stepper motor generator

[sudipto]

I intend to make a wind power generator and have got myself a stepper motor which is rated 3.3v and has 10 wires of different colours. I have identified 5 pairs each of which give about 24 v readings and each can light up a 10w led.. Please advise how to make this fit for charging a 12v car battery at a reasonable rate.

 

[blueroomelectronics]

What do you consider a reasonable rate? Days , weeks?

 

[sudipto]

thanks for the reply

By reasonable i mean the maximum current [amps] i can get keeping the voltage just enough to charge the battery. Oh yes, here is all that it says on the motor label.: 'Step Syn' TYPE - 103-89573-5011 DC 3.3v 3A 0.72 DEG/STEP -lot no etc. SANYO DENKI CO., LTD. JAPAN. The volt reading says about 13 to 19 just by rotating the shaft by hand. but is not showing any amps like whenever i attach it to the amp meter it says 0.00 but it lights up the 10watt lamp properly which usually needs about 1 amp current and 12v to run.

 

[helpmonkey]

how big is that motor ... im not sure you are measuring the output correctly ... a 10watt LED?? ... 1watt would require over 3amps from a 3.3volt motor ... to charge a car battery (assume the car bat has 100amp/hr capacity and is completely discharged) you would need to provide 1amp at 12 volts (12watts) for 100hrs ... so if you wanted to charge the battery in a day (24hrs) you would have to feed it 4amps at 12 volts or 48 watts of power ... your motor if it put out 10 watts (which I really dont think it would) would require 5 days to charge the battery if it were spinning at optimal RPM continuously.

 

[Simple Simon]

The best way to check a motor for output, is to chuck it in a lathe or drill press. That way you will have outputs at known RPM. Test should be taken with a battery at about 1/2 charge.

startup voltage should be 12volts at 150 rpm. (Cut in speed)
Most wind generators will run up to about 600 rpm. the voltage should then be about 20 volts, "D.C." (if you are charging a battery).

Your motor is rated at 3 amps. So 3 x 12 volts = 36 watts. Your first build should be something small, as it will be a learning experence. 3 amps into a 100 amp battery will take about 30 hours to charge.

S. Simon

 

[tcmtech]

Being its a small wind generator you are building you can go with crazy high RPM's well into the thousands and not have problems or be running at unreasonably high tip speeds.

On the stuff I build I consider 600 RPM to be a good top end for a blade set of around 12 feet in diameter or less.

 

[sudipto]

thanks all --- Yes it is a rather large motor. It is exactly 9inches long without the shafts [about 2 inches on either side] the dia is about 4.5 inches and it weighs about 11 kgs. I don't really know the application of this motor but the recycle shop guy said it probably was from some cinema equipment. I have built myself a cradle for it out of some steel strips welded together and on the shafts, which luckily are same dia as bicycle pedal shafts, I have attached a pair of the same. The readings i am getting are based on the normal pedaling speed of a bicycle, which i do sitting on a chair. I have done some trial and error on the 10 wires which are [i have paired them as the generate power that way] yellow-pink, green-orange, blue-white, black-brown, and red-gray. each pair can light up a 10 watt led[which i recently bought on ebay] I have also tried shorting the yellow-green-blue-black-red and also orange-pink. And with these two I seem to be getting the maximum AC ampere. I even tried lighting a 35w 12v bulb and it lights up just about 25% less bright than using a 12v car battery. What I need help on is a) whether all that I have done till now is right and b) how do I go about converting this current into DC. The net is full of circuits for stepper motor wind power converters - thing is they all mostly talk about 4 to 6 wires coming out of the stepper motor. like this Make A Bridge Rectifier From Diodes - Wind but none of them show how to scale it up to a 10 wire motor. So is there some simple logic for doing this. I am wary of the fact that on one hand I may ruin the motor and on the other [more likely] will end up under-utilizing its capacity.

 

[sudipto]

the motor looks like this

see attachment

 

[sudipto]

have posted a detailed report but I think it is in the moderation queue

 

[sudipto]

Ok looks like my detailed post got lost somewhere. well The stepper motor in question is large. about 9 inches in length[without shaft] and 4.5 inches in diameter and weighs about 11.5kg. At present I have built a cradle for it bade of welded steel strips and attached a pair of bicycle pedals. The colours of the wires that come out of it are yellow-pink green-orange blue-white black-brown red-gray. Now I am getting about 14 - 19 volts and probably about 20 watts of current. What I have also tried is joining together the yellow-green-blue-black-red and the pink-orange and between these I am getting a higher ampere may be about 30 watts. I found a whole lot of circuits for bridge rectifiers on the net but most of them are for stepper motors with 4 to 6 wires. What I need help with is how to scale this up for 10 wires and get maximum ampere.

 

[SABorn]

You can use 5 bridge rectifiers and connect 1 wire from every coil to one of the AC inputs each.

