Permanent magnet alternator hydro system problems

[danifarre]

Hi all

I´m trying to made a homemade pico hydro system whit a banki-like turbine (25 cm diameter) and a permanentmagnet alternator (17 cm diameter, in which the magnets are fixed in the centr, and the coils move around it). Is like the FE1012U (404 PMG,www.futurenergy.co.uk, 12 volts)using diode bridge rectifier to convert AC to DC. .

When i run my turbine  without cnnecting it to the regulator (a Xantrex C40 used in PV charge controller mode, NOT in diversion load mode), it runs at an optimal speed (around 400 rpm), but when i connect the PMA to the regulator, speed drops and the power produced is really low.

>Is this normal? Why?

Could a turbine with a higher diameter move easily the PMA? in this case, what will be the minimum requiered diameter in my turbine?

sorry for the inconvenience, but i´m new in this field, and i need help

best regards

[Flux]

You don't give a lot to work on, but the most likely conclusion is that you are extracting all the available energy from the turbine.

Typically the loaded speed will be about 1/2 no load speed so if you are running near 200rpm on load then you are about right. If the speed is way below 200 rpm then your alternator is too powerful for the turbine or its cut in speed is wrong.

Forget the charge controller for now and connect the rectified output of the alternator to the battery and check the current. If speed is well below 200rpm then try raising the battery voltage temporaliarily to improve the matching ( 12v intended system, try 24v battery) if you get more POWER ( not amps) then your matching is wrong.

Need details of head and flow to help any more than this.

Flux

[Nando]

What is your name, I get very nervous when I am talking to Ghosts.

You stated the problem but you do not state the conditions to define the reasons for the problem, and unhappily nobody in this group have the capabilities of reading minds at distance or even at very close distances.

You need to supply the head and the water volume to define the proper parameters of the banki to see if the banki you built can draw the peak power available in your site.

Also supply the information of your piping ( diameter and length) as well as how you are supplying the water to the banki ( be exact and in detail because the Banki Nozzle is very -- capricious ).

The curves for your alternator are for wind mill available power and what you need is the generator power versus RPM and Voltage versus RPM open circuit.

Also, the need to know the internal resistance of the phase windings and the Volts/RPM of it.

I see that at around 230 RPM the available current is about 1.8 amps.

If you have measured, AT NO LOAD, the RPM of the banki, at around 400 RPM, then you MAY have a wrong Banki diameter.

Supply the sites parameters, as above requested, and I will tell what can be done to solve your dilemma.

You can as well connect directly with me, correct the anti-spam of the email address.

Nando

[scottsAI]

Danifarre,

Unloaded banki will turn at the speed of the water coming out of the nozzles.

Properly loaded the RPMs will drop in half.

With the controller and no load... not sure what all your doing.

Like everybody else said, details...

How many watts were you expecting?

Have fun,

Scott.

[danifarre]

OK...., my name is Dani...

other details about my turbine are

Flow=15 l/sg

head=10 meters

Today i have prove another thing...i have changed my noozle (now is a 2.5 cm x 11 cm) and some more power has been obtained (around 5 amp 12 volts sistem).

Nevertheless, when i run my turbine without connecting to the battery, current rise to 130-140 volts!!!!?

i really don`t know what happens

thanks

[Nando]

JON:

Now that we have parameters I can see you problem well.

You are producing the voltage expected at the RPM the generator is rotating.

You forgot to include the pipe size and pipe length to give you a bit more accurate power calculations.

The power available

15. l/s
    
10. meter head
    
    

Gross Power watts = 12 * 10 * 9.81 = 1177 watts

RPM for peak power

Maybe around 700 to 900 watts available depending on the efficiency of the overall system ( includes pipe losses, Banki and generator efficiencies)

Water velocity = Square root ( 2 * 10 * 9.81) = 14 m/s

RPS = Rev Per Second

Banki Peak RPS = 14 / 2 = 7 m / s = 700 cm/ s

Generator RPM with a banki 25 cms

RPM = (RPS / PI * diameter ) * 60 = (700/ 3.14 * 25)* 60 = 535 RPM

You can not slow the Banki down like in a wind mill because the power will go to nil, and a way to use the present banki would be to have a voltage conversion to the 12 volts you aim to have as a bank.

