Star delta comparison

[Jerry]

Hi oztules.

Thanks for injecting your thoughts. As many thought as we can get is good. Like I've allways said, this place is one great think tank.

As per lowering my standard to please what was sugjested to make this a fair race for star. I knew I was giving star a boost (116 turns not 100), a head start, a helping hand but I also knew star would still loose with the sugjested helping  hand, and it did. So the reason I did this was to show even with the helping hand star was still not up to the job.

When efficency is talked about here I think the group is talking about the amount of power that the blade makes and how efficiently the alt turns that spinning force into electricity.

That part I've not thought much about. The part I think about is if I spend $5 on a magnet witch phase scheem extracts the most power. Do I get 11 watts for money spent or do I get 6 watts for the money spent. And if I get 11 watts I'll build the appropriate blade for that power. Or I could spend more money and buy parts to build a larger star alt that makes the same power and use the same larger blade on it.

Or maby stars blade could be a littel smaller but the blade dosn't effect the price tag as much as the wire and magnets and every thing else that goes along with a biger heavyer machine.

And the disusion continues. Need more testers.

                        JK TAS Jerry

[Jerry]

Hi Flux.

Have you a sugjestion on how many turns I should wind to bring stars voltage up to delta/jerry riged on my curent alt?

Its prety easy to wind coils inplace on this motor and the coils will be wound of 18 gage.

I will bring 2 wire per coil out of the motor can for a sires conection to the exsisting star coils.

Delta/jerry riged per coil voltage ac at 500 rpm. 6.729. Stars open voltage ac at 500 rpm 6.149. Looks like just a few turns but I'm not sure the exact count?

Then retesting after that.

                           JK TAS Jerry

[Flux]

Jerry

"You mentioned batteries would be hopeless as a test load". That was a comment to Samoapower I think, he was asking how I held the volts at 20v.

Batteries are fine except that the voltage rises during each test and may not be the same for the next test. I used to use batteries with a charge controller to keep them at constant voltage, the controller takes the same current as the generator and the volts don't change. All I am doing is using the controller direct, the thing is set for a voltage and any increase in current results in more diversion. It is not in any way different from a battery and is not the same as a resistance load.

I am perfectly happy to repeat the tests with a battery but it will have to be nominal 24v.

The only thing is that my coils are stuck on to a piece of 1/8 ply and it vibrates very badly. The tests were done quickly and I expected it to shake apart. If I have to do these tests with a battery and no charge controller I will have to bring it to speed and adjust a load rheostat to bring the volts to the same point each time.

I think I shall have to pot those coils in resin to stiffen it up, otherwise I think it will never survive.

It would be a good idea anyway as it would give more times to take the torque readings, the input figures are obviously not that consistent from the look of the graphs, I wouldn't want to draw much conclusions from those efficiency curves, things don't dart about like that.

Don't know where this will end up, saw your post at first then couldn't find it for ages.

Flux

[Flux]

Thanks

That's great but I wouldn't read too much into it, there is too much scatter in the input readings the efficiencies don't jump about like that.

The basic problem is that all 3 are virtually the same within experimental error.

I can measure the electrical output accurately, but the torque in is much more difficult especially with the thing on the point of destruction with vibration.

Jerry has asked me to repeat the tests into a battery so I will have another go when I have potted that stator and made it more rigid. I think that with it half loaded at any time it may still vibrate to some extent but the plywood goes through resonances at present and this may have some motional feedback electrically as a coil vibrating in a magnetic field must generate a voltage.

A few quick tests seem to have turned into a major project.

Flux

[Flux]

Jerry

I can't remember how many turns you have but you need about another 10%

I am not sure that this is worth doing, it is quite obvious that with that alternator star is never going to produce the same performance.

This thing that you have noticed is something peculiar to simple machines that are far removed from true 3 phase machines. The present one is likely to show much more gain with your method than a converted motor with lots of slots. Winding 3 coils on a stator intended for a low efficiency cheap single phase shaded pole motor is not a true representation of a 3 phase winding.

I would love to have time to try one but I think I should find similar results now I have seen some of your figures.

I think your work may bring considerable benefit to people converting these small things, including ceiling fans and box fans.

More work needs to be done on the input to output power ratio.

It would be interesting to try with a reasonable sized motor conversion using appropriate pole and slot combinations with the equivalent star and delta windings, but I have no time to try that.

For anyone building the air gap machines on the lines suggested by Hugh or Dan I don't think there is any significant difference.

If you depart widely from the dimensions normally used then once again things could be very different.

Don't know where this will land, the comment below yours was meant for SamoaPower.

