using PMA 3-phase servo motors for VAWT

[lakesidepark]

I have been making plans for a while, and just now moving to actual construction of some small vertical turbines. For now that's the limit, but future may include some larger scale and even a HAWT. The two current plans are a sav (target RPM 60 - 80) that will have wings later to push the RPM (maybe) to 100.

I have a good pile of servos from discards and teardowns. These are all 200V 3 phase 1500RPM continuous duty motors with wattage rating based on the 1500RPM maximum. Sizes are a 450W (two), 850W (two versions of this), or a 1.3kw. The profiles and construction are similar. With the original configuration, a rough estimate is that any one of them will make 14.1VDC at 75RPM after rectification (5% of 200V = 10VAC*1.41 = 14.1VDC). A couple of bench tests with one phase rectified affirmed this. Of course the wattage will also be reduced to 5% of nameplate - before losses. The greedy eyes may see a 1.3kw motor making 65W as such a waste. For now I see a free 65W generator but I will try to get more, as I am greedy too.

Options of course include gearing, but there are also some wiring options that may move the voltage point to a lower RPM. Anyways I would like to limit the gearing to 3:1 ratio or lower. For now anything over 100W output will be considered a baseline for success until I go larger.

Below is a picture of an older model 850W and a newer model 450W. major difference is the newer models are half the size for the same ratings, as the 850 is almost 4 times as large as the newer 450. Stator is open on the 850.



The newer stators are sealed. But I found the star connections on the older stator, and the three coils of each phase are paralleled at the star and the Amphenol connector. The plastic-epoxy whatever of the newer stators cannot be cut, melted, or burned. But if you heat it up it becomes more brittle, and you can chip away to uncover the star junction. The 450W is also 9 coils (3 parallel coil sets) star connection. The rotor on the 450W has two rows of 9 mags each with a very small offset to overlap the magnet gap. I did not remove the rotor on the 850 since I wanted to get the wires out and recenter the shaft quickly. The 450 in the pic is scrapped for the front bearing flange. I used it on the tower in my video of the sav (attached below).

The rotation unloaded is a smooth load, no evident cogging. Tie the leads, locked rotor. Pretty stout motors. The front bearing on these motors is oversized and made for large radial loads. No real concern about heat or loading, they are made for high torque in a maintained locked rotor condition, and the outside is a large heat sink.

My initial test rig is below. The video shows the tower with the 1.3kw motor mounted to a sav. The location is NOT ideal and is NOT the permanent home, I just wanted to see it spin and take some pictures before continuing work. Permanent home has complete hilltop clearance and constant wind.
Plans include adding lift wings beyond the outer radius and extending above and below the center sav to pick up the RPM, hoping the sav will limit the maximum but still allow the wings to push in a bit more speed at higher winds.

http://www.youtube.com/watch?v=NHoNAk0PMao


I'm wanting to know what anyone else has done with servo motors, and consider my options, they do include shaft-coupling of two identical motors, different wiring configurations, and maybe some scheme of switching from series to parallel coils, star-delta, or even individual phase outputs. Just want to get the most of what I have. I have a lot of scrap electronics for caps and diodes, and a handful of low-watt switching relays.

I can dream later of putting the scrap 3kW motor on a HAWT blade, but low and slow it is for now.

[birdhouse]

lakeside-
looks like you have found some good motors to work as pma-s!  i'm pretty sure you can get more than 5% of the sticker rating out of those.  one member here has gotten more than sticker rated power out of a servo he used for a mill! 

a caution:  don't remove the mag rotors from the servos.  there's a chance they will lose their magnatism.  i've never tried, but have heard of other having issue with this. 

a second caution:  VAWTS can and do work, but they're an uphill battle.  we see many new members that love VAWTS and spend much time, energy, and money to build one that either produces nothing, or produces tiny amounts of usable power.  if you're after real power, scap the VAWT and put your energy into a HAWT.   it will be easier, take less time and produce much more power more regularly.   the 1.3 Kw motor would be a great non-geared start for a HAWT!!!!!  what are the amp ratings on it? 

there's a member here jerry that now goes by salem wind.  he has done tons with wiring configurations to gain voltage or amps, or hit a target rpm.  star will give higher volts and lower amps than delta.  there's also IRP individually rectified phases AKA jerry rigged.  and there seem to be a few ways to do this as well.  research this board, and there is more than can be digested in a week. 

i used a servo motor for my 8.5' HAWT.  the nameplate is 140v, 2000 rpm and 20 amps.  i've seen over 600 watts out of the thing in high winds.  it sits on a 70' tower to get into decently clean airflow.  you can read about my mill here if you like  http://fieldlines.com/board/index.php/topic,145609.0.html

anyways, you've got a great start!

adam

[lakesidepark]

first caution - yes and the one in the picture iwith the stator laying loose is scrapped. Although I may test this theory, I might think it would affect the positioning accuracy when on a monitored circuit for its intended use, but when used only as a generator, I don't know.

The second caution - yes I know these things, but for now there's no chance for a prop sticking above our suburban house, and our relocation is delayed. May be issues there too for a while. I've got no wild expectations and right now while I remain in VAWT land I'm in it for the hobby part of flying things in the wind. I'm not ready to cut the electric line and be griz adams. The original idea was a tiny amount of power for some security lighting, or keeping occasional trickle charge on 12V cells, and to have a platform to play with for more ideas on larger turbines. All while keeping 'low and slow' and something that won't go into runaway while I am not there.

The amp ratings on the motors as follows (all 200VAC 3-phase 1500RPM)
450W (new style) = 3.8A continuous / 2.84 N-m inertia
850W (old style) = 6.2A / 5.39 N-m
850W (new style) = 7.1A / 5.39 N-m
1300W (new style) = 10.7A continuous / 8.35 N-m inertia (Newton-meters)

I'll have to check out the mill I know its easier to figure out how to use higher voltage than it is to gear up to make speed out of torque. Just can't scare the neighbors yet.

[Bub73]

Welcome to the forum Lakesidepark;

 I figure mine like this; 1500rpm÷200volts=7.5 rpm per volt  ×15volt = 112.5rpm for useful cut in.
Figure the name plate amp rating x3 or per phase; I have a 9 amp servo the puts out over 25amps in good wind. This is just how I start to select a servo, the true data comes once they are flying as servo's vary greatly from one to the other.

Bob