You have a BAD marriage, let's try it does not go into a divorce and getting a new replacement.

What solution you may be able to use.

You can not use a MX60 since the voltage generated will be much higher than its capabilities.

You could get a PWM switching power supply WITH PFC input and wide range ( 85 to 240 AC) and the 12 volts output adjustable to the 15 volts for the C60 to operate properly.( may be a bit costly and, as well, you will need a good ELC = Electronic Level Controller to keep the Gen RPM to a safe value).

Change the generator to a 6 poles motor and convert it to a generator with capacitors and get transformers to convert to 15 volts nominal for the C60 operation, you could use the available AC power (800 or so watts ) directly and a smaller charger for the battery bank.

You will need an ELC.

You could start cold again and design the system to produce the watts that the water source is capable in a way that is practical for you and your use.

Lastly you could use a pulley RPM conversion to attain the low RPM needed for the generator to produce the peak power available in the Banki.

YOU WILL NEED to define the Voltage Versus RPM of the generator ( the info in the site is for wind mills and the loading effects of the load on the wind mill blades, which is represented as a curve for the generator) WHICH in reality is the impedance curve of the wind mill blades.

Let me know

Nando

[Flux]

It is perfectly obvious that you have a high voltage alternator that would possibly match a 80v system but may still be on the high side.

You are dragging that alternator down to effectively a short circuit and most of your available power is heating the alternator windings. The simplest but fairly costly solution would be to use a 3 phase transformer between the alternator and rectifier to reduce the ac open circuit voltage to about 20v. You will need to watch the frequency rating of any transformers and you need to supply the turbine speed and alternator number of poles.

I can't understand your flow figures but assuming it is meant to be 15L/s then you should have about 1kW available, of which you should be able to extract at least 500W fairly easily if you can match the alternator.

The better solution may be a MX60 charge controller but you would need care with open circuit voltage and the cost would be higher than transformers.

Flux

[hydrosun]

I agree that the Mx-60 could be used on this system. Solar panels with over 80 volts open circuit would clamp the voltage to protect the MX60. Whether this would be the best way to go is up to you.   If you have to run wire a long distance this would allow low losses at the higher voltage.

Chris

[Nando]

Adding to Flux statements.

The idea of the transformer may be a solution BUT You need to get the voltage/RPM curve without load, then what is the phase winding resistance

Also the number of poles to see if the operating frequency at 1177 RPM is around 400 Hz to be able to use many available transformers in the surplus market.

I have the feeling that it may be a 6 poles generator for 60 Hz at 1200 RPM.

Inform and between many of us a solution may be found for your successful hydro problem solving.

Is the 140 volts, DC or AC, single phase measured or 3 phase, inform to see it you can do the salvage with transformers.

Is the generator in STAR configuration and can it be modified to DELTA configuration ?.

For the time being, forget the idea of a different diameter Banki.

Nando

[danifarre]

Hi again...

i forgot to include the pipe lenght and size

the pipe is a PVC pipe with 90 mm of diameter and aprox. 22 meters long.

If i have understand, my problem is that the PMA runs too fast, and produce too

current for a 12 volts system? And why the alternator blocks itself? Is caused by overcurrent?

Other observations about the instalation:

- AC Current is transported along 150 meters in a 3 phasic way...

-Then goes to the rectifier bridge and rectified DC current goes to the charge controller (Xantrex C40).

At the end of these proves, diodes were really hot, as was also the permanent magnet alternator... Is possible that diodes had fused? and what about the PMA?

Thanks

[Flux]

"If i have understand, my problem is that the PMA runs too fast, and produce too

current for a 12 volts system? "

No not really, the truth is that it is a high voltage alternator and has lots of resistance. You could run it much slower and match the 12v but you still will have far too much resistance to be efficient. You either need a more suitable alternator or some method of transforming your high voltage to a lower one. Your cable run is rather long so you might as well stick with the high voltage alternator and transform the volts in some way.