Flux

[spinner]

hi jerry

find myself wondering if, perhaps, the 9/12 testing should include a setup wherein the genny is connected to batteries which are connected to a load of ? ohms to simulate what a genny is expected to do, in day to day use?

i realize that may introduce some messy variables but, so does the use we put our gennys to.

just a thought

spinner

[SamoaPower]

Fully understand Flux. I've had too much experience reading through "noisy" data to take every data point literally. "Eyeball averaging" is often the name of the game. I would have liked to have done "best fit curves" for your data but would never have done so without your permission - it's your data. I only wanted to consolidate, for clarity over the post, since the data was somewhat separated.

I don't think I can agree with " ... all 3 are virtually the same within experimental error". I don't see a systematic error that would account for the trends indicated. I think there's some real information to be gleaned from these tests. I'm very much interested in efficiency differences of only a few percent. Jerry seems to be more interested in copper costs, which at about $5.00 a pound, is a capital cost that is quickly amortized with a bit of improvement in efficiency. Time needs to be a factor in this sort of analysis.

I appreciate the difficulties with noisy torque measurements. I wonder if you have considered the possibility of measuring electrial input to the prime mover and subtracting out the no-load bias. Over a low speed-range ratio (< 2:1), I would expect it to be fairly linear, but this is just a guess.

I don't see that tests into a battery compared to your constant voltage dump load will produce significant differences unless the controller is PWM and the duty-cycle hasn't been accounted for in the power out measurements. Pulse power measurements with analog instruments is less than precise unless intergrated.

Yes, isn't it amazing how a simple premise can quickly turn into a bag of worms.

[ghurd]

"I think your work may bring considerable benefit to people converting these small things, including ceiling fans and box fans."

That's me.

Having not been very successful at rewinding, I tend to glue magnets in anything that spins, and see what comes out of the pre existing wires.

The results tend to be higher voltage and lower amps. Worse in star.

Standard delta tends to (or seems to) have lower amps at low RPMs than Jerry Rigged.

Very rare to get high RPMs to compare delta and Jerry Rigged.

The resultas may be different with 24 or 48V, but overall I expect Jerry Rigged to win in my kind of use.  12V battery, factory windings with too many turns, not matched or great blades...

I started trying Jerry Rigged when he first posted results about an ECM.

G-

[Flux]

Don't worry about these results, I will re run the lot when I have strengthened the rotor, it was closer than I thought to disaster.

I will take a lot more readings and that will show the rogue ones quite quickly.

This in not a typical stator as far as losses are concerned at least not in its present vibrating form. It behaves much better in delta than they typically do.

I still have a feeling that there is surface loss induced in the magnets from the 3rd harmonic and the wide air gap is masking this. I can't do much about it right now but perhaps some day I will produce the delta equivalent for the proper star stator of this machine.

The calibrated drive motor is a standard way of measuring input power in industrial tests but no chance here, the motor losses are orders of magnitude greater than the input of this little thing.

You are right about the dump load, it is linear and in every way behaves as a battery but I will comply with Jerry's request and use a 24v battery and maintain its volts constant.

I think I will do the new tests as a separate diary, this is already quite long.

Flux

[elvin1949]

good morning Jerry

  I have been thinking abiut this a lot.

so i think the only way to know for sure is.

 Build not a 9 12 but a 27 36 genny.

A 3 in one thing.3 9-12 on one stator.

one star-one delta-one jerry-rigged.

all on one stator.

rectify all seperate-[3 genny's].

run them into the same battery bank.

sepetate meters for each one.

SAME LOAD_METERS WON'T LIE

myself i think you are right

later

elvin

[Jerry]

Hi Flux.

I've so far tested a small 3 coil dual rotor disc alt, a 14 pole GM altyernater with a doughnut NEO replacing the original rotor coil and a 3 coil ac motor conversion.

All of these with the same results.

A sloted type 3 phase motor conversion with 208-230v or 440-460 tpye rating could acomplish the same test I think. However this would be without the cheater coil that star needs. However I think it will show the same results that my other poun for pound tests have shown.

The most common DIY alt here is the dual rotor 9 coil 12 magnet arangement. This is the alt I'd like to see wound with 2 in hand and testes as I've tested my latest alt into a battery load load directly and the through any other type of electronic prossesing.

The battery only load test does change voltage as the test continuse but the diferance is so dramatic then even with this change the diferance is very aperarent.

I will ofer you this do the star test first. This will raise the battery voltage and reduce delta/jerry riged opertunity for a higher amperage showing. However even with that handicap ther delta/jerry riged will still show more power into the battery.

Sounds like giving star a head start is more then fair And while your at it through in a few more turns seperatly and add them to star only to help star.

                         JK TAS Jerry

[Flux]

Jerry

"The most common DIY alt here is the dual rotor 9 coil 12 magnet arangement. This is the alt I'd like to see wound with 2 in hand and testes as I've tested my latest alt into a battery load load directly and the through any other type of electronic prossesing."

I can do this test for you, I have a stator wound with coils that will allow this.

