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Forum Index : Electronics : Cct for pulsing F&P motor

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brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 10:50pm 10 Mar 2006
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You know,I'm really interested in putting together a Cct. for just pulsing this motor . I reckon if someone out there could post a simple Cct. ,I 'll put it together and try it out.
I'm so frustrated watching the blades quiver in a moderate wind ,but just  being held back by the large diameter cogging .
Anybody want to take up the challenge ?

I'd prefer that the pulse(or whatever) is given from down at the control box -I have the 3 phase ac leads coming down ,not at the top.

Bruce

Bushboy
 
RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495
Posted: 10:34am 11 Mar 2006
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  brucedownunder2 said  You know,I'm really interested in putting together a Cct. for just pulsing this motor . I reckon if someone out there could post a simple Cct. ,I 'll put it together and try it out.
I'm so frustrated watching the blades quiver in a moderate wind ,but just  being held back by the large diameter cogging .
Anybody want to take up the challenge ?

I'd prefer that the pulse(or whatever) is given from down at the control box -I have the 3 phase ac leads coming down ,not at the top.


Bruce, please excuse the horrid sketch... if you have access to a two-pole momentary-contact pushbutton (or a spring-return toggle switch, or if you wanted to get really creative - a spring-return, centre-off switch - you could "step" it by hitting phase 'a' then 'b').. this baby is a simplified diagram of what I think should work. Beware, there's no current limiting, so just a quick pulse only!



As you can see... closing BOTH poles of the switch at once, will in effect, put your entire battery across one of the coils. You shouldn't blow up any diodes, because the other diode in each 'vertical' string is still reverse-biased.

If you want another (horrible) sketch showing connection of the changeover/centre-off switch, just holler.

RossW
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 02:35pm 11 Mar 2006
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  Thanks Ross, I thought it would be a lot more complicated than that.
I'll put this together on a test stator/rotor on my bench and see what happens.  I've been told if I turn one F&P set-up ,having it directly connected to another similar ly wired unit beside it ,then maybe the turned one will turn the other (will try this also),
So frustrating seeing the mill sit there for 3 days now ,even with some breeze-I'd rather see the bloody thing turning ,evrn if it's not producing any power !!.

Bruce

Bushboy
 
RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495
Posted: 08:33pm 11 Mar 2006
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  brucedownunder2 said    Thanks Ross, I thought it would be a lot more complicated than that.


I'm a great believer in NOT making things any more complicated than they need to be.

  Quote  I'll put this together on a test stator/rotor on my bench and see what happens.


Some feedback would be appreciated. My "gut feeling" is that we really need two phases pulsed in sequence but someone else said just a kick is probably all it needs.

  Quote   I've been told if I turn one F&P set-up ,having it directly connected to another similar ly wired unit beside it ,then maybe the turned one will turn the other (will try this also),


Yes, that should work - the only thing I can see causing it not to work would be if the low speed required to get it started wouldn't be producing enough (useful) output to drive the one up the mast, but give it a go.

If you have a "spare" motor to play with, and some old low-resistance current limiting devices (can you say "old car headlights"?), you could make a safety device by putting one in series with either of the switches to limit the current to a safe value.

  Quote  So frustrating seeing the mill sit there for 3 days now ,even with some breeze-I'd rather see the bloody thing turning ,evrn if it's not producing any power !!.


Absobloodylutely!


 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 10:52pm 11 Mar 2006
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  Hey, I had a thought ,now that could be a problem,  anyhow , what about if it needs pulses,then have a current sensing coil around the phase line (ac) and a 555 timer . Now inject a pulse ,the sensor picks it up as "on" ,the timer then turns it"off" . then the cycle repeats if the motor dosen't keep revolving -as if it does it's job ,then the current sensor will not allow the timer to kick in again til it comes to a stop.
whaddathink.

ps - we found Dad, so today we are going to plant him. my sis died and didn't tell anyone where she hid him.
hahahaha.
havaniceday

bruce

Bushboy
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 01:19am 12 Mar 2006
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  Tried that --no luck , it moves the blades a very small distance -maybe a pole on the stator(like we think should happen) , but thats about it . and the more u do it the less it becomes-maybe gets saturated  ?.

