5kw Poncelet Wheel Project

[frackers]

Off topic - I have 10+ walnut trees. How do you get the husks off the shells? Do you wash them after you remove the outer husks?

The ideal is to leave the nuts until they drop out of the husk with the husk still attached to the tree. No shaking and hope for not too much wind and rain that knocks them down whole (but a bit of wind + rain helps shift a few 'stuck' nuts). Another disappointing year - only 350kg which is miserable for 200 trees, I was hoping for twice that!

Any still with the husk on can be easily striped (if not too many) by scuffing them with a boot on the grass. We wash after removing the husk as the main purpose is to remove the fine threads under the husk that go mouldy if left - hence the road sweeping brush as a part of the washer design.

[skid]

Things have been running pretty well up to now. The weather cooled off and river flows dropped. When I went to adjust the waterwheel height it was out of the water. As I lowered it into the water it turned very slowly and erratically.

I pulled the wheel up and brought it onto the riverbank. It was very difficult to spin the wheel. I disconnected the belts and the wheel spun freely. I went to spin the generator and it would turn a bit, then resist turning, then turn a bit more, then resist turning. I believe this is called "cogging".

It is a PM generator and always spun freely before. I disconnected the leads and the issue is still there. The bearings are fine.

Anybody have an idea as to what happened and how to repair this issue?

[hiker]

Short in armature,,? Bent shaft,,? Worn brushes,,? Bearing binding,,? Time for a tear down,,

[SparWeb]

Happy new year, skid.

I had something similar happen to my wind turbine when one of the rectifiers shorted.  It was barely turning in a strong wind. 
At the time, I suspected something wrong mechanically, but after some troubleshooting on the ground I found the problem measuring voltage drop across the rectifier terminals.

PS. good to hear the bearings are still working well, after all the effort you gave them.

[skid]

Short in armature,,? Bent shaft,,? Worn brushes,,? Bearing binding,,? Time for a tear down,,

I'm not sure about the armature, but the shaft isn't bent, it doesn't have brushes as far as I know (I'm no expert on these), and the bearings seem tight and fine.

Happy new year, skid.

I had something similar happen to my wind turbine when one of the rectifiers shorted.  It was barely turning in a strong wind. 
At the time, I suspected something wrong mechanically, but after some troubleshooting on the ground I found the problem measuring voltage drop across the rectifier terminals.

PS. good to hear the bearings are still working well, after all the effort you gave them.

I disconnected the generator from the power cable and the problem is still there. I'm just very curious as to why it would start doing cogging like this . It turns easy for a few degrees, then gets really difficult for a few degrees, and then turns easy again and so on...

[SparWeb]

Picked up my generator yesterday. 385kg, 7.5Kw, 50rpm permanent magnet. 850 pounds! I'll start fabbing up the mounts and the rest of the cantilever arm soon, as I have most of the material on hand now. Weather is beautiful outside on the west coast right now...My grass needs cutting already!

I went back in time (4 years!!) to refresh my memory.
3 phase, probably wired in Delta?  Do you still have the original specs for it, such as resistance across phases?
My fear is a shorted winding.  This can happen if the insulation on the wire breaks down or something gets inside and contaminates it.

[Mary B]

Yup shorted winding on one of the poles... motor shop may be able to rebuild... might get lucky and it is just a short in the wires coming off the winding...

[skid]

Would water cause this? When I opened the electrical box to get at the terminations some water poured out. It may be possible that some got into the generator windings. We have had non-stop rain here for a while.

[SparWeb]

Where's the emoji for "sinking feeling in the pit of my stomach"

Hoping for the best, Skid.

Best case scenario: no sign of water inside the motor body and a simple bad phase connection found while the body is open.

Next-best case: signs of water in the body, and then the generator needs to be opened, cleaned, dried, core removed, re-varnished, baked, core installed, re-tested (not necessarily in that order) ...and it may pass the hi-pot test.  If not, it will need a re-wind while the core is out.

Worst case: corrosion between the core laminations.

[skid]

I should have mentioned I had 2 ground fault alarms on my just inverter prior to this. They reset each time.

[Frank S]

 With it disconnected a short in the wiring would not show a tight spot. this sounds more like grit in the bearings or a ball bearing going bad often they can be turned a little one way or the other really easy then hit the bad spot and be more difficult. It sounds to me like they may have gone dry and galled if the shaft as you say is not bent. or there is nothing obstructing the rotor  or the fan on the end.

[skid]

I contacted the manufacturer and this was their response:

I think there might be the short circuit.
When you disconnect the generator with the rectifier, is the torque still big?
Is the insulation between the live wire and the generator casing OK?
____________________________________

[skid]

I took the end caps and bearing housings off the ends of the generator. There was definitely water inside. I sat it in front of the wood stove in the shop for a few days and dried it out. I then took some electrical contact cleaner and cleaned all the rust and dust out of the places I could get to.  I re-assembled it and now it turns normally, so it looks like water was the culprit.

