Looking for Amps

[Shadow]

I've got a dual rotor, 10 foot blades, 9 coils, 12 Neo's, 140 turns #17 wire, it hits 48 volts about 152 rpm. I have a string of 8 -6volt telephone batteries. They are pretty much charged up they show 49 volts or over. So today I hooked up a 1500 watt, 120 volt heating element into a pail of water. Wind is very strong, mill is furling half the time. But no matter where I check the amps, I get readings of 3 or 5 or 8 was the highest. I used 2 diff gauges and the meter, all read the same. Checked between wire being fed into the batteries by the mill, 3-5 ammps, checked at the element, 8 amps after about an hour. Where are these 35-40 amps I hear everyone talking about from their Windmills? If I unhook the element,and just let the batteries charge, they go up to 50 plus volts within about 1/2 hour with no load. So the mill is charging but how many amps?.. Thanks for any comments

[Shadow]

Not sure if its relevant, but when I check any two of the three phases, I get 38.6 volts AC.When connected to batteries.

[Norm]

  Do you have an ammeter?...it'll tell you how

many amps are going where, using a multimeter

and a shunt(the built-in ammeter usually doesn't

have that high of a range, so you measure

voltage drop in a certain length of wire of

 a certain guage instead,go to TomW's site which

has an excellent article all about shunts and

how to make and use your own.

                  ( :>) Norm.

[MelTx]

 Some guys can take 1 inch of rusty steel wire & a piece of old loadstone and get 8 megawatts.I spend $68,000 and get 14vdc and 2 amps.I hope you find where your amps went cause I am going to look for mine over there.

[Flux]

you are not going to get 35 - 40A at 48v, but you should get 12 to 15 .

You really need to be able to measure the prop speed but you need a frequency meter for that. It may be furling very early, do you have any idea of the wind speed?

It is possible that it is stalled but I have no idea of your prop details.

The voltage you quoted on the ac side seems right. What cable do you have between the mill and battery but it is unlikely to be a problem at 48v.

Flux

[Ungrounded Lightning Rod]

I've got a dual rotor, 10 foot blades, 9 coils, 12 Neo's, 140 turns #17 wire, it hits 48 volts about 152 rpm. I have a string of 8 -6volt telephone batteries. They are pretty much charged up they show 49 volts or over. So today I hooked up a 1500 watt, 120 volt heating element into a pail of water.  [...] checked at the element, 8 amps after about an hour.

A 1500 watt heating element, glowing a nice red, will pull 12.5 amps from 120v.  That makes it 9.6 ohms.

If you put 9.6 ohms across 50 volts you'd get about 5.2 amps.  But even if your element were in free air it would be cooler and have a somewhat lower resistance - and you dunked it in water.  So 8 amps (6.25 ohms) is reasonable on the discharge side.

The charge side is another matter.  Output voltage is held steady by the batteries, which also holds the prop speed close to steady and extra wind force goes into more current.

But your mill is furling - so it's taking it upon itself to limit the wind power through the turbine by reducing the cross-section exposed to the wind.  The most likely problem is that the mill is furling too soon.  You can add some weight to the tail to make it furl later.

Another possibility is that you've got too much resistance in the circuit - wire in the genny too thin, wire from the genny to the battery too thin (or too long for its thickness).  If that's the case the prop will change speed a lot as the wind va  (Any speedup in the turbine once it's up to cutin represents energy lost to wiring resistance.  There will be some.  But if the prop speed doubles after cutin then half your power is going to heat wires rather than charge batteries.)  Before you tweak the furling too far you should check for this (by measuring the resistance with the prop stopped or inferring it by measuring prop speed - or alternator frequency - versus charging current.)  With too much resistance the mill may overspeed even with the load attached if you furl too late.