Yes I would expect the alternator to be hot, that is a good sign that you may be managing reasonable power from your turbine ( but wasting it in the alternator). I would not expect the rectifiers to be hot, they are probably much too lightly rated and not heat sinked properly. If they will not carry 5A without heating then they have no chance if you get the current up to the 50A that you might be able to get. I doubt that they are faulty or connected wrongly but it is a possibility. Probably a short term overload of the alternator will do no harm. I doubt that it will produce the figures the makers claim under hydro conditions if they intended it for wind with forced air cooling and a very intermittent duty cycle. Being a pessimist I doubt it will make 1/4 of its nominal rating within its designed temperature rating.

Are you stuck with 12v it is a real pain with long cable runs, is it possible to try it temporarily at 48v even if it means stringing up a few car batteries, I think you would find it a far better match.

Flux

[Nando]

Dani:

Where are you located, UK or USA or where ?.

Your problem is two fold,

1. The Banki RPM is too high.
   
2. The generator was designed for a much lower RPM.
   
   

Also, you do not know what the Voltage versus RPM is (open circuit) that will tell you what to do to solve the problem in a proper way.

There is a alternate solution and it is the use of a MX60 and the addition of an ELC ( Electronic Level Controller) to regulate the voltage to 100 volts maximum.

I went to the site you suggested and did a rough calculation of the Volts/RPM and guessed about 70 to 77 millivolts / RPM and with the 1177 RPM that the turbine rotates, the generated voltage runs from 84 to 92 or so volts ( this are rectified volts ).

Another possible solution is to convert the STAR connection to DELTA connection if possible to reduce the voltage by 1.73.

Nando

[danifarre]

Hi again...

I´m from spain, and i want to install the turbine in a region between galizia and leon..

Ok, and what about pulley reduction?

Actually i´m using a pulley sistem: a 28 cm diameter pulley at the turbine, and a 8 cm diameter pulley in the generator...

Maybe direct drive? what about if i change the pulleys (i.e, the 28 cm to the generator and the 8 cm to the turbine)?

One specification....current distribution is made in AC triphasic mode...

thanks again

[danifarre]

All you said that using a MX60 charge controller could allow to use this system....

And what about my Xantrex C40? It can hold 120 volts DC with open circuit, and 40 Amps (peak 85A)....

[Flux]

I have had a look at the figures for your alternator and it seems to cut in at 12v at about 220 rpm. If you are seeing 130v ( I cant remember if ac or dc) open circuit then you have it running near 2000 rpm which is far to fast to match the turbine with a 12v load.

Direct drive would probably be much nearer and that would bring a great improvement.

Now the snags. That alternator is designed for wind power so at about 20A out its efficiency is going to be down around 50% Add to this your long line loss and your overall efficiency is going to be much lower than this, so you have a problem even if you get the turbine matched to a sensible speed ( 330 rpm from the alternator figures should give 20A)

You still don't say if you are stuck with 12v. That alternator would run fairly efficiently at about 1200 rpm charging a 48v battery. If you must use 12v then you will need to keep the speed up into that region or higher and use a transformer or other voltage converter if you want decent overall efficiency.

Yes it is a low speed alternator for wind, but if you want it efficient and capable of the output you want, then you have to treat it as a much faster higher voltage device and take steps to match it to what you want.

These factors are far from obvious and I can easily see why you made the choice on the limited information available. It can do what you want at decent efficiency if you get the speed right and match the load but you loose most of the simplicity of the original concept.

Flux

[Flux]

The MX60 is a mppt buck converter that will convert high voltage low current to low voltage high current.

C40 will not help in the least with the voltage conversion, it will prevent the battery from overcharging but at present that will not happen unlesss you can increase the output.

Up until the time that battery becomes fully charged the C40 will do nothing.

Flux

[danifarre]

I would like to maintain the 12 volts instalation.......

What about changing tthe turbine? Previous to that banki turbine, i have made a home made water wheel, 1,20 meter diameter, with superior water charge...Could this waterwheel works more efficiently tthan the banki turbine?

