Adjustable magnet alternator

[Harold in CR]

 Bought some bar magnets with a fin on each side. I want to build a rotor using 5 blank plates from round electrical junction boxes, for an automotive alternator housing. Do the plates need to be insulated from each other, like laminations of a wound rotor ? They will be welded to the steel shaft. I couldn't get a stainless shaft short enough to play with at a reasonable price. The plates will have grooves for the magnets and slots in the inside edges of the grooves to hold he magnets.

 On ebay, a similar rotor goes for $150.00 or so. I can play pretty cheaply. 

 My idea is to mount the rotor in a fixed position using pillow block or other similar shaft bearings, and slide the alternator housing along the rotor, to increase or decrease the magnetic flux, similar to a regulator controlled alternator.

 IF I can get this to work, I'm thinking it would be possible to match the flow of water from the turbine, so the lesser flow won't stall the rotor. I have from 20GPM to maybe 2000GPM, depending on the rains, so, I want to use the lowest flow rating as a minimum to prevent stalling, and use whatever I can capture from excessive rains.

Clear as mud    I would appreciate any opinions, but, I will still build this thing, so, any positive thinking ideas are welcome.

 I'm retired, so, messing with this nights instead of ogling the "tube" is what I am planning.

[jlt]

A water turbine speed  doesn't change that much ,with different size nozzles. The load put on it has more effect .

I built a pelton wheel Using a water pump that came off a3.5 chev engine. It already has a shaft that has bearings and a water seal .

I only have 7gpm to work with so I only get about 3.5 amps  That wasn't much . and I use the water for watering lawns and gardens.

mine used a two pole permanent magnet motor. And was  attached to the pelton with a love joy coupling 

I could not visualize what you are trying to do. and all the junction boxes I have seen are only about 3" in size.

[Flux]

I take it that the junction box discs are to form a core for a pm rotor for the car alternator.
Not really sure about your magnets but if they produce poles NSNS and have the correct number of poles to suit the alternator then it should work You needn't make any specific attempt to insulate the discs, The flux ripple there will be tiny and even a solid core will be ok.

With hydro make sure the magnets are held strongly as the speed will most likely be fairly high.

Sliding the rotor will give you a bit of control and may be beneficial as long as the winding is a reasonable match. If it matches full flow when the rotor is fully in then sliding it should bring you out of stall when flow drops. You seem to have a wide range of flow, I don't know how far you can take this but it is worth a try.

Flux

[Harold in CR]

 I'm not very good at explaining things, but, Flux figured out exactly what I am trying to accomplish.

 The water, if left at a fixed nozzle size, could very well stall the rotor, if I can't match the electrical load to the rpm's/torque of the turbine. If just pumping water, that would not matter so much. Your supply of pumped water for usage would just slow to a trickle.

 I got the sliding Alternator idea from watching a video of a Japanese hubmotor, being slowed and raising RPM's by sliding the stator in and out of the permanent magnet.

 Also, I believe Harris had done some experimenting of moving/reducing the effects of magnetic flux in his Pelton systems.

I bought the blank covers, and the junction boxes do come in 3" and 4" round types. I will center drill them and weld them to the shaft. Then, I will rig a way to spin the assembly, and use my angle grinder to slowly grind them down to final dia. Then, I will grind rectanular openings for the magnets, and will need to cut a slot in each opening edge, to press the magnets into. This will prevent them from flying off the rotor.
 The magnets are polarized through the thickness, so, I can just alternate each magnet to get the NSNSNS 6 pole rotor. The alternator has 6 N pole claw fingers and 6 S pole claw fingers. That's why I bought 7 magnets, allowing for screwing up one of them, somehow. 

 In my build thread, I explained how I had maximum water in a pair of 4" pies, running to the turbine. This will be max possibly 100 GPM potential of my system, and a 20GPM will be the minimum of my system. I have 26' of head once I get the weir constructed.

 The original rotor I will leave original, so, I can play with each set up and get readings of outputs and RPM's, so I can try to figure out how to make the governing mechanism to move the Alternator housing.

The stator in the Alternator is .75" thick, so, I bought .75" long Neodymium N45 magnets.  There will not be a lot of movement of the stator in this design, so, it will be a fine tuning type design, hopefully.