[Shadow]

Ok, I have a little more info, Wire size from generator is 12 guage extension cord type(very heavy, may even be 10 cant find a number), 60 feet long. Wind is fairly gusty at the moment  about 20-30 mph, checked prop speed with digital tach (using reflective tape on back of back rotor) was hitting 44 volts at 132 rpm open circuit, (I need to be 10 inches away to get a reading, gets scary real quick when it starts to swing around in the wind and I'm on a step ladder, cause after that rpm it takes off like a rocket!, before I can run 60 feet to hook it up to the battery) It slows back down and levels off at 160 rpm showing 50.9 volts at the batteries. It is not furling at this speed but lots of yawing slowly back and forth, with tail rising up and down but staying consistant at around 160 rpm . Hope this info helps.

[Norm]

  Why don't you install a magnetic reed switch

with a magnet on the hub...connect it to a white

led at the base and you and your digital tach

can take a safer reading from there?

            ( :>) Norm.

[kww]

Sounds like you might not be aware that trying to power a 120 volt element with around 48 volts isn't going to "drive" it very hard.  Even at 60 volts the element would use far less than half the amps used at 120 volts.  There are two things I know of that you can do, increase the voltage or reduce the resistance of the element.  If you were using an electric heater type element you can just shorten the length of element between the hot and neutral.  To increase the voltage of your alternator a 3 stage voltage multiplier(one for each phase) made of only capacitors and diodes might do the trick.  I'm working on this very thing.  My turbine/alternator sounds very much like yours.  I've been running 250 watt heat lamps.  With 3 stage multiplier circuits I was seeing 125 volts powering 3 250 watt heat lamps in gusts the other day.  With a single stage multiplier(doubler) I got around 85 volts max., but after about an hour of very high winds smoke started pouring out the box as the caps couldn't handle the load.  The more stages the less current can flow, at least at lower voltage, which keeps the caps much cooler.  Although low wind output went down with the 3rd stage added(I tried one and two stages, and more) higher wind speed output actually increased because the voltage could go higher, I guess.

Here's 3 250 watt lamps and a 200 watt bulb running at 76 volts DC continuous on the single stage multiplers.  You should have seen them going at 125 volts with the 3 stage multipliers. :-)  Didn't get a picture of that.  Btw, the turbine is over 300 feet away and connected by cheap 14 ga. romex.  

Kevin

[Shadow]

 Cool, Yes I realized that 48 volts wasnt gonna drive the 120 volt element too much but I guess I was expecting more amps to be present at some of these loads and tests I've been doing. I guess it may not be a problem butI keep thinking you need lots of amps to charge a string of batteries in decent time.And was wondering if I need to make some changes to keep up with the demand.

[Flux]

Good, it was the speed on load that I wanted not the speed off load.

Is that a real wind speed measurement or a guess?. If you are really going up to 30 mph it may indicate stall.

Try measuring the current into your heater with the battery disconnected the speed will then rise and you will come out of stall.

Let me know what current you get into that heater and the voltage across it.

You can also connect the heater in SERIES with the battery and see what current you get then.

If you have a big resistor of 2 to 3 ohms you can try this in series to the battery.

Flux

[amiklic1]

What type of non-contact tach are you using? I need one too, but it seems to be hard to find it.

Some suggestions???

[Flux]

Shadow

I have been looking at your earlier post and I see that you have tried direct into the heater and it stalls out.

Try with the heater in series with your battery, it looks as though you have a serious stall problem.

Can you post details of your prop, I suspect you have a very high tip speed ratio.

Flux

[Gary D]

Sounds like you need to open the air gap up. You need the blades to speed up with windspeed- near your designed tsr. Better to get things working the way you want now than when you put her up on the high tower. Try one turn, shouldn't effect cutin much, and then you'll have an idea where to go from there (either better or worse). Remember 48 volts should only give 1/4 the amps for the same watts (approx.)as a 12 volt system. Dan B. did this and increased amps out. Hugh has a section in one of his booklets about this too... Good luck, kill the blades before adjusting ;-) Maybe not worth 2 cents...Gary D.

[DanB]

As others said, you should be seeing beetween 10 - 15 amps in winds 20 - 30mph, possibly almost twice that on occasions.

If it is furlling, than I would think adding some weight to the tail might be in order.  It does get hard to know for sure though - especially if it's on a very short tower which would probably create pretty turbulant conditions.

