PM DC Motor's from press dampening systems

[Devo]

I work at a printing company ,the presses use PM DC motors on the water systems in the last year they have replaced about 10 , which I take home & about 2 thirds of the time the brushes are dirty..

Anyways I have put an old steel barn fan on 1 & bolted it to the picnic table to see what they produce.

I get about 30 - 40 volts DC depending on wind speed & 1/2 to 3/4 amp

I am lacking in the electrical field :-) is there any way I can take the output & cut the voltage in half & double the amperage for a 12 volt system?

I am thinking of having a few running for camping into  a few golfcart batteries to run some lights & stuff at night

Thanks

Devo

[Ungrounded Lightning Rod]

How are you checking the current?  Are you measuring it at the same time as the voltage, using a resistive load, or measuring open-circuit voltage and short-circuit current?  If you're measuring short-circuit current you're probably stalling the fan.

How is the fan hooked to the motor?  Mounted on the shaft, or belt-and-pulleys?

What's the rated current on the motors under normal load?  (Try not to go over that.)  Better yet, please post the whole list of ratings off the plate on the motor so we know what we're dealing with.

Try hooking the fan to a 12V battery or two in series for 24V (through a blocking diode) and measuring the current then.  You might just find a LOT more than a half-amp when the battery is holding the output voltage to 12 or 24 and the wind wants to drive it higher.

If the series resistance of the wind is too high to get a decent current you can use a down-converting switching regulator to trade volts for amps.  Or you can rewind the armature (a pain in the tail, and you still won't have brushes designed for it).

If the series resistance is low enough, and the current ratings high enough, that you can get a decent current without frying the genny it's just a matter of getting the speed right.  You can do that with gears, belts-and-pullies, or by designing a set of blades with the right TSR.

[Devo]

Thanks for the reply , I test the voltage first with a regular volt/ohm/amp meter

It has creeped up to 50 in a high wind.

then i put the meter to dc amps , the meter max's out at 10 , I get about a half amp & the fan slows.

It is a small dc gear reduced motor , I took the gear reduction off & ran an old barn cooling fan direct on the shaft.

here is teh info off the motor

Bodine motor company gearmotor (chicago)

S/N   -B1090B0061

TYPE  -33A3BEPM-5R

VOLTS -130

HZ     DC  FF/1.0

A      -.75

HP    -1/12

UF    ///////// INS -B8

TIME  -CONT

RPM   -50

TORQUE -45LB-IN

RATIO  -40-1

I have run it direct into a marine battery it will drop the voltage to the battery which is week - 11 & slwoly charge it , if the wind dies the battery turns the motor

as I haven't put a diode in line yet(maybe today)

I am also working on hand wound wind gennies just thought for a small camping battery charger these may work & I can get plenty , I also have a few dc motors that used to be used in the old days to run the power to the conterveyors.

Devo  

 

[Ungrounded Lightning Rod]

I test the voltage first with a regular volt/ohm/amp meter

It has creeped up to 50 in a high wind.

then i put the meter to dc amps , the meter max's out at 10 , I get about a half amp & the fan slows.

OK:  You're measuring the open circuit voltage and the short circuit currnet.

When you're hooked up to a battery to charge it the voltage will come down to the battery's votage - partly from resistive drop, partly from the load slowing the fan blades.

When you hook your ammeter across the motor you're shorting it.  So it acts as an electric brake.  This slows it WAY down, and causes the blades to "stall" - the airflow detaches from the backside of the blades and you get much less force on the shaft (and thus much less current out of the genny) than if the blades were turning.

Hook your ammeter in series with the genny/battery/(diode if you find one) combo and measure the current that way.  This will give you charging current.  That should be significantly better than what you were seeing so far.

A 130v 1/12 horse motor is rated for about 4 1/2 amps - and with it in the wind you could probably run it up to 5 or maybe a bit more without frying it.  The rating also applies to the brushes and their wiring so you might get reduced life or burnout if you go much above that.  (But I wouldn't panic if gusts take it up to 10 for short times.  Seems unlikely though - I'd only expect a couple amps from this.)