Motor specs required for a generator. 1

[cllrdoor]

Hi,

I currently have a windblue dc 540 PMA that I would like to power using a motor. The reason for this is that I would like to determine the output of the generator to a battery at different speeds. I'm planning on using a pulley driven system to drive the generator from 0 to 2000RPMs with a drive pulley ratio of 1:2. I'm thinking I would need an AC motor and a speed controller to vary the speed. So the thing is I'm not quite certain what are the requirements for the motor to operate the generator. Any help would be greatly appreciate, thanks.

 

[jraef]

Power is power. The pulley system plays no part in it other than robbing some effiency, all it does is change up the speed / torque relationship. If you want to run the generator at peak power, determine what that is and figure your motor must be at least that size plus whatever losses you have in the pulley and drive system. Duty cycle may play a part in that if you only need peak power briefly, you might be able to get away with a slightly smaller motor.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[waross]

Do some self educating on the characteristics of batteries, particularly charging currents and voltages.
A small battery will take more current than a large battery. A dead battery will take more current than a charged battery.
Try a 1/4 HP or 1/3 HP three phase motor and a VFD suitable for single phase input. If you find a 200 Volt or 208 Volt rated motor at 1760 RPM the VFD will be able to drive it to 2000 RPM.
Try different sized batteries at different states of charge.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cllrdoor]

Thanks, for a quick response. Assuming the generator will produce anywhere between 36 to 1800 Watts at peak power for a specific operating speed it would require 2.25HP and probably double that in order to account for any losses (or is that an extreme). So the best choice would be a 5HP motor. Is my thought process correct, I'm just wondering because a 5hp motor is pretty pricey but if it's whats needed, oh well.

 

[jraef]

Looking at the specs on that little generator, it says it's peak output is 15A @ 12VDC when running 2000RPM. That's 180W, not 1800W.

I would just go get a good quality variable speed drill motor and be done with it, at least it's good for something else afterward.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[cllrdoor]

True, it would probably be the fastest/cheapest way to do this. Thanks.

 

[GearlessGenerator]

Dear Cllrdoor.

For a motor to act as generator it should outputs about 1.2 the rate power at when it is driven at 1.07 (107 percents) the synchronous RPM.

FYI: There are many efforts to lower its synchronous RPM using VFD (variable frequency drive) let's say to 100RPM . . . . and . . .then using the prime force (wind turbine) to drive it to 107 RPM (107%)- Theoretically it should act as generator, but somehow it does not work that way. For centuries it stay as a challenge for the community to find the way to operate a motor in generator mode at low speed. You may take a look at:

http://www.philica.com/display_article.php?article_id=316

. The article presents circuits allowing one to do just that.

Good luck!