Then parrallel connect all the negatives together and parrallel connect all the Positives together.

Now you have all the AC from the 5 coils converted to DC with a + and - terminal.

Spin it and test volts again , this time you should be able to also test amps.

The problem with stepper motors for wind generators is they have a very high cogging effect and normally take a gail force wind to get them to start to spin.

There is no easy way around this as a bigger blade set will give a lower top rpm, and then you also have the problem of controlling the generator in strong winds with large blades.

 

[blueroomelectronics]

Try spinning it with a load attached. It's going to be difficult to turn.

 

[sudipto]

Thanks SABorn, that helps. I am trying to make a vertical turbine with hinged sails to increase torque. Hope it works. However I have a question 2 : is any way i can spike bust the power at the AC level itself. Because my project 1.2 is to create this slow rocking swing coupled to a windmill connected to the stepper motor which will have led lights connected around the whole property. this way i will be able to get loss less transmission which is a problem with DC. So is there a possibility of getting some power backup for say a few seconds at least.

 

[tcmtech]

Thanks SABorn, that helps. I am trying to make a vertical turbine with hinged sails to increase torque. Hope it works. However I have a question 2 : is any way i can spike bust the power at the AC level itself. Because my project 1.2 is to create this slow rocking swing coupled to a windmill connected to the stepper motor which will have led lights connected around the whole property. this way i will be able to get loss less transmission which is a problem with DC. So is there a possibility of getting some power backup for say a few seconds at least.

Can you clarify all of that considerably more?

 

[sudipto]

OK' is there any way I can harness usable power from a stepper motor WITHOUT converting it to DC?. As you see the motor generates enough power to light about 20 watts of led without conversion. And the transmission of this power say through a normal electric wiring of 20 - 30 feet is without loss.

 

[tcmtech]

Okay lest put it this way what are you talking about when you say,

is any way i can spike bust the power at the AC level itself.

And

Because my project 1.2 is to create this slow rocking swing coupled to a windmill connected to the stepper motor

And

the stepper motor which will have led lights connected around the whole property. this way i will be able to get loss less transmission which is a problem with DC.

What is spike busting power and where or how do you come to the conclusion that you need AC because DC incurs looses plus I have no idea what "slow rocking swing coupled to a windmill connected to the stepper motor" possibly refers too either.

 

[SABorn]

First of all forget working with AC, as with wind turbines we often reffer to it as "wild AC" because it has no fixed frequency and the best way is to rectifie it to a stable DC.

Now the voltage will fluctuate with RPM so you need some way of controlling this, and the best way is to charge a battery as it will keep load on the mill and give a stable voltage to work with.

Then you need some way of controlling the charge to the battery, so not to over charge the battery, this can be done with a simple opamp circuit.

Then once the battery is charged you need to divert the power to be able to control the mill, as you CAN NOT just disconnect the mill and let it spin free, it will self distruct.( known as a run away mill)

The best way is to divert the power to a DUMP load, and this is normally some form of heavy resistor capable of handling the power produced under all wind conditions.

Another way is to simply short out ALL the AC leads and hit the brakes so to speak, this can have problems with iron core machines (as a stepper is) as the iron core can saturate and the mill over speed past the point of control.

The first rule of building a wind turbine should be looking at how you will control it in all wind conditions, as this might largely effect how you go about construction in the first place.

It has been noted and tested on many forums that wild ac can have larger losses over wire distances than DC.

Personally i dont like VAWT's (vertical axis wind turbines) as they are a ineffecent design and are around 10 time less efficent with extracting energy form the wind compared to a HAWT.

You have a lot to learn about wind turbines and their use, but we all start somewhere and learn as we go, but remember short cuts will result in large failures with wind energy.

Many of us have played with wind energy for a long time and often have learn the lessons the hard way, and its a sad feeling seeing your mill scatted all over the yard and will scare the **** out of you when you see a runaway mill in good winds.

 

[sudipto]

Thanks! I think I have all my questions answered. OK I give up the idea AC system. However I have an idea for a more efficient VAWT. I am enclosing a plan view. tcmtech - I will soon be posting a drawing on how I plan to couple a swing to the wind turbine.

 

[SABorn]

I look forward to seeing your plan.
But a important thing to remember is the most efficent turbine is a 1:1 ratio of mill to generator and every introduction of linkages and gearing of any style will introduce instant losses.

As you were concerened with a tiny loss in the wiring, then you will have much greater losses in design if you incorparate linkagaes or gearing even belts and chains cause big losses.

Please test and see for yourself.

 

[sudipto]

In a HAWT does the generator have to be perched up at the height of the axis? In my case the axis needs to be about 18 feet high to get some decent wind. And the stepper in question is about 11.5 kg net. So is there any site where I can get proportions like fan dia, no of blades etc.?