The main thing that would be useful to know, is rpm vs current.  That would tell us if its a resistance problem (in which case it would be running too fast) or if it's stalling the blades (too much power at too low an rpm).  I doubt its overspeeding, and with the magnets you used and the coils you wound I'd be surprised if it was stalling too badly, but it's possible.  If it is stalling the blades I would add some resistance to the line.

I would not open the airgap, because that would sacrifice your cutin speed, which is fine as it is.

See if you can figure out how many rpm the machine is turning at 2 amps, 4 amps, and 8 amps.  My bet is it's running a bit too slow and holding the blades back.

[Shadow]

Hi Everyone, Thanks for all the input. Wind is just starting to come up, so I can do more testing today, I realize only 12 feet off the ground gonna get lots of turbulance,and lots of yawing back and forth. Just a few questions, Flux, by in series Do you mean hook heater up off the batteries as opposed to off same posts that feed batteries? And Danb You mentioned that perhaps it is holding the blades back?  What is holding the blades back? This I guess is my concern, The first dayI tried this and never realized it needed to be under load, I took readings of 130 plus volts, and the blades were just whistling around, now they seem to always stay in that 160 max range, no matter the wind speed. You can tell just by looking at them they dont vary alot in speed, the mill just yaws around a bit more as the wind speeds up. I've seen the tail start to rise but never fully furl. I'm not sure the relevence but by using the knife switch to stop it, by shorting out just two of the three phases, brings it to an instant chattery stop, never have to short out all three. This is probably normal. I think I need a better test load than a 120 volt heat element probably something closer to the 48 volt range correct? Oh and Amiklic1 the tach is OTC Stinger elevtronics, handheld digital tach,records three readings, lowest, highest and last to memory, can be retrieved later or cleared. It seems very accurate. As for correct windspeed, I use Enviroment Canada's web site for our city, updated every hour, I presume from the airport, which I am 2 miles from same elevation. Enclosed is photo of board with knife switch,rectifiers and heat sink, the posts go to battery string through 60 feet of wire, so total of 120 feet from wind generator to batterys. I connected to these posts to heat element.

[DanB]

Hi Shadow -

you said...."And Danb You mentioned that perhaps it is holding the blades back?  What is holding the blades back? This I guess is my concern, The first dayI tried this and never realized it needed to be under load, I took readings of 130 plus volts, and the blades were just whistling around, now they seem to always stay in that 160 max range, no matter the wind speed. You can tell just by looking at them they dont vary alot in speed, the mill just yaws around a bit more as the wind speeds up. I've seen the tail start to rise but never fully furl."

If that's true...  then adding weight to the tail is probably not the place to start.  sounds like the alternator is a bit too powerful for the blades here.  This could be an issue with the blades - or the alternator, but you need to bring the speed of the alternator up to match the blades.  It honestly surprises me that your alternator would stall 10' blades this badly, that has not been my experience with this setup when we use the smaller magnets like you have.  

Your cutin speed is good, so you dont want to open the airgap of the alternator.

You should add resistance to the line.  Like flux said.. perhaps putting the heater in series with the batteries would help - or... you might jsut start adding line to it!  ( a cheapo 100' 16 gage extension cord in the line might be an interesting place to start).  Whatever resistor you add to the line, will have to handle the wattage - which is why I suggest perhaps an extension cord.

Its certainly not the worst problem to have!  Much better to have the blades stalling than overspeeding, and its easily fixed with a bit of resistance.  Seems like your wasting power in that 'resistive line'... but - if you were not wasting it there you'd have to be wasting it in the stator.  Better to have the heat in the line than in the stator in my opinion.  There needs to be a certain amount of resistance with these alternators in order for the blades to be able to speed up so its really not a problem i dont think.