The Alternator is listed as a 25A rating, as far as I could find searching. It's a Denso from a Toyota, that I bought rebuilt from an Alternator repair shop near where I used to live. We kept burning out the external regulator, so, we switched to a 60A 1 wire Delco Alternator on our sawmill. That worked well, and, I had the Alternator laying on a shelf.
 Thanks to both responders, especially Flux, for explaining what I thought I had figured out. I was not sure the idea had merit.

 I will add a link to this thread in my build thread, unless an admin wants to move this thread into my build thread.

[hydrosun]

I think you should use 12 magnets (6 north + 6 south) to match the stator coils.
Harris uses 24 magnets. His unit has one on each side of 12  steel bars that transfer the flux to the stator. When both magnets are aligned thw same direction the bar has the strongest flux and when the magnets are slid past that point the magnets start to oppose each pair and the flux decreases. That continues until the magets completely oppose and cancel out all magnetic flux. I spent several days last week experimenting with stronger larger magnets in my harris to increase tge maximum output. I use an Outback maximum power point tracker so the voltage increases to unload the turbine to compensate at lower water flows. So I don't have to physically move the magnets anymore.
You system is more like the alternator on the esd hydro. It has a pancake holding the magnets above the flat stator.  Two nuts on the threaded shaft push it closer or away to vary the magnetic strength.
Chris

[Harold in CR]

 I had wondered about using more magnets, then remembered the ones available on ebay that have 7 magnets for the Delco Automotive Alternators. I can always get more of what I bought, so, I will proceed with the 6 for now, and add more as I do the experiments.

 The one thing that bothers me, is, The Piggott Axial Flux that people use on wind turbines, has an even/odd number of magnets ratio to coils. Might that be in relation to the way the coils are laid flat ?

 I was simply following the rotor claw count on the Denso Alternator rotor.

 Have you done any rewinding on your Alternator, Chris ?  Thanks for jumping in here. I still might learn something from you guys. 

 Harold

[Flux]

Yes you need a 12 pole rotor. The claw has 6 N poles and 6 S poles. You need 12 magnets with width about that of the claws near their mid points.

Car alternators tend to be 12 or more, if yours has 6 claws per side it is 12 pole.

Don't worry about comparing with the Piggott type alternator, slotted core machines are not wound that way. All the information you need is 12 poles of sufficent width to cover 2/3 of the circumference ( leaving 1/3 as gaps between magnets). This figure is not very critical and even if the magnets are a bit wide and nearly touch it will be ok.

If you only have 6 magnets and they are suitable width you could try with the 6 magnets all being N pole out and in the gaps where the S pole ones ought to be you can use mild steel blanks of the same size to return the flux.

Having a buck converter for the matching as Hydrosun suggeats is a nice convenient way and simpler mechanically but the sliding rotor will work.

Flux

[Harold in CR]

Looks like I need to order more magnets in a couple of weeks.  Just wondering why the ones for ale have 7 magnets ? Could be the stator has been rewound ?

 Thanks for the additional input.

 Harold

[Flux]

7 pioles is not a viable option but if used with alternate mild steel blocks then you could make a 14 pole rotor, which I believe is common on car alternators ( 7 claws per side).

If you can get a stainless shaft and retain ther claws you can fit magnets between the claws all facing the same way. The ideal is a donut shape magnet but rectangular blocks spaced round would do..

It is highly unlikely that a simple machine such as a car alternator can be wound for a different pole number, there just won't be enough slots to use a close alternative.

Your 12 pole machine almost certainly has 36 slots. 14 poles would have 42 and 16 pole ( 8 claws) would need 48..

Flux

[Harold in CR]

 Flux
 I did a Delco Alternator a couple of years ago, using 2 ring magnets that are inside the rotor claws. I used the original steel shaft, and spun it up on my chucked wood lathe. I got V readings, but, this was to play with a wind turbine, and, our trees grew too high to put a turbine up, so the Alternator sits in a plastic zip lock bag on the shelf.

One Randy Draper was a prominent poster on an R/C forum. He had all the answers, until some educated guys started questioning him, and he dropped out of the thread. This is where I got some mislead info, so, I shelved the Delco. Still might do the new SS shaft and try it on a wind turbine. Trees are getting near harvestable diameters.

