New 1.3 KW DC Servo motor for $75 - is my math correct?

[Matrix1000]

I picked up this motor off ebay the other day for $75 because it looked like a big amatek servor (25 lbs) but I'm not sure exactly what I've got yet. When I hook up a 100 watt light bulb to it and spin it fairly quickly with my cordless drill it lights it up about half way.  

When I then stick it to my little volt/amp meter and try to measure amps it just about twists the drill out of my hand.

So I'm not sure what exactly I am dealing with yet

The label says it is 180 volt 73 amp motor so would it be correct to go

180 volts x 73amps = 13140 Watts or 1.3 KW?

If thats true why won't it light a standard 100 watt light bulb all the way at pretty good rpm's but turn fairly easily.

I'm wondering just how big of a turbine blade I'm going to need to turn this thing, I just wanted to put a jerry blade on it but now I'm not so sure if that would work.

Thanks for any advice.

[Matrix1000]

[Dan M]

If it's 180v 73A then your math is correct (13,140 watts).  Your metric prefixes may need a little work, thats a little over 13Kw!  

As for the lightbulb, if the motor was designed for 3600 rpm (at 180v), and lets say you were spinning it at 1000 rpm with the drill, voltage (in or out) is fairly linear with respect to rpm.  If this motor (generator) was good for 180v at 3600 rpm, then you were getting about 50v at 1000 rpm (half-lit lightbulb).

At the rpms you can get using it as a wind turbine (lets say 500 max) you'll get around 25v.  If you can find blades to spin it that fast and still pull 60-70 amps you can get 1500-1700 watts.

You may want to talk to some of the other guys here about re-winding the rotor (it looks like it has brushes so I assume the rotor has the windings).

-Dan M

[DanB]

The limitation is always the current.  So how much power you can get from it depends on the voltage at which you take it... and to get higher voltage, youll need to run at higher rpm.  But... for constant duty - it's rated 15.7 amps.  Perhaps you could take 20 amps or so continuously... because it would cool a bit better up in the wind.  It's rated 180 volts @ 3500 rpm.  So it might make a nice small wind turbine @ 12 volts... I would expect you might see 18 volts ( perhaps a bit less) @ 350 rpm, and 12 volts at a bit over 200 rpm.  And I think you can expect it to hold up to 20 amps pretty well up in the wind, you might see "peaks" of twice that or more at times.  Not a bad score - much more powerful than most ametek motors, and  it would work nicely with a 6' prop.  It might make a nice 200  - 300 watt, 12 volt wind turbine w/6' prop, that would be my guess.

Whenever looking at motors like this - the current rating (amps) is what you need to consider.  In this case... about 16 amps - and I think you can usually push that a bit, so call it 20 amps.  20 amps * 14 volts = 280 watts, thats the sort of power I suspect a motor like this could produce @ 12 volts continuously.

[Dan M]

Sorry, I replied too soon, I didn't wait for the spec tag to load.

If your max sustained current is 15.7 amps, then you've got a potential of around 2.8kW at 3500 rpm.

If you load it with more current that this (either as a motor or a generator) for more than a short time things will cook.

If you can spin it fast enough to get 25-30 volts, and load it to around 15 amps, then you can get 400-450 watts.

-Dan M

[Matrix1000]

Thanks!  That is a big help

[Jerry]

Hi Matrix

The closest thing to this motor I've tested is a Nortictrac (sp?) 2.5 hp, 130 volt, 17.6 amp, 3050 rpm.

I used a 49" tip to tip 3 blade Jerry blade with Mike mods. Here are the test #s as gathered from a wind test in my S-10 pu. this was a 12 volt test.

   10 mph 2.5 amps

   15 mph 5   amps

   20 mph 10 amps

   25 mph 15 amps

   30 mph 32.5 amps This was at 14.5 volts for 471.25 watts.

I make a compairison to the  SW Air-403 wich is rated 400 watts at 28.8 mph.

The diferance between the 403 and the tred  mill genny are. Sug. reatail on the 403 is over $600. tredd mill motors are chep. My 403 doesn't do any thing till 13 mph. Tred mill genny shows an amp at 7.5 mph. The 403 can be extremly noisy in high winds.

My blades are very quiet.

For these motors there very high RPM ratings hinder there low wind output but for the price the power they do and the small amount of work you do to make a genny of these is great.

I suspect that yours will have a littel better low wind power than mine since it has a higher voltage rating. Our amp ratings are very close.

So now through some blades on that thing and make some power.

                      JK TAS Jerry

[Jerry]

PS heres a pix of the above genny.  JK TAS Jerry

[drdongle]

Jerry did you use the original flywheel/pulley for this conversion?

Also does your chart mean that you didn't generate 14.5 V till it reached 30 mph?

if not at what speed did it start generating enough voltage to charge a 12v battery?

Carpe Vigor

Dr.D

[Jerry]

Hi Dr D.

I removed the flywheel. I didn't track voltage on this one till 30 mph. Sorry.

I did see charging curent at about 7 mph. I'm left handed. So imagin this. I'm driving the S-10, looking at the speedomitor, looking at the amp meter, looking at the volt meter and trying to not crash at the same time and I can'tr write right handed.

I go alone on these wind tests. This is why I'm gathering parts for my wind tunnel.

I'm putting up a 1,000 LB 40 FT free standing tower on sat. morn. so after that comes the wind tunnel project?

                              JK TAS Jerry

[drdongle]

You have space for a wind tunnle? what will you use for a power source, V8 engine?

Carpe Vigor

Dr.D

[Jerry]

Hi Dr D

I have room for the size wind tunnel I need. I thinking the inside opening will be 6 ft square. This is big enough to test my small blades.

The power will come from four 2.5 hp 3050 rpm dc. tred mill motors. I will be able to vary there speed from 0 to as fast as they will turn with the 24" 4 blade industrial fan blades I have. There will be 14" concrete tube forms 2 ft long in the center to correct for turbulance.

The tunnel will be 12ft long. There will be meters for MPH, VOLTS,AMPS. The hole thing will be built on a trailer frame so it is portable. It will have batteries on board for both powering the blower motors plus providing a load for the wind genny under test.

I'll do a post when its under way.

                            JK TAS Jerry