Testing my alternator

[tlucier]

We built a single phase 12 volt alternator using 12 inch rotors and 24 magnets all bought from Forcefield.  everything is put together, water coming down the hill at 40 psi in two inch pipe.  Hooked up to a trace C-40 and a Xantrex DR2412 inverter.  We're using two Deka 200 amp hour batteries. The charge controller/diverter reads voltage between 12.2 and 14.4 volts, amps and watts seem negligable.  I used a Fluke 1000, amp tester at the alternator after the rectifiers set on auto AC/DC mode and get no reading.  switching the tester to AC mode I get a reading of .5,  what does this mean??  It should all be DC. How do I best test for the output?  Is it possible that the rectifiers are bad and I am getting AC in the line??  I'm a newby so please be patient with me. All help is appreciated.

[Flux]

Probably true.

No details to go on, not interested in your C40 , inverter or type of battery.

It would be more useful to know something about the alternator and turbine. Basic question, what speed does the turbine run at? What ac volts does the alternator produce at this speed? The implications are that the alternator is producing less than 10v ac when driven by the turbine.

Why on earth choose single phase but that is not the issue at the moment.

Unless you can measure the turbine speed and the open circuit ac volts from the alternator there is little help anyone can offer. Details of alternator winding and perhaps a picture of the turbine would help a great deal, failing that a description of the turbine.

Flux

[tlucier]

Not having much electrical theory prior to my daughter and I building this thing for a school project we used Hugh Piggotts 2005 edition of "How to build a wind Turbine" and most plans were in single phase.  I still don't understand the concept of 3 phase or how to convert to DC or the pros and cons.  Any suggestion theads here to look up or other litature would be greatly apprecieated.  In retrospect a 24 volt system would have also been better.  I believe that this winter I can build a new stator to accomodate the change without changing the rotors or housing of this unit.

As to description it is built on a trailer hub with two rotors each with 12 magnets that are 1x2x1/2 inches, it has 10 coils of #15 wire wound 80 times with a 1x2x1/2 hollow core.  Wire go to 5 rectifiers (also purchased thru otherpower)

I have a simple handheld tach on order because I have no Idea of the speed. the book was not very specific on how to test the output.  maybe somebody could help me with this.  What is optimum.  I hope to control the speed with the water supply, or is faster better?

I will try to send pictures of this tommorow,  thank you again for your help.

[kurt]

all the alternators in Hugh Piggotts 2005 edition of "How to build a wind Turbine" are either 3 phase or 5 phase if you got single phase you done something very bad.

[electrondady1]

hello tlucier,

for single phase you would need 12 coils and just one rectifier.

3 phase is a bit tough to get your head around at first ,

but once you do it will seem simple.

[tanner0441]

Hi

Single phase for optimum would use 4 diodes in a bridge formation, and if it is giving any AC out the frequency would be related to speed, so the speed could be measured with a simple frequency counter as found on decent multi meters.

Also are the windings all in the right directions.

Brian

[Flux]

Seems as though you have built the 10 coil version which is parallel 5 phase. This should be perfectly ok but I have no idea why you thought an alternator intended for a wind turbine could be used for hydro without considering speed or other matters related to power matching.

You can quite easily hand crank the alternator alone ( may not be possible on your turbine) and measure the dc volts after the rectifier. It will probably reach 12v at 200 rpm or a bit less. With a bit if practice you should be able to crank at that speed but it may be easier to crank at 120 rpm ( 2 turns/sec)  and measure the volts.

If the volts are reasonably close to this then the alternator is ok and you are looking at turbine speed or power problems.

It should turn easily with no significant drag. If you short the dc output leads it should be stiff to turn but smooth.

If you have significant resistance to turning with the dc leads open or if it turns "lumpy" when shorted then suspect connection or rectifier trouble.

Flux

[tlucier]

Thanks for getting back on this... It's obvious that I don't know much about this but I can feel the lights coming on.  I went with the wind turbine design for the low RPM, commercial units need more head, and this was more fun to build.

When I short the dc there is significant drag.  will this hurt the rectifiers with continued use??  Also how do I test the rectifiers to make sure they are all working correctly?  please humor me but what do you mean by "Lumpy"??

[Flux]

If you have used the recommended rectifiers they will be more than able to stand the power you can expect the alternator to produce. The drag is inherent in the way that mechanical power is converted to electrical power ( no drag, no work done, no output).

You will not be able to get the same peak power rating from this alternator as a water turbine as you could for wind. The wind has a low duty cycle whereas hydro is 100% You will need to limit your power to something the stator can stand without cooking.