I should think that you should be seeing 2 amps (100 watts) at about  200 rpm from this machine.  If its making a lot more power than that at that speed its probably stalling rather badly.  Very surprising to me really....  I've made 10' machines with these same magnets and same windings and they seemed quite good, if anything I was worrying about overspeed.  I've made 10' machines with larger magnets than these (wedge shaped ones) and the same windings, and they did lean towards stalling a bit, but not badly and they worked out well.  It could be that after you get it on a tall tower, with a much longer line - that much of this problem goes away.

[Flux]

Dan

I also am amazed that this is stalling so badly on 10ft blades, I should like more details of the prop, I have a feeling that it must be close to tsr 10. I even think it may be worth trying it in delta if the connections are brought out.

Shadow

I mean you connect the pos of your rectifier to one side of the heater then connect the other side of the heater to the battery. The resistance of the heater is then in series with the load and the alternator voltage will be the sum of the battery voltage and the volt dropped across the heater. This will let the volts rise much more rapidly with load and keep things out of stall.

If you want a lot of heat and just keep the batteries charged this may be a perfectly satisfactory way to go.

Flux

[Shadow]

Ok, so far today. I checked battery voltage before starting mill, 49.2 volts. Wind is 15 mph, a little gusty ,but not bad.Started windmill,hooked amp gauge in line before battery feed. When gen got up to speed 160.2 rpm, showed 2 amps,50.1 volts.took several rpm readings highest mill got in any gusts was 162 rpm.One thing of interest I momentarily disconnected battery,and watched volts climb to about 80 plus (blades speeded up accordingly) amps dropped to zero. Then reconnected to battery bank slowing everything down rapidly,and amps climbed to about 5 then levelled off down to 2 again.After messing around out there about 1/2 hour or so batteries are showing 51.2 volts. So it seems to charge rapidly with 1 or 2 amps? I tried using a halogen light 120 volt 500 watt, it works good with the battery bank but wont run on just the mill, slows the mill down to a stop, an amp reading on the halogen light showed it was drawing about 2-3 amps also. Any of this help?..I 'll go try the extension cord thing. This heavy cable I'm using is oil feild supply. I guessed it to be 10-12 gauge, but someone pointd out it was rated for 220 volt use, that shouldnt make a difference should it?

[Flux]

considering how badly this is stalling I don't think you are going to add anywhere near enough resistance with extension cables, that would be worth a try if it was just stalling.

Go for the heater in series and see what happens.

Flux

[Shadow]

Ok, I added 30 feet of 16 guage extension cord, it didnt seem to change the amps at all 1-2 amps rising and falling with wind, but it seemed I got another 5 rpm outta the prop up 167 rpm fastest so far. Is this consistant with stalling?. Will try the heater in series next.As for the prop Flux, its a combination of Hughs and Dan's, I used Hughs instructions to build it but Dans measurements.

[Flux]

Yes that does seem to have all the characteristics of severe stalling. I am not sure if Dan has done a 48v version of the 10ft, the high voltage alternators are always more efficient and more likely to stall.

Let's see what the heater does, I think you are looking at doubling the prop speed in a 30 mph wind.

I can't find any figures for Dan's 10ft blades, can you remember the widths and drops at the various radii? I really am puzzled by this one. Hugh's 8 ft prop ought to be able to drive that alternator without stalling and I didn't think that Dan's was that much different, Dan's alternators are very similar to yours.

How thick is your stator?. From your cut in speed I suspect it is between 1/2" and 5/8".

I have a very similar alternator on test with a cut in speed of 300rpm at 24v on a 6 ft prop at the moment and that is just clear of stall with no series resistance. The prop is aimed at tsr 6.

Can you get at the coil leads to change it to delta if the need arises?

Flux

[Shadow]

Hey Flux, No I cant get at the leads, I moulded all wires into the resin. Stator is a narrow 1/2 wide, air gap is 1/8 ?. One thing that may be of some signifigance,is when I built the rotors I had one where the resin would not cure, clear to the bottom so after a couple days i finaly broke the resin up removed it all and re-cast it. In doing so I found out later I moved a couple magnets slightly so now instead of being perfectly across from each other I have one about 1/4 inch off set and two about 1/8 inch off set. I talk to Danb about this earlier he didnt think it would be a big problem but maybe its coming back to haunt me? Not sure but its bothered me almost enough to tear it apart and re-do it. But cut in speed etc is good, everything else runs smooth , just two amps is all I can get.Now Even when battery is fully charged and showing 50.9 volts wind blowing 20 mph, should it still show alot of amps going in?..Or will amps drop away because battery is full?Should the generator be consistantly producing a set amount of amps at a set rpm? I guess is what I'm asking.