I will now dis-assemble it and re-assemble with the intention of completely sealing it. There were no lip seals in the bearing caps, so that was one area of water entry. They didn't leave enough room in the bearing caps to machine it for a lip seal, so I'll try to cap the non-drive end, and somehow shield/protect the drive end from water entry.

The electrical box was the main leaking point as it had a couple of cheap rubber gaskets that didn't seal very well. I'll silicone everything now.

Lastly, I'll build a roof  to cover the generator from rain, which I should have done from the get go. Thank goodness I don't have to spring for a new generator!

[SparWeb]

Drain hole in the motor case?
Slinger seal?

[MattM]

There is always the possibility the source of moisture is when the weather warms and condensate occurs in the cool metal housing and whatnot.

[ontfarmer]

MattM    That has been my thoughts! 

[skid]

I repacked the bearings with grease, silicone'd everything up and re-assembled the generator. It spun freely a couple times, and then started cogging again. Looks like it is screwed.

I wonder if there is anything salvageable inside (magnets, etc.) or is it just scrap metal now?

I've priced out a new one, which is cheaper than trying to rebuild. I'll go with something smaller in the 3kw range as well.

[SparWeb]

This generator?
https://www.fieldlines.com/index.php/topic,148325.msg1032567.html#msg1032567



Can you provide a photo of the data plate?

[MagnetJuice]

Skid, you mentioned earlier that you would like to build your own direct drive generator.

I plugged some numbers and even at 10 RPM it is doable. But not using the existing pulley to mount the magnets, there is not enough flat area on that pulley. The generator would require 2 large steel disks for the rotors and have to be attached to the wheel shaft. I think that the complete generator would weigh less than the 600 Lbs. pulley that you have now. I would need to do some calculations to verify the weight.

Ed

[mbouwer]

you would like to build your own direct drive generator

That sounds like music in my ears.

Rinus

[MagnetJuice]

Skid, here are some preliminary figures in case that you are interested in building your own generator.

It would be a normal 3-phase axial flux, with 44 magnets per rotor and 33 coils on the stator sandwiched between the 2 rotors. Each coil will have 80 turns of 16 Ga. wire, (or maybe 17 Ga.) This alternator can produce 3.5 KW or more if your wheel can provide that much power. Turning at 24 RPM, it will output about 135 VDC. I think that your Aurora Inverter would be happy with that voltage. If you need higher voltage, then the number of turns in the coils has to go up.

At first I thought that it would be possible to attach the alternator directly to the shaft of the wheel, but after looking at the videos, the maximum speed that I saw was about 9 RPM. If you dip the wheel lower into the water, you gain torque but loose RPM. An alternator that can output 3.5 KW at 9 RPM would be a monster. I chose 24 RPM so that you can have a sheave of approximately 15” on the alternator shaft. That will give you about 4 to 1 ratio and would minimize belt slippage.

I chose ceramic magnets because they will not corrode. They cost about $4 each. Another choice could be to use Samarium Cobalt magnets, but they cost about 5 times more than ceramic. On the other hand, Samarium Cobalt are more powerful, so the alternator would be smaller and the cost of the copper wire would be less. Neodymium magnets? They are very powerful and the cost is reasonable, but until someone comes up with a way to protect them from corrosion, they are out of the question. Especially considering the wet environment where your equipment is located.

If you decide to build this, I am confident that with help from the wizards on this Forum, you would end up with a nice generator.

Here is a rough drawing to give you an idea about size.

[joestue]

i would rewind the generator before trying that.

[MagnetJuice]

I don't know how much it would cost him to rewind the generator. I was talking to the owner of a motor repair shop and he said that he doesn't do rewinds anymore because people can buy a new motor for less that it would cost to rewind it. He sold me all his magnet wire at cost.

I see some advantages of building this axial generator.

1-   He can use a large axle for the generator with roller bearings that can take the heavy load of those belts pulling on them.

2-   The large diameter heavy rotors will act as a flywheel to smooth any variation on the rotation of the water wheel, reducing the voltage swings.

3-   The output of the generator can be set between 2Kw and 4.5Kw by adjusting the air gap. That way the generator output can be set to match the increase in output from any modifications that he makes to the water wheel in the future.

4-   There is no need to protect it from the rain, because the magnets don't rust. The steel can be coated with POR 15 like the other parts are.

5-   The stator can be made using 15 Ga. wire. That's good for 6Kw. The coils will be totally enclosed in resin. Water will not damage them like it did to the current generator.

6-   And the best part is that it will give Skid a new set of skills and the pleasure of doing it himself.