Single phase alternators don't turn smoothly on load, the torque pulses as the magnets pass the coils. Three or 5 phase will be smooth to turn under load, if you feel significant variations in torque " lumpy" then you have something wrong.

Flux

[tlucier]

This is a five phase alternator but you bring up a new concern...you mentioned cooking the stator... will these not handle continous use at 190 to 200 rpm?  I had assumed that wind turbines will work at slower speeds but not as efficiently, is this something that I can control with water pressure and rpm's.  Now I am using two 1/2 inch nozzles to run the pelton, I can reduce or increase the size of these to better tune the speed.  I can also eliminate one but worry about balance.

[tlucier]

This is a five phase alternator but you bring up a new concern...you mentioned cooking the stator... will these not handle continous use at 190 to 200 rpm?  I had assumed that wind turbines will work at slower speeds but not as efficiently, is this something that I can control with water pressure and rpm's.  Now I am using two 1/2 inch nozzles to run the pelton, I can reduce or increase the size of these to better tune the speed.  I can also eliminate one but worry about balance.

[vawtman]

 Would be cool to see a pic or video of it.Is that possible?

 Mark

[Ungrounded Lightning Rod]

I used a Fluke 1000, amp tester at the alternator after the rectifiers set on auto AC/DC mode and get no reading.  switching the tester to AC mode I get a reading of .5,  what does this mean??  It should all be DC.

In AC mode looking at rectifier output you'll see the ripple in the current as the various phases peak, fall back, and are replaced by the next phase.

Your battery will clamp the voltage in the 12 to 15 volt range.  If you're seeing variations in that range you're probably charging.  So I'd suspect the meter.

Try hooking in an in-line ammeter, in case your fluke 1000's hall sensor isn't sensitive enough to do DC properly in clamp-on mode.

[Ungrounded Lightning Rod]

Also:

24 magnets on a dual rotor is 12 pole.

How many coils do you have to get your 5 phase and how are they hooked together?

[tlucier]

ten coils, five rectifiers.

[tlucier]

I'm sure i'm  charging, how much I don't know.  The lites come on but the microwave works intermitently.

still want to know how to test 4 diode rectifiers....thanks for the help

[Ungrounded Lightning Rod]

Use an ohmmeter (with a diode test setting if available) on the bridge with it out of circuit:

 - from each AC terminal to each DC terminal

 - with both probe arrangements.

This is a total of eight measurements.

You should get:

 - Essentially open circuit with one arrangement of the probes.

 - Strong conduction with the other arrangement.

 - The arrangements are swapped when probing a + versus a - terminal.

 - Except for this plus/minus flip, all four pairs of measurements should be very much the same.

If all four diodes are OK each set of measurements will be essentially the characteristics of the individual diode between the two pins you're probing.  If one diode is shorted you'll get confusion on the other diodes' measurements - but you'll also find the shorted diode.  So it's easy to do a go/nogo test but it's a bit tougher to diagnose a fault.  (Fortunately you don't NEED to diagnose a fault, since you're going to discard any failed bridge, not repair it or try to kludge something out of its still-OK portions.)

Two things:

 - Because the meter is expecting a resistor and it sees the diode voltage drop it will look like the diode is quite resistive.  Don't sweat it.  It's a metering artifact.

 - When acting as an ohmmeter a multitester usually puts the + probe voltage on the - probe and vice-versa.  So the conduction happens on the opposite probe arrangement from what you might expect.

[Flux]

I suspect that your alternator is working ok, I am not sure why you are so worried about the rectifiers. If it hand cranks freely on open circuit and becomes stiff to turn with the dc leads shorted then it is most likely ok. If you have used new bridges and connected them correctly then I doubt that you have a rectifier problem. I was mentioning the " lumpy " turning more to question connection errors than a rectifier fault.

As wound that alternator will just about cut in at 200 rpm, it will give no significant power at that speed, you will need to get up to 300 rpm to get much out of it and if you have 40 psi at sufficient volume to feed 2 half inch nozzles you should be able to get a fair bit.

If your is turbine only doing 200 rpm then you will not see the tiny current on a 1000A Fluke meter. You could try looping the cable through the clamp 10 times and make it 100A FSD.

You have got a lot of confused ideas, the issue is not that the alternator will fry at 200 rpm, in fact it will produce so little that it won't really be on load.

The 200 rpm is cut in speed for the wind turbine, the operating speed at rated power will be nearer 400rpm and for hydro you will need to spin it at over 300 rpm to do much good. Wind works at variable speed, hydro is essentially fixed speed and you must wind your alternator so that the load on your turbine brings your turbine no load speed down to about 1/2 and this must be with the alternator producing an output power that matches the input power to the turbine.