[Flux]

pity about the leads, that rules out delta.

Don't worry about the magnets moving a bit, that is not the problem.

The state of charge of the battery is not going to make any significant difference, in fact in this case a high battery voltage is in your favour and will increase prop speed but the effect is so small as not to be of significance.

If you have more batteries about you could add some, probably an extra car battery if you have one to get it up to 60v may increase your current.

It's bed time for me but you can try the heater or extra batteries if you have any and let me know the results.

I keep thinking there may be something odd with the connections or the rectifier or something but it speeds up when you take the load off.

Any idea of the wind speed needed to get 48v with no load. If it is over 7 mph I would be a bit suspicious.

Just one other thought, try disconnecting one ac lead from the rectifier and run it single phase, that should speed it up, it won't do much for the efficiency but if it comes out of stall it should perform better.

Flux

[DanB]

Hi Flux/Shadow...

yes, this is quite strange and surprising.  I've made 48 volt machines with this same scheme(same number of windings, same coils and same wire gage), but much larger (2" dia X 1/2" disk) magnets and too low of cutin speed (110 rpm) and they didn't stall this badly.  (they did stall, but not any worse than this)  So it makes no sense that this thing has trouble getting over 160 rpm.  Ill insert some comments/information into Flux's posting here.

"Yes that does seem to have all the characteristics of severe stalling. I am not sure if Dan has done a 48v version of the 10ft, the high voltage alternators are always more efficient and more likely to stall."

Yes, I've seen that.  Lately its been my thinking to use slightly larger magnets on the 12 V machines (Because they seem to overspeed a touch when we use these 1" X 2" X 1/2" blocks) - the 12V ones work very nicely with slightly larger magnets.  I wouldnt expect a 48 volts stator to stall this obnoxiously with the smaller blocks though.  

"Let's see what the heater does, I think you are looking at doubling the prop speed in a 30 mph wind."

yes... that'd be interesting (Id be careful though and be prepared to shut it down quickly if it starts overspeeding so close to the ground...  that can get dangerous if your in close proximity).

"I can't find any figures for Dan's 10ft blades, can you remember the widths and drops at the various radii? I really am puzzled by this one. Hugh's 8 ft prop ought to be able to drive that alternator without stalling and I didn't think that Dan's was that much different, Dan's alternators are very similar to yours."

The blades I've been making lately are very simple - its very simplified so that we can carve them quickly with a planer.  They seem to do pretty nicely on machines up here, starting up very easily and producing around 100 watts or so in fairly low winds.  In higher winds we frequently see upwards of 1.5KW from them.

They are made from 2 X 8 boards basicly (but ours are laminated).  The tips are 3" wide, at half the radius we're 5" wide and its a straight taper to full board width (7' 6").  At the tip they are pitched 3 deg, at half the radius (where we are 6" wide) they are pitched 6 deg, and the front of the blade is a totally 'flat' plane (this side we do on a planer completely).  The thickest part of the airfoil is 1/3 of the way back from the leading edge, and the thickest part of the blade is always 1/8 as thick as it is wide.  (so were 3/8" thick at the tip, and 3/4" thick at half the radius).  It's a very simple arrangement.

"How thick is your stator?. From your cut in speed I suspect it is between 1/2" and 5/8"."

Judging from the wire he used and his cutin speed, I expect the total airgap must be about 5/8" - 3/4", his stator I believe is 1/2".

"Can you get at the coil leads to change it to delta if the need arises?"

I dont think he'd want to do that, even if he could.  It would bring his cutin speed way too high.  As it is now, his cutin speed is, if anything, a touch on the high side for a 10' prop but within reason I think.