It is in no way fair to star , although you have the right weight of copper it has too few turns of wire that is too thick.

The present tests are being done with exactly the same weight of copper but of the right turns and section.

As soon as I get a chance I will run that test for you, it will at least be interesting to do it over a range of speed.

I don't know what you mean by any other type of electronic processing.

Flux

[scoraigwind]

I got here a bit late.  (I couldn't find the thread header sometimes.)  Quite a story :-)

I think the main thing to look at here is the efficiency.  if you want more power at lower speed, then you can always get that (under light loads)  by putting on more turns of thinner wire and trading efficiency for power.  

I never really noticed a difference in output between star and delta (and there does now seem to be some difference, if small).  I mainly notice the extra drag of the delta winding, robbing me of power around and just above cut-in speed.  Efficiency is what counts for me rather than raw power.  It's all a trade off in the end and higher power without equal efficiency doesn't actually gain you anything.

The other thing I like to look at is the shape of the curve.  I like a straight 'curve', or better still one that hooks upward at the end.  A hump in the middle does not work so well.  The reason is that the ideal power/speed curve for the blades is a cubic curve with a flat start and a big upward hook on the right hand side.  It helps to follow this curve as best we can.

Next thing I need to do is find out somehow exactly what is this jerry rigging that everyone is doing.  I like to see new tricks.  

[Jerry]

Hi Hugh.

Thanks for stoping by. There are several diaries pertaining to this topic. It goes back a mounth or so.

I had a thought so I did a few expiriments. After looking at both delta and star I was wondering why stars voltage is 1.73 times that of delta. The answer is very simple. We are taliking 3 phase here. So then its quite logical that all the phase are out of phase by 120 degrees.

My first concern was. If I have 2 coils producine 10 volts and I wire them in sires(star) I don't get 20v I get 17.30 volts. I concider that a losse.

So I concluded, If I make the delta voltage 20, this is what the 2 star coils would be if they were in phase, then I have gotting the 20 volt that I should have. At any given time only 2 star coils are working together but even at that point neither one is at full potential. That explains the 17.30 volts rather than 20.

The delta/jerry is basicly delta with the exception the 3 phase don't share a commom fullwave bridge. Each has it own. This in turn is equal to 3 sperate dc sources and the total of ther dc output is not degraded by pasing its curent though a neiboring out of phase coil.

The voltage is 20 not 17.3v and since all 3 dc are peralelled there amperage adds up.

The amperage in star is that of 2 out of phase coils wired sires.

I stated it this way. Three 20 volt 5 amp coils in perelell(the diodes provide the seperate but dc perelell conection) = 20v at 15 amps this is delta/jerry riged. Star on the other hand would be = to 2 10 volt 10 amp coils wired sires for 17.3 volts at 10 amps.

So I've put this to the test and gues what into a battery load thats the results I get. I've done this with a modifide GM car alt with a NEO stator, a small 3 coil 3 phase dual rotor disc alt and my latest is a 6 pole, 6 slot ac motor conversion with only 3 coils 120 degrees apart wound with 2 in hand 21 gage wire. This alows a normal star conection and a delta/jerry riged conection in the same alt. Open ac voltage for star 6.149v and open voltage for delta/jerry riged 6.729.

The loss in star voltage is right on track. Wattage test. 500 rpm wattage into a 6 volt golf cart battery, star 6.62 watts, delta/jerry riged 11.99 watts.

The results have been very simular in all 3 alts. It has been sugjested that to be fair to star and make up for its lose in voltage I need to wind a few more turns of wire. I did that in the small 3 coil dual rotor disc alt and star was still did less power into a battery load same rpm.

My plan is to wind a few more turns for star in my curent alt to give star the helping hand, it has been sugjested that star needs.

AS far as power requiered to operate a more powerfull alt. I'm aware of that.

After the helping coil for star is wound I may do a small wind tunnel test with a 49" blade and track mph and power out of the 2 phase types. This will be some time off however.

This is basicly a rehash of this subject that has been gone ever many times allready.

Here is the scimatic of the delta/jerry riged conection. I'm sure you've seen this befor.

Your thoughts are greatly apriciated.

                        JK TAS Jerry

[Jerry]

Whoops should have writen GM rotor not stator.

                        JK TAS Jerry

[scoraigwind]

Hi Jerry,

Thanks for bringing me up to date.  I now understand that the Jerry connection is to have 3 single phase bridges from 3 isolated phases - neither star nor delta connected. To get more volts you also double the number of turns compared to a star or delta connection.

I can believe that this would have a lower cut in rpm than star, because star will only produce 1.73 tmes as much voltage as delta, whereas yours will produce 2 times delta voltage at a given speed.  However we have to compare the efficiencies as well as the cut in speeds and I am pretty sure the efficiency of the Jerry winding as described is way down compared to star.