Tried the "motoring one with another " no movement at all-. So, until I refine something then the wind will have to do it's job !!

  Anyhow , that's about it .

Bruce

Bushboy
 
RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495
Posted: 01:52am 12 Mar 2006
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  brucedownunder2 said   
  Tried that --no luck , it moves the blades a very small distance -maybe a pole on the stator(like we think should happen) , but thats about it . and the more u do it the less it becomes-maybe gets saturated  ?. </QUOTE]

That's entirely what I expected. I think it's not saturating, but rather as the magnets move, they get closer and closer to the coil you're energising - thus, they can't move much closer!

  Quote  Tried the "motoring one with another " no movement at all-.


Feared that might be the case, just not enough "power" at low rpms, and if you spin it quicky, the prop wont be able to get started because the field will be moving too quickly for it.

Here are two more dodgy circuits for you then:
The first should create a "moving" field from one pole to the next.




This second one will pull then push, so once your magnets are aligned with the magnetic field (as you found on the first one), flipping the switch to the OTHER side will create a replusive force now, and should push the magnets away from the coil.




 It's still not going to create a rotating magnetic field though, this was only ever a simple "bump" circuit.

If you have a small VFD (variable-frequency drive), often found on machines with (proper) speed controls on AC motors, you could unplug the machine from your charger and into the VFD and give it a tickle that way. It would produce the rotating magnetic field you need, both positive and negative cycles with the proper phase relationship.

What I've drawn above is very rude, crude and unattractive. As I said, it was just something to give a bit of a "bump". If the mill requires more than that, we may have to get significantly more complex to synthesise something closer to the mark.

Oh, the 555 idea would probably work, but if a single pole isn't enough to get your mill away by hand, there's no point even trying the 555 to limit pulse width or current.

RossW
 
brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 09:27am 12 Mar 2006
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  Thanks Ross- I'll try that tomorrow- just a breeze here at present , so nothing to get excited about .mill is swinging to point in the right direction , butquivers a bit ,trying to overcome the cogging effect-thanks for your help.
bruce

Bushboy
 
RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495
Posted: 10:05am 12 Mar 2006
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  Quote    Thanks Ross- I'll try that tomorrow- just a breeze here at present , so nothing to get excited about .mill is swinging to point in the right direction , butquivers a bit ,trying to overcome the cogging effect-thanks for your help.


I probably shouldn't tell you about the day here then?!

About 0900 I climbed the mast since it was dead calm. I took some surplus supermagnets up with me - some 3g ones and some 80g ones.

Managed to get the "light" blade pretty much on track with 9g added at the tip (these little magnets shouldn't throw off, they're N45 and stick like the proverbial sh!t to a blanket). Then by gently running the mill a little at a time, was able to work out where the remaining heavy point was, and since the opposite side was in between blades, I couldn't add it out at the end, so used the 80g magnet right in on the hub. Got the prop almost perfectly (static) balanced. Within 10 minutes of this, the breeze had sprung up enough to get the mill spinning so I thought I better get down - but upside, I couldn't feel any vibration while I was up the mast even.

A couple of hours later and I was watching a good north-westerly putting 13 amps at 50V into my batteries. (650 watts - that's nearly 50 amps into a 12V system). Anemometer shows it was only 30-35 kmh wind too. The mast still has a slight shake but nothing like the moster rattle it had before!

I'm a happy dude right now, and hope it blows all night, because the guys failed to deliver more propane on friday and I'm nearly out!

RossW
 
Chris

Senior Member

Joined: 12/09/2005
Location: Australia
Posts: 146
Posted: 12:50pm 19 Mar 2006
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I dont think its worth taking power from the battery to jump start your wind gens.

You should create a slave windmill setup, something small like the nicd windmill charger setup. Use this to jump start your windmill. This way you dont have to worry about draining your main battery, and you can pulse it more often. The smaller slave windmill will turn easier in lighter winds too. So it should maintain its charge pretty well.

I guess it depends on your setup, how often you pulse the generator. etc

Was just a idea i had rattling around in my head.
 
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