Alternator troubleshooting 4

[grreen]

I have an alternator, output 14v 165 amps at 7000 rpm, which I attach to a vertical axis wind turbine shaft with speeds of 200 to 250 rpms. I installed the new alternator in and I did not get a reading even thougg gust winds of 60 mph were present, no voltage no amperage....
This altr. is bidirectional.

My q's is if its the difference in rpm from the shaft that need to be mounted to a step-up gear box of some sort?

thanks.
wind-no power, NM

me, you; us.

 

[itsmoked]

grreen: Sounds like fun!

Yes you need to spin that baby at least 2000RPM. 3000-4000RPM would better. Also you may need to provide 12VDC to excite the alternator so it can start generating.

Consider using large and really large V-belt sheaves to get your gear ratio. (Larger sheaves are more efficent.)

 

[mc5w]

Just as long as the sheave on the alternator is not too small for the big sheave on the wind turbine. You need to have at least 120 degrees of contact between a V-belt and a sheave to transmit significant power.

You need at least a 15:1 speed increase in your belt drive and that might be easier to do by cannabalizing the double reduction belt drive in an older clothes dryer. What you want are the large and small sheaves and throw away the existing intermediated shaft because that uses sleeve bearings. What you need are tapered roller bearings for your shafts.

 

[ccjersey]

Even if the alternator is "self exciting" (commonly called 1 wire alternators), it is best to arrange a flashing connection from the battery unless the alternator will always rev up to high speeds whenever it is started, like on a generator or pump engine. On a machine which starts slowly, the alternator may never excite.

Even if it revs up enough, it may loose the residual magnetism between infrequent runs and need flashing. What brand etc of alternator do you have?

Jim

 

[grreen]

thanks for the posts. I guess the altr. will work with a battery to get it started, but the whole idea is to have it generate on its own.

re:"You need at least a 15:1 speed increase in your belt drive and that might be easier to do by cannabalizing the double reduction belt drive in an older clothes dryer. What you want are the large and small sheaves and throw away the existing intermediated shaft because that uses sleeve bearings. What you need are tapered roller bearings for your shafts"

I will look for this set up, seems that this will work to have it reach its rpm, now I wonder what wind speeds Ill need to reach the desired torque.

thanks, Im out in the hunt for an old dryer.

 

[stardelta]

165 amps at 7000rpm?? are you sure?? An alternator capable of delivering that sort of current and capable of operation at that speed would be massive to say the least. I suspect from the details quoted that what we are talking about is an alternator designed for automotive use and the 165A you quote is more likely to be 16.5A. Some things to consider, firstly such alternators are not designed to be run vertical and prolonged use will have a detrimental effect on the bearings. Secondly if gearing up you will need to increase the overall power going in and the only way to do this will be to increase the size of the fan. Bear in mind also that gearboxes are generally designed to transmit power/torque when reducing speed and not when increasing speed, this again could have a detrimental effect on the gearbox if used in this manner. I would estimate a fully loaded automotive alternator would require at least 2hp to spin it at constant 7000rpm and a lot more to accelerate it up to that speed from standstill, plus maybe another 1/2hp would be lost in the gearbox and belt drive due to friction and maybe oil-drag. I am sure some of the more academic types in the forum will be able to provide relevent formulae relating to fan design and do the maths (unlike me)but I think the size of the fan needed to generate the required input power at 250 rpm will make your project unfeasable. I would be looking for a machine capable of generating at the fan speed you mention although I doubt one exists and using a torque converter between it and the fan, this wont make it any more efficient but will make it easier to start rotating and to get up to speed.

 

[OperaHouse]

Check out

http://www.hydrogenappliances.com

for their system of a knurled shaft riding on a tire. They say it is simple and it works. They sell a PM "car" alternator which is a better idea. While you can make it work, standard car alternators for a wind generator are basically a bad idea.

 

[ccjersey]

You will need a battery bank for any useful system of DC generation. The alternator will output a "DC" voltage with a significant voltage ripple that won't do anything any good on the downstream side. The battery will damp this out and also allow you to apply loads greater than the output of the alternator at that instant in time.

The tire and knurled shaft sounds like it could work. Any machine shop could knurl a shaft for you or make a knurled extension to fit over your alternator shaft. You would probably need a bearing to suport the end of an extension over a few inches long. You could use a durable tire with a smooth surface maybe like an airplane tire, forklift tire or golf cart tire to run it with.

I haven't seen a dryer mechanism like that before. Wonder what brand you would need to look for?

Jim