Why do they use the number 4 on DC motor/generators

[(unknown)]

I need a 48v generator for a win-gen.

I found a 4z266e Dayton PM motor. Old stock, but new in the box.

Rated 2500rpm, 180v, 11.5 amp, TEFC, Reversible

I guess the weight to be about 60 pounds.

I've read that dividing by 4 would give you the rpm and voltage it would begin to generate. Why 4?

How would I calcuate the size of rotor to be used?

I live on the border of a class 1 and class 2 wind zone.

Thanks for your ideas and wisdom,

Bill

[ghurd]

Not sure what you read, but you must have misunderstood it or it was just wrong.

A 48V starts charging at about 52V?  Depending on the battery voltage.

So 52/180 gives the percentage, and x2500 gives the 52V cut in RPM of 722RPM.

That's awful fast for something that size.

A 1750RPM 180V would be 500RPM.  Still awful fast.

Can't be completely sure what a motor will do until it's tested.

Might try to find a 180V 1000 or 1200RPM motor.

G-

[BilljustBill]

Thanks for the insight.  

This motor has a double-ended shaft.  The Ebay blades are made with carbon fiber and taper.  What I'm thinking is using a six-bladed hub with 64" blades on the front.  Then, with the motor on the center of the pivot, and using the rear shaft with a spline connector, I'm running a 70" set of the same type blades with a 3' long shaft supported with ballbearing pillow block bearings connecting the rear motor shaft and rear blade shaft.

With the larger diameter of rear blades 3' downwind of the center point, they act as the tail and keep everything pointing into the wind, and should almost double the rotor power with high speed blades.  The higher RPM isn't going to be a problem with these blades.  I'm just concerned to know if there is enough rotor area to be able make the 48volts and higher amps.

Bill

[ghurd]

That 700RPM cut in is going to be a problem with 6' dia.

The Air-X knock-offs look designed for 3.  6 will slow them down.

Adding blades on the back is not going to help much of anything either.

G-

[BilljustBill]

With that large a PM motor/generator, I was concerned about power to spin it rather than high RPM.  The rear rotor is getting a disturbed wind flow, but being 6 bladed, I'm thinking it would add some addition power to the front rotor to spin against the generator load rather than cause more of a drag effect.

Because I'm in a lower wind zone, I'm needing power on the low end of wind speeds.

It appears that these blades can handle high speeds.  Other than tilting down the tower because of a severe storm, as long as the PM generator has a load, I'm thinking that furling or braking may not be needed.

What do you and others think?

[ghurd]

Just me, 6' and 700RPM are not suited to each other.

More so in a low wind area.

Adding more blades only helps if they are designed for more blades, in which case using less blades would be subtracting blades.

Look at Alton Moore's calculator.

Power to spin is a catch 22.  Or catch 44.

Power to make speed is like open voltage watts.

The motor in my car can spin 12,000RPM.  How fast can it go?

The car is blue.

A smarter man than me said anything over 3' dia should be a furling design, and I believe him.

Brakes fail.

G-

[BilljustBill]

With my rotors being 6-bladed and the vendor saying they will operate safely at 700 rpm, I trying to hook together what data I've found to make this 48v generator.

Here is the sight that might help with some of the data I've found.  What do you think?

http://windynation.com/web/choose_a_motor

[ghurd]

I won't speak for the safety of the blades at 700RPM.

That 722RPM is when it starts making 5W.  Not the RPM it will always operate at, or the max RPM.

How strong will the wind have to be to reach 722RPM with 6' dia?  Strong.

My rough guess is it will not reach charging voltage until 10~14MPH (without the rear set of blades).

Adding a second set of blades behind the first set is going to make it worse.

Guessing a 6-blade set of those should be on something with a cut in voltage at about 225RPM.

Speaking in generalities, with Ameteks as the example (should be able to find a lot of related data).

Most people say try to find one with cut in voltage between 300-400RPM, say 350RPM.  Because that is well suited to 4' dia blades.

People who buy one with a cut in voltage of 500-600RPM have a fit when it almost never reaches charging voltage, and they need to shorten the blades.

Now relate that to your proposed system.  

The cut in RPM is over double a decent Ametek.  

And the blades are longer (meaning less RPM).

It would be workable with a 12V system, but that is an awful lot of mass and size for 150W peak.

G-