600watts ac. pretty hefty losses, but it is the only thing that will start the pump. And in 3 min. the tank is full. It produces perfect 60 hz ac wave at 3600 rpm. Joe.

[oztules]

84% conversion is not to shabby for pure sinewave output, that starts an induction motor....and power to spare.  

........oztules