[Flux]

Within their limitations a water wheel can have the same level of efficiency as a turbine but that is not a possibility in this case with a high head you would need an overshot waterwheel the diameter of the available head. Other forms of waterwheel such as the Poncelet would be a modification of a turbine in this case and would suffer badly in comparison.

The trouble is almost certainly not your turbine, there are enough mechanical and even more electrical reasons for the poor results. If you must stick to 12v then you need feed cables about 1" thick or you must use some form of voltage conversion. Even with the thick cables that alternator will have poor efficiency at 12v at any reasonable power out. You could use thick cables and build a special high efficiency 12v alternator but the cost will always be high. 12v on long cable runs is a nightmare for anything other than wind, where the cable drop may help stall troubles.

Flux

[danifarre]

But, if i distribute current from the turbine as 3 phase AC, losses don`t will be LOWER? Then, conversion to DC current is is made beside the controller and the battery bank...

Regarding waterwheel, it can be placed with the head i want...the only thing that don´t change is the lenght of the distribution wire.....

Anyway....in your opinion, what of the options i have will be the cheapest one? maybe usin a transformator? What to transform: 3-phase AC or 2 phase DC? which transformator size will be the most apropiate?. MAybe a 24 volts system, or 48 volts system with posterior transformation to 12 volts resolve the problem without turbine modification?

And lastly, could the waterwheel (1.2 meter diameter), considering that it can be placed at the desired head, give an optimal efficiency with a rpm multiplication by pulleys, near to 10 fold?

I really don't know which direction follow....i´ll be happy if, whitout many modifications in my actual system (that includes a possible direct drive application, or transformator use) at least 10 amps at 12 volts could be obtained.

thanks

Dani

[Flux]

"But, if i distribute current from the turbine as 3 phase AC, losses don`t will be LOWER? "

No in most cases this is wrong ( depends on the alternator reactance) and in any case the effect will be small.

I think the waterwheel approach is a dead end.

I am not sure what to advise you, the simplest most effective and almost certainly the most expensive way would be to gear the alternator to the Banki with a ratio that gave you about 120v dc after the rectifier on no load, that would be safe for a MX60 and it would set the turbine operating speed to optimum.

Transformers will work but selection is not easy and if you get things wrong you may end up worse off. You need a 3 phase transformer or 3 single phase units. Don't play with 2 phase.

I can only give you general advice, maybe you should contact Nando direct, he may be able to give you more detailed advice.

I am sure your cheapest solution would be to abandon the 12v. Work with 48v and change your belt drive to match the alternator at 48v. The line loss will be small enough not to worry about. The alternator efficiency will be reasonable ( possibly 70%).

If you have to use 12v then there is no easy cheap and efficient solution but if you change the belt ratio to something much nearer to what is needed ( alternator no load speed about 600 rpm)and see what you get with the alternator and line losses then you may get far more than you have now. If the power is free and comes 24 hrs a day it may be enough.

Those are your options you have to make the choice depending on your financial means and probably more so on your ability.

Flux

[Nando]

Dani:

You are in a quagmire and do not know what to do, I just sent you a message to your @hotmail address, in Spanish, for you to decide to connect in a different way to solve your problem, that I see you need a lot of changes to save the project.

You need to relax and do an analysis of what you have, what you need and how to solve the problems that need change, or even re-do to attain the proper and efficient hydro system.

It seems that 600 to 800 watts can be harvested if properly done and the solutions are not by doing a bit here and a bit there but by analyzing what you have, what is wrong, what can be used and what needs to be changed to get your harvested peak power.

Also, a detailed analysis of what you have without the sudden addition of one more fact, like the pulley set up 28 to 8, making the problem worse.

It is your decision.

Nando

[Nando]

Report to all:

I have been connecting with Dani to determine the solution of his problem and after getting more or less the description of the overall system, I see that he needs to re-built his hydro to attain the harvesting of the available power in his site, and one of the changes is the generator that is not adaptable for his site, another change is the Banki and its nozzle that did not help in the process, by having a too large nozzle size for the pipe diameter and the water volume limitations.

Nando