 Thanks, Harold

[hydrosun]

I've also wondered about the 7 magnet rotors on the alternators for sale on ebay. If they are 14 coil stators they might be fitting them with an altternative return path for the flux. I reread your description an it sounds like you intended to put tge magnets on it's side to use both the north and south strength. If that is true I think they would tend to cancel each other in that direction. Lay them with one face toward the stator.
I haven't rewound any stators myself. I've bought the different stators from Don Harris or had Jerry Ostermyer at APM hydro rewind them for me. I have a stator I smashed the wires when experimenting wirh different magnets I am toying wirh the idea of rewinding but may just let Jerry do.
Chris

[Harold in CR]

 Chris, no, I'm not standing the magnets on edge. I am laying them flat. They are magnetized through the thickness, so, just turn one over so they are opposing each other. I couldn't find a photo to copy of the ebay ones. They do have raised sections after each magnet, like Flux described I might want to try. They magnets also have a groove on each side, so, slide onto rotor "ears". Mine have the "ears" so, slide into grooves that I need to cut in the rotor.

Might be a photo here. 

 Could you possibly share what the winding configurations were in the stators you had rewound ? I have magnet wire to try with, If I decide to.

 I want to push the AC output from the Alternator, approximately 200 feet to the rectifier and batteries. Can anyone explain how this would be accomplished ?  I have an idea, but, would appreciate hearing from someone, before I post my idea.

[hydrosun]

There is no real advantage to rectifying at the batteries unless you wind the alternator for higher voltage and then use transformers near the battery and then rectify. The amount of wire to transfer the power is slightly more at low voltage ac as low voltage dc. The ac voltage rises and falls so part of  the time the voltage is zero so the peak amperage has to be higher so the losses are higher.
Chris

[Harold in CR]

 You really believe I can push roughly 10A at 12V over 200' and charge the batteries ??  I thought that would be very difficult without using #2 Aluminum or so ??  I know I have to reach a happy medium.  What size wire would you recommend, Chris ?

 Harold

[hydrosun]

What I was trying to say is unless you go to a higher voltage and transform at the batteries (by either ac tranaformers or dc to dc switcher)  you will still need larger wire. With 12 volt and 10 amps over 200 feet I would use 4ga copper or 2 ga aluminum for 1 volt drop (10watts). Using 6 ga copper 4 ga aluminum would lose 16 watts. 10 ga copper would drop 4 volts (40 watts). You can parallel more wire to cut losses. If all you have is small wire you can use that while you experiment.  You may not produce as many amps as you think. So don't spend alot of money on large wire until you are sure it is worth while to cut voltage drop. Then if you want to throw money at it you could get a mppt controller 
Chris

[Harold in CR]

 From what I have read, and, possibly not completely understood ??, is, with the rectifiers not at the turbine location, the alternators will produce AC voltage. I had thought that would be much easier to push a fair distance without much line losses .  Am I not seeing this correctly ?

 When I was a journeyman Lineman for a power company, we didn't have exceptionally long secondary runs, but, increasing the voltage from 4800 to 12,500 used much smaller wires.

 In 'Nam, I ran the generator shop for the Battalion area. I ran all the wires and had a 60KW Generator. Ran all 120V stuff a LONG distance and did have line losses. Biggest problem was controlling frequency. at 59.5 cycles, the tape players would growl and moan. Sounded like the voices were people dying.    I did have larger gauge wire, and bigger loads,so, it all worked out, until someone would be smarter than me and hook up stuff I didn't authorize. Then, I had to track that down and take it away, until I found a way to reroute stuff to accommodate the troops. It took a lot of thinking to make the whole system function.

 Might this be a reason to rewind the stator to a higher Voltage to be ale to push on smaller gauge wires ?  IF it ever stops raining, I will measure exactly the run distance and then figure what I will need to do.

 Thanks for the info, Chris.  Harold

[hydrosun]

AC or Dc doesn't matter much, it's the higher voltage and lower amperage that allows long distance with smaller wire. 12 volts ac would still need larger wire.  Rewinding is needed to produce the higher voltage but then you need three transformers. The efficiency is low when the output is rectified and charging batteries. The cost and losses in the transformers isn't worth it for 200 feet.  I would just use the larger wire unless you use a mppt to run high voltage dc and let the circuit find the voltage that produced the most power at different water rates.
Chris

[Harold in CR]

 Mppt is something I have no knowledge about. Is there something affordable, not exactly cheap, that I should look for, to try to learn more about them ? This is where I will have the most trouble, finding suitable electronics that are not junk from the start. I do have the making for the Ghurd controller, but, it is more an overcharge/dump controller, I believe? Can't remember, exactly.