I don't really like single phase.  It seems a waste.  Using 3 single phase windings is at least a bit smoother but you are not benefiting from the ability to spread the output current over the full winding.  Your phases may produce higher voltage than star, but they will each have twice the resistance of star (thinner wire).  And I guess they will only be working one at a time (around cut in anyway).

In delta the whole winding is working for you at any given time, giving a resistance 2/3 of what you will get with 3 separate single phase circuits.  This is attractive except that you also get circulation of parasitic currents in delta.  There is another winding called 'open delta' but I suspect that is unbalanced.

Star gives 1.73 times higher voltage compared to delta, but has 3 times the resistance.  Current is 1/1.73 for the same power.  With the same power output, current squared is only 1/3 that in delta, so the copper loss due to load current in terms of IsquaredR is the same .  And there are no parasitic currents so this is my favourite.

It may seem like a loss to get only 1.73 times the voltage from two 'series' coils (star connection). But the beauty of it is that these coils are there, and can do this for you - i.e.it is possible.  You cannot place coils this size in the alternator and get them exactly in phase with each other because there is no room.  Yes you can double the turns on your coils but this is not the same as connecting two phases in 'series' (star) because there is not room for as much copper and so the resistance is much higher that way (twice as high).

I think I'll be staying with a star connection for now until someone can show me one that produces equal power with better efficiency.  Or more power with the same efficiency.  None of Flux's tests have shown that I can get this with delta or the Jerry connection.

As I pointed out earlier, you can get pretty much any power output you like by using more turns and ignoring the losses (up to a point where the alternator is 50% efficient) but the real trick is to get more power with less loss.

[Flux]

Jerry

Here are the results of the test you wanted comparing parallel star with series delta and series Jerry.

Purple delta in. Dark blue delta out. Light blue Jerry in. green Jerry out

Brown Star in. Red star out.

Flux

[kitno455]

i guess we are in the realm of exp. err. here, but it is interesting that jerry seems to make better use of the mags, and put more load on the prop at low rpms.

allan

[ghurd]

That is probably why my slower torque-ier blades work better Jerry Rigged in the low wind here.  Faster blades would be stalled.  ?

G-

[Jerry]

I'll start the planing stages of the temporary quike setup wind tunnel since wind test in my truck are weied as flawed.

I have a small hand held anamomiter. Not sure of its accuacy but it will be consistant.

Then I can check the power out of the 2 debated phase formates. I hope this will shed some light on the efficiencey debate.

I'll most likely use a 2.5 HP tredmill motor with a 24" industrial fan blade at a distance of ? ft away from the wind genny under test.

I will be able to control wind speed through a large varyable DC power supply.

Hows that for a test. I'm sure the flaws in this test will be pointed out but one thing for sure both phase types will be tested under the same exact wind condidtions.

                    JK TAS Jerry

[Reno]

If one wants to test two stator setups

Can't a dual stator unit be built

ROTOR-STATOR-ROTOR_ROTOR_STATOR_ROTOR

then all else will be kept the same since the test will be happening with all variables affecting both stators at the same time. Of course the rotors would be constructed the same. Anyone have 4 rotors laying around.

[electrondady1]

 four matching rotors? here you go.just waiting for the smoke to clear around jerry rigging

[ghurd]

Wow!

[Flux]

I have decided to throw in another connection that was possible with this machine, that is 6 phase.

Rpm   then watts out, watts in and efficiency

1.  350    69.6    110.7   62.8%
   
2.  375    200.39  275     72.8%
   
3.  400    343.6   476.7   72%
   
4.  450    410.4   618,8    66.3%
   
   

I can't see how to plot these with the others without causing total confusion so once again someone may want to plot them separately.

Flux

[Flux]

Sorry those speeds are mixed up.

Should have plotted the figures as a check.

Corrected figures

1.   350  69.6   110.7   62.8%
   
2.   375  113.6  178.7   63.5%
   
3.   400  200.3  282.3   70.8%
   
4.   450  331.1  503.5   66%
   
5.    475  411.3  666.3   61.7%
   
   

Perhaps I should point out that all these tests have been into a 12v battery and I have tried to keep from 13.5 to 14v

Flux

[nothing to lose]

"a 14 pole GM altyernater with a doughnut NEO replacing the original rotor coil"

Jerry,

Was that with stock windings for the GM alternator and the finger plates? Or did you rewind it? How did it workout power wise?

I have 3 donuts I got specifically for such a project. I think mine are 3"OD x 1.5" ID and 2 are 3/4" thick (each), the other 1/2" thick.

I just got a 12ton press about 10 days ago, missing a spring, just got the spring so I can use it now.

I was actually searching for updates on the 6 pole test genny with those arcs to see if done and how it's working when I saw you mentioned the GM alternator.