I would be curious to know how high it is off the ground, and if there are any serious obstructions in front, or behind it.  I'd be curious if there was anything odd about the blades too.  It really seems unlikely that it should stall this badly with a 10' blade on it - and those windings, and those magnets.

I'll be very curious to know what solves this one!

[Shadow]

Thanks Flux and Danb for your patience, I'm gonna try some things tomorrow, I have a couple wire elements out of an electric furnace and one out of an old waffle iron. But ... I have a wicked argument going with my brother about amps! He says IF the batteries were dead or half dead.. I would see all kinds of amps going into them. But because they are fully charged with no load coming off I'm not gonna see any amps.  I say.. shouldnt matter this mill should continue putting amps in until the batteries boil! I told him to take his 75 amp truck alternator, disconnect the regulator on it and it will boil his battery, it wont stop charging because the battery is full. Am I not correct on this thinking? One way or other we'll get to the bottom of this, and its fun learnin! Thanks again.

[Ungrounded Lightning Rod]

I say.. shouldnt matter this mill should continue putting amps in until the batteries boil!  [...]  Am I not correct on this thinking?

You're right.

If the mill were putting, say, 40 amps into the batteries at 54 volts (about fully charged) it would, with the same wind, still be putting roughly 40 amps into them at 58 volts (significantly overcharged).

[Shadow]

 I cant leave this alone... I rigged up 2 heating coils from an old waffle Iron, together the two show about 18 ohms resistance, now I want this in series with the batteries,going through the resistance first. Now Do I put this on the positive side?..or Negative side?.Thought I read somewhere current goes from negative to positive. Is 18 gonna be two much?..I can seperate them and get 9 ohms.

[Flux]

Positive side or negative side, it doesn't matter use the most convenient.

Try 9 ohm first, if it is still too slow try both.

Dan has given the prop dimensions, is that what you have done, especially the angles.

If so I have an almost identical prop on a 20 pole alternator of the brake drum type and that produces a kW at about 20 mph.

I have to ask, but from your pictures I am pretty sure you have, is the flat side of the prop facing the wind?

Keep at it, we will crack it in the end, let's get it up to a higher speed and see what happens.

Flux

[Flux]

Shadow

Check your rectifier for shorted diodes, I seem to remember you have run it with no load in the early stages, unless those diodes are rated for a high voltage you may have killed one of them. It should have shown up on your 3 ac voltages but it is still worth checking.

You could try removing one ac lead in turn and see that the result is the same in each case.

Flux

[iFred]

You can also replace the battery for the generator, or include both.

http://search.ebay.com/amp-meter_W0QQfkrZ1QQfromZR8

http://www.ibiblio.org/obp/electricCircuits/Exper/EXP_2.html

[Gary D]

Seems you have quite a few experts helping here. Glad to see the helping spirit! I DIDN'T try to sabotage your machine by offering the suggestion to open the airgap 1/13" (1 turn). I was only trying to see if the extra gap would compensate for what seems like an extra effecient alt. Not sure of the true working tsr, I thought a few extra rpms wouldn't hurt. I understand Dan B's worry of overspeeding. Slower is better, but whatever works needs to be sometimes. Good luck, hope the troubleshooting continues... hopefully we can all learn some tricks that work! Gary D.

[Shadow]

Ok, back at it, Wind is about 18 mph,Hooked up heat element/resistor about 10 ohms resistance,connected from DC posts, positive terminal through multimeter(set on dc amps, got same readings using 0-20 amp guage) into resistor, out of resister on into battery bank, negative DC terminal straight to battery bank.Rpm of prop speeded up lots, showed 200 rpm -260 rpm. At terminals showed 50.9-75 volts with gusts. Coming out of element going into battery bank showed 50-51 volts consistantly. (element just smelled a little hotter). Amp gauge still only showed 2 amps peaking up to 3 amps tops. So by adding resistance definatley speeded up prop in lower wind and increased volts accordingly.Waiting for my daughter to get up to help determine cut in speed with just resistor hooked up.