Just disconnect the dc connection from the rectifier to the battery and the turbine will run up to its no load speed. This should be about double the speed when connected to the battery. If there is no speed increase when you open circuit it then the turbine is running on no load.

The issue about stator heating is nothing to do with low speed, the simple truth is that it will not stand a high continuous power out without over heating, you don't have a strong wind blowing on it to cool it and hydro power is constant without peaks and low periods for the stator to cool.

The design within its limitations is excellent for hydro but the power you can expect out is related to its operating speed. The slower you make the winding then the less power it will give without heating.

In fact the more I think about all this lot the more I wonder if you have gone the other way!. 40 psi on a small diameter Pelton may be aiming for a far higher operating speed than your alternator will match, in which case if you open circuit it and the speed shoots up to a very high speed ( in the 800rpm plus region) then it may be that you have dragged your turbine right down off its power curve and you have the opposite effect to the low speed issue.

Unless you give some details of the turbine then all this is total guesswork, I am now wondering if the turbine wasn't intended for a modified car alternator and intended to run in the 1000rpm region and you are loading it right down to about 250 rpm,

Flux

[Flux]

Thanks for that.

It's bed time but I will have a better look at this tomorrow.

My immediate reaction is that the buckets are not Pelton but would most likely work as a Turgo. If you hit those with a central jet as in a Pelton the water discharging will not clear the wheel and you will have dreadful losses from turbulence.

With the runner so close to the top I think you would even be in serious trouble with a true Pelton bucket.

It looks to me as though you need to cut holes in the metal plare between the turbine and alternator so you can angle the jets down at the buckets at about 45 deg and treat it as a Turgo runner, the discharge should then run clear at the bottom of the runner.

The diameter of the runner looks to be large and you may be short of speed, this combined with turbulence if you are aiming on the centre line may be holding the turbine back. I suspect you are generating a small amount of power but not much.

Is the 40 psi dynamic pressure with the nozzles discharging or static pressure with no discharge?

Flux

[kurt]

tlucier, I had to remove your comment with the photo that photo was HUGE. we have image posting rules here. images have to be sized to no larger than 640 x 480 pixels and less than 150 KB file size or they are subject to removal. please resize and repost your photo. thank you.

[vawtman]

Hi Kurt

 What i did to resize it was to right click on the pic and email it back to me.Windoz resized it for me.

 Tried to help him with a resized pic.Could'nt figure how to bring it up here though.

 Sooner or later i wont need my daughter to help me with pics anymore.Hopefully later

[tlucier]

Sorry here it is in smaller size

[Flux]

Assuming that your head is 40psi with the nozzles discharging then that is a head of about 90ft. The jet velocity will be something less than the theoretical root( 2gh)

That gives root (2 x 32 x90)  or about 75ft/sec. The runner bucket velocity will be about half this for a Pelton or a bit higher for a turgo but near enough so perhaps 38ft sec.

I can't even guess your bucket pitch circle diameter but if built on a wheel then perhaps 18" so the circumference may 4.5ft. This would give us 8.4 revs/sec or 500 rpm.

Your alternator should be making lots of power at that speed and in fact it may be rather slower than ideal.

There are far too many unknowns in this to be of much help to you, the most serious being the way your jets are aimed at those buckets. I am inclined to think that you are not extracting much power from that runner if you are aiming the jets as intended for a pelton. You need to compare no load speed and speed when connected to the battery as a first step to see if the turbine is in with a chance of matching the alternator.

Flux

[tlucier]

Sorry it took so long to respond.  My hydro unit is in place at a remote hunting camp and I only am able to go to it every now and then.  Several hours of bad dirt road.

I took up a hand held tachometer this last time to try and get some better info.  What you had assumed is pretty much correct.  diameter of the pelton is approx. 18".  They are metal bowls (Walmart camping section) bolted to arms welded on a trailer wheel.

We tried changing the two nozzles this last week to see what would be optimum.  The 1/2 inch nozzels produced around 450 rpm in no load and 205 when connected to the battery/inverter.  This uses a lot of water and the pressure drops down to about 30 psi.  We tried changing the nozzels to 1/4 inch and and numbers fell but presure went up to 40 psi.  Finally we opened the nozzels to approx. 3/8 and the rpm went to 570 no load to 210 under load and maintained 40 psi.  Not much overall difference but we needed to try to reduce the amount of water used to maintain a supply of drinking water.

I am not familiar with with what is expected from this design for windmills but I would have thought the load would not drag down so much rpm.  ...or do I have some other problem?

Again, thanks for all the help its been a fun learning process.  The best part is having lites on at caamp and not listening to a generator all night.