 I really appreciate all your input, Chris.

 I'm finding that the brain doesn't function like it used to. I "lose" tools that are right in front of me, go to do something and forget what that something is, etc. Yesterday, I was adding water to our Aquaponics fish tank and forgot about it. Then, I had to drain 50 gallons of valuable plant food, rapidly, so the fish didn't start jumping out of the tank.

 It is getting progressively worse. Hope I don't forget how to fall some trees I need to drop, to saw up some lumber.

[hydrosun]

Mppt are controllers used for solar and can be adapted to hydro systems. A lower cost route to a dc to dc converter is a battery charger that takes 48 volts from the main battery on anelectric golf cart and converts it to 12 volts to run electronics and lights. Also a battery equalizer can make a 4 to 1 ratio between the input at 48 volts and the output at 12 volts. These devices make the conversions but don't allow adjustments to get the best ratio of voltages to produce the most power like a maxmum power tracking circuit. But with movable magnets you can do the adjustments there.
Having said all that you may want to keep it as simple as possible for the highest reliability.   You could use a higher system voltage like 24 volts. I switched to a 24 volt system 15 years ago when I added more power and kept the wire sizes the same.
Chris

[Flux]

Can't add much to what Chris has said. It is voltage that cuts transmission loss. In fact for rectified dc you are better transmitting dc than ac. For the same loss you need one extra cable of the same csa for ac.

Going to 24v will halve ther current and reduce the line loss to 1/4 for the same cable. Transformers work but may cost as much as thicker cable unless you can find something surplus. At least with car type alternators your frequency is quite high and this will reduce transformer costs, but you need to know the frequency and scale the nominal transformer volts in volts.cycle. A 6v transformer designed for 60Hz would handle 12v at 120 Hz.

The buck converter is most efficient and attractive but lacks simplicity. To get a good match it needs to be variable.

Try your matching experiments with a local battery, you will then know what is available. That way you can decide how far it is worth trying to minimise the cable loss.

Flux

[Harold in CR]

 Thanks for the input, guys.

 Looks like I may need to rethink this. I used to be pretty good at estimating distances.  Yesterday, we took the tape to the fence lines which is the shortest route from Turbine to proposed battery location. Comes out to 725 feet of run.    Initially, I wanted to do just from the stream to the batteries. That would have been 560 feet. These hills add up in exact footage compared to line of sight distance.

 I still have 3 solar panels to build and a wind turbine to build and figure out how to get that to catch the wind. We planted trees and they are 60' tall or more, in 8 years of growing.    Nothing good comes easy. 

 I will keep an eye out in the USA for a good deal on wire. Here, it is too expensive. My Son sends a crate down here every 6 months or so. At least, all this info is available to others who might consider what I had to work with, and, the controller info is great.

[hydrosun]

725 feet is completely different from 200 ft. That distance would be better at 48 volts. If you use all your power through the inverter it makes little difference what the batttery voltage is.


 But I've worked with one system that loses over 1/3 of it's power (22volts into 12 volt batteries) on 600 feet of 6 ga aluminum wire. I've tried to make changes but it's complex with two houses with 12 volt systems. It's far from ideal but it works.
Chris

[Harold in CR]

 Another problem has developed. When we got down to the turbine site, I noticed an opening near a tree on the other side of the fence. I crawled through the fence and found a 10' deep hole had been carved into the stream bed and there was NO water running through it. It has BIG boulders down in the bottom. I can hear falling water on another neighbors land, 150 feet downstream from where I was standing.

 There is a 16' drop to where I was going to set the turbine. That was where I get the 26' of head measurement, initially.

 I can't see any way of stopping the erosion, and, it could eat it's way back upstream, to where it ends up on my place ? This is 156' from my fence. 

 Guess I had better get to building the wind turbine and cutting a few trees that are nearly big enough to make sawlogs.  Problem is the cost of a tower. I could saw 30'  6 X 6's and make a 40' angle iron lattice piece that will raise through the 30' section, and make it a free standing tower, and just guy the top 8' down. Damn I hate to have to start climbing again. Getting too damn old. Too easy to get leg cramps.