Another thing, by using large roller bearings on the generator axle, the tension on the belts can be increased to eliminate slipping. In that case he could turn the end of the axle and use the sheave that is on the generator now. That will bring the generator speed to about 40 RPM instead of 24. That will produce more voltage.

As a bonus, all of us in the Forum will see the construction and operation of a large low RPM alternator.

Ed

[skid]

Magnetic Juice,
Thanks for spending the time to lay that out! I'd love to have a generator as you've described!

Unfortunately I just don't have the time or knowledge to build my own generator. I can get a new generator for around $2kUSD which is probably the route I'll go. I probably couldn't build my own for that kind of money.

[MagnetJuice]

I did these calculations because you had said that you would like to build your own. And since the generator that you had failed, I wanted to show that it is possible to build your own, especially with your talent and mechanical skills. I just wanted to give you some options in case that you wanted to go that route.

Here is some additional information:

The cost for the magnets would be about $480 and about $825 for the copper wire. The weight of the magnets is about 185 Lbs. and the copper wire (coils) about 66 Lbs. The steel rotors are about 117 Lbs. each and about 15 Lbs. for the vinyl ester resin. The complete generator with the shaft and bearings would weight about 530 Lbs.

The harder part about building this would be winding the coils. I would not attempt to wind these size coils myself. There are businesses that custom build the coils for you according to your specifications. Here is one that can do the work:

http://www.production-solution.com

I am sure there are many other businesses that do that kind of work.

Here is a picture of a low RPM alternator that a Company in Vancouver, (Mermaid Power) is using to generate power from the up and down motion of the waves. As far as I know they are still at the experimental level stage.
 
.


The website is:
https://www.neptunewave.ca
 
That generator has 40 magnets and 30 coils. The rotors are 40 inches in diameter and produces 240 Volts at 47 RPM. At one time he had it for sale on the Hugh Piggott Blog, but then he decided to keep it. He claims that it could produce 6 Kw under ideal conditions. The one I suggested is about 48 inches. I calculated that for 24 RPM, but it could be made smaller if it could rotate at 40 RPM.

Like I said before, I'm not trying to convince you of anything, just giving you some options so you can make an informed decision.

By the way, I saw that video that you posted of the wind storm last December. Did it damage any of your wheel or equipment? I felt that storm here but it wasn't that bad in my area. It only disturbed my sleep and sent some trash cans flying.

If you have any questions just ask. By now you know that there are people here that have built their own generators and know their stuff. Not me, I just have a little bit of head knowledge. Soon I'll be building my own generator, but not a big one like this.
 
Ed

[mbouwer]

Impressive nice piece of work.

@MagnetJuice,
Are you going to use a laminated iron core?

[MagnetJuice]

Not iron cores at this time mbouwer. Only simple air core axial flux alternators.

I believe that iron cores are better adapted for radial flux alternators, where the parts can be configured in a way to minimize or eliminate cogging.

In an axial flux, the magnetic flux that the coils are exposed to can be increased simply by having a steel plate on the other side of the stator, and that steel plate is rotating with the rotor that has the magnets. No cogging that way.

Better yet, have magnets on both steel plates, and if you want a stronger magnetic field, make the coils as thin as possible. That way the two magnets will be closer to each other, intensifying the magnetic field.

What I described there is the typical “tried and true” axial flux alternator that has been around for a long time.

I believe in simplicity an ease of construction. That way more people feel inclined to build their own and start experimenting and generating a little bit of their own power.

Different people like different things and that is perfectly OK with me.

Ed

[MattM]

The copper coils appear to float off the outer ring.  This makes me suspect the torsion on the coils - which should equal the forces acting on the coils - is low enough the steel rotor holding the magnets could be substantially lighter.

[MagnetJuice]

I understand what you are saying, but I think that the stator was not finished yet in that picture.

I suspect that another ring, similar to the one outside, was placed on the inside to lock those coils in place. Even low power ceramic magnets could give those coils a good shaking.

[DanG]

https://vimeo.com/139096214  <--- geehaw, in motion & catchy tune

[keithturtle]

What did it do with a load wired in?

[MagnetJuice]

I haven't been able to find any output data on this alternator yet.



That could be open volts readings, with no load connected. One thing I noticed is that the readings are AC Volts and for only two of the 3 phases. After that 239 Average voltage from two phases is converted to three phases and rectified, we are talking about 650 Volts dc. Very impressive.

                                                          * EDIT *

Correction:
I made a mistake in the above calculations.

I assumed that the 239 volts were Average volts, but they are Phase-to-Phase volts.
Average voltage for one phase would be 138 Volts. That would translate to about 375 Volts dc.

[joestue]

https://vimeo.com/139096214  <--- geehaw, in motion & catchy tune

so you've got some kind of overrunning clutch somewhere that rectifies the reversing motion right?

i see lots of chains.. why not gear it up another 10 times and use a generator 1/10th the size?