stepper motor generator

[tcmtech]

Being you have a 5 wire stepper motor you most likely have the 5 wire unipolar winding configuration as shown here.
For that you would need 8 diodes. Two on each phase end.

Also being you have a smaller system I would possibly consider carving blades out of a good clean piece of 2 x 4. All you need is a basic saw and a belt sander or some time and hand tools.

Basic wind generator blade shapes are surprisingly easy to make yourself. I and a friend of mine have made many blades out of 2 x 4's and 2 x 6's that lasted for many years unprotected and ungoverned.

The biggest blade failure issues I had was when I tried buying supposedly good quality fiberglass blades online but so far its been a total waste of money. Every set has failed while working in the same service as I have had cheap homemade 2 x 6 blades running in. Plus a few where junk designs that had near zero starting torque and overall poor efficiency despite what the dealer rated them as.

For what you have I would probably run a 4 - 5 foot two blade set made out of a single 2 x 4 or a three blade set made out of three pieces of 2 x 4. The odds are they will never spin themselves apart at that size if the roots are properly bolted down.

As far as homemade single piece two blade designs go have I personally had several sets made out of a five foot long 2 x 6's that would regularly spin up well past 4000 RPM with out damage! Thats equates to a 714+ MPH tip speed which is pushing into the supersonic range which gives you an idea of how fast you can spin a common piece of pine board and not have it rip apart.

 

[SABorn]

4000 RPM is just plain stupid in rpm for a windmill sorry to say.

400 rpm is a more realistic upper speed and 1000rpm is to high as far as im concerned.

A good alternator should make power from 100 rpm to 400 rpm and be furling after that.

In most cases there is a limit with rpm that you will receive no more power from the alternator regardless of increased rpm.
It is dangerious and destructive to allow the mill to go beyond the rpm it stops producing power at. (a runaway mill)

Design it right and get the furling correct and you will have a very reliable and safe mill, do it wrong and you will burn the alternator out, or will scatter the mill across the yard, if not even kill someone in the process.
Never under estimate the power of the wind, and have control measures like furling in place to handle the conditions.

 

[tcmtech]

Actually a working range of two thousand RPM is not that fast on a small blade set if you factor in tip speed ratios to working wind speed range. Many of the old 6, 12, and 32 volt winchargers from the 20's and 30's ran 6 foot two blade rotors with air brake governing systems that didn't kick in until 1200 RPM or higher. A friend of mine has a original 1930's 5 foot one that won't trip until around 1800 RPM.

I have a few of those original 6 volt units along with an old Paris Dunn 1.5 Kw 32 volt that when it had its original 9 foot blade ran up to around 950 RPM before it tipped up out of the wind to regulate itself.

The point I was making is that simple home built designs can fly way past the typical speed ranges without problems if done properly. I am not saying that they all need to run at supersonic tip speeds but when you know they can take that level of abuse anything less is no concern.

For what its worth though I have been flying small blade sets at those speeds for around 20 years now and so far weathering and leading edge erosion was the only thing that took them out. It wasn't until I started taking others advice a few years ago to slow down and use better blade materials like whats used in the factory made fiberglass units, that I started having blade failures left and right so for me its back to home built wood blades with no top end speed limits on the smaller ones.

 

[SABorn]

Windchargers like this........

7-23mph wind operation.

 

[bryan1]

All good information for you sudipo in above posts, now what diameter is the output shaft on the stepper? That will dictate the size of blades you can put on it for a decent life as a wind generator. The smaller the blades the faster they will go unloaded and bog down when loaded. Larger blades will provide more power and will spin slower, this all depends on your setup of course.

Before I would get too excited about using that stepper as a wind generator if I had it, I would do a static test in a lathe or similar device to testout the average that stepper can do into your batteries. I can't see the point of going thru the whole process of building the infrastructure needed ( tower, generator mount, furling tail etc) until I knew what that stepper can output. Why go the effort if your only going to have a 100-200 watt wind generator.

Like I've said above go do a static test and provide some hard figures here of the results. Myself and others will be happy to help if those figures prove worthwhile. It is in your best interest to test this stepper motor first as it may or maynot be suitable. Only a static test will prove it.

Regards Bryan

P.S. As your location isn't filled in your profile we don't know where abouts in the world you are either......

 

[sudipto]

thanks for all the information and thanks tcmtech for the link. tcmtech - could you explain the 2 x 6's and 2 x 4's as i am new to this field. Oh yes I am from India [Asia] The place in concern is a suburb outside Bangalore city. It is not exactly a windy area but you get averages of 5 to 10 mph at different times of the year. bryan1 - I will do a static test soon and post the data.

 

[sudipto]

The stepper motor has shafts on both ends each about 1 1/2 inches long. One is about 5/8" dia and the other about 1/2" each has two milled out flat surfaces for tightening of bolts. Thicker one has a collar about 3 1/4" long and about one and 1 3/16" dia. This collar has threaded holes of about 5/32. The thicker shaft is also on the same side of the motor which has holes for mounting bolts drilled on the square flange.

 

[tcmtech]

I was referring to common structural lumber dimensions. In my part of the world this numbers refer to wood of the common 2 inch by 4 inch or 2 inch by 6 inch dimension.

Given you have light winds you could run a fairly large blade set being you have a 5/8 inch shaft to work with. The general rule for blade to shaft sizing is approximately 1/8 inch of shaft diameter for every foot of blade diameter. So for the most part you should be able to safely fly a set of blades 5 feet across without concerns about twisting or damaging the shaft on your stepper motor.

Its just a thought anyway.

 

[sudipto]

I have access to this redundant training airfield where i could pick up a junked 5' prop and do some repair job.

 

[be80be]

I have a stepper I've played with A little It's HPM-215-24A . It's rated at DC 24 volts .32Amps 1.8DEG/step

At about 200 rpm it puts out 24 volts. At 1300 rpm it hits 98 volts. Thats as fast as the drill I have it chucked in can go.
It don't even look like it was going to top top out as voltage goes.

I don't think you'll have to worry about the blade more like the stepper melting down at high speed.
Because my little stepper would be hitting the 100 watt range at 1200 rpm and it was only made for 25 watts

 

[sudipto]

hi tcmtech; it is a 10 wire stepper motor not 5

 

[be80be]

It's a 4-Phase stepper

 

[tcmtech]

I have access to this redundant training airfield where i could pick up a junked 5' prop and do some repair job.

Sorry but a airplane prop makes wind and a wind generator prop catches wind. The aerodynamics concepts are sort of mirror image backward from each other. But it the aircraft prop will give you a good idea and understanding of why and how airplane props are able to be ran at thousands of RPM''s without ripping apart. They have massive roots at the center where as low speed wind generator blades tend to have small and weak roots that shear off or rip out if spun at high speeds.

If you carve your own set you basically just need to copy the aircraft prop but change the pitch angles so that it catches wind instead of produces it. You probably wont make super efficient one on your first try but its a good way to learn how they work by doing!

 

[bryan1]

Hi Sudipto,
For most guys making their own blades **broken link removed**
is what most use as a general rule for making blades. The calc already some some figures in but put in your own to suit and it will give you the best profile to make.

Regards Bryan