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DaveP68

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Joined: 25/11/2014
Location: New Zealand
Posts: 292

Posted: 10:52am 04 Mar 2017

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Just built a 'Capacitor Tripler' and got 510 W output @ 300 RPM using a 36 pole copper stator wired 6x 2c Delta with a Black rotor cap.

This can be used on a 48 V battery system as it puts out 59 VDC at 8.65 A, so better performance at 300 RPM and could be used with say 3 M blades.

Using a Dual set up with a different stator for a cut in of around 80 to 90 RPM it should be possible to extract about 1 kW at say 350 to 400 RPM.

It does require more torque to drive at this lower RPM so unsure how efficient the power transfer is, as that hasn't been checked yet.

The capacitor values have to be chosen carefully, as the capacitive reactance has to be matched correctly to the stators impedance to get best results. Also it does have a peak operating range from 200 to 400 RPM, above that power extraction levels off but does still increase at a reduced rate of > 1.2 to 1.

The impedance of a stator drops significantly when it's rewired from star to Delta and even lower with different stator cuts i.e. 2x 6c, 3x 4c, 4x 3c or 6x 2c. I have formula to do the calculations to get the correct capacitor values for both a 'Capacitor Doubler or Tripler'.

Tried this 'Capacitor Tripler' on a 100s 42 pole stator, but only got 310 W at 300 RPM. With a Phase 1 rotor cap I got 360 W at 300 RPM, but they have more cogging at low RPM.

DavidEdited by DaveP68 2017-03-06

There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :)

gpalterpower

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Joined: 19/07/2009
Location: Australia
Posts: 175

Posted: 08:07pm 04 Mar 2017

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Hi Dave,
You are really putting some serious effort into F and P motors to increase the output, and at such a low rpm. Excellent results

Would that work as well on a 24v system? Im still trying to get hold of another stator and black rotor setup...so far no luck. Probably a dime a dozen in NZ

Marcus

if it aint broke dont fix it!!

DaveP68

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Joined: 25/11/2014
Location: New Zealand
Posts: 292

Posted: 09:48am 05 Mar 2017

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Hi Marcus

Yes have been putting a bit of time into getting more power out of these F&P stators at lower RPM levels.

The 'Capacitor Doubler or Tripler' can only be used practically on a 48 VDC battery systems, not 24 V as the impedance of the stators just gets far to low. The capacitor values increase by another 4 times when going from say a 6x 2c to a 12x 1c stator cut.

If you want to make use of the capacitor multiplier on a 24 VDC system the capacitors become very expensive as they need to be well over a 1000 uF and that is the AC value.

David

There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :)

gpalterpower

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Joined: 19/07/2009
Location: Australia
Posts: 175

Posted: 10:19pm 05 Mar 2017

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Thanks Dave, I had a look on line for those caps.. they are expensive and rather large in size too! They would need to fit within my mill and there just aint the room. I can see that my next inverter project will be of the 48v configuration. Everything just seems to work easier at that level.

Marcus

if it aint broke dont fix it!!

KennyG
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Joined: 06/03/2017
Location: United States
Posts: 12

Posted: 01:35pm 14 Mar 2017

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Hi Dave , I've been working on an F&P myself and have been going by a post that Gordon left . He was saying with a 24v system starting out with 110uf ac rated caps. Is this not correct ? Thanks

KennyG

DaveP68

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Joined: 25/11/2014
Location: New Zealand
Posts: 292

Posted: 11:30pm 14 Mar 2017

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Hi Kenny

I do use the same circuit that was illustrated by Gordon, but use it in a different mode of operation. The through rectifier passes no current when the capacitor values are chosen correctly for maximum output i.e. 1.4 W per RPM for the doubler and 1.7 W per RPM for Tripler.

** Please note the Tripler requires far more torque to turn, translating to loss of efficiency which was only tested for proof of concept.

The mode of operation is derived by calculating the impedance of the stator which varies depending on Star vs Delta then which cut is used, 1x 12c, 2x 6c, 3x 4c, 3x 4c or 6x 2c (I only use 36 pole copper stators for my set up not the older 42 pole version).

Once the impedance is know then the capacitor value is derived from a formula of Xc=1/(2xPIxFxC) but needs to be rearranged to derive the value of C.

Wc=capacitor reactance in ohms
PI=as you will know 3.141592654
F=frequency of the stator output i.e. 24Hz per 60 RPM so 500 RPM is 200 Hz
C=Capacitor value in Farads, so 110uf is 0.00011 which will make the impedance way too high even at 200Hz (500 RPM).

If you are interested in giving me a hint at your set up, can calculate what the capacitor values for say a doubler?

Do you have a 36 pole copper stator with a Black rotor cap?

I don't bother using 42 pole stators as their output is 40% less for the same RPM.

Cheers

David

There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :)

KennyG
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Joined: 06/03/2017
Location: United States
Posts: 12

Posted: 02:50am 16 Mar 2017

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Thanks David , Do you have any diagram on the circuit that you are using . I like to explore all my options before I actually try this . I have a 24v system . You seem pretty knowledgeable . I got another stator that has aluminum poles. I'm going to rewind it with 1.0 mil wire but am not sure how many turns I should do . Any input

KennyG

KennyG
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Joined: 06/03/2017
Location: United States
Posts: 12

Posted: 02:53am 16 Mar 2017

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Also , it's a 36 pole , white rotor cap. Could not find a black .
Thanks again

KennyG

KennyG
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Joined: 06/03/2017
Location: United States
Posts: 12

Posted: 07:29am 16 Mar 2017

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Hi David , I apologize . I was doing things while reading your post . I thought you did not use Gordons circuit . I don't need a diagram . Maybe some values though . Also , any input on how many turns when winding a 24v stator. Thanks again !

KennyG

DaveP68

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Joined: 25/11/2014
Location: New Zealand
Posts: 292

Posted: 12:33am 17 Mar 2017

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Hi Kenny

As stated above in this post..

The 'Capacitor Doubler or Tripler' can only be used practically on a 48 VDC battery systems, not 24 V as the impedance of the stators just gets far to low. The capacitor values increase by another 4 times when going from say a 6x 2c to a 12x 1c stator cut.

If you want to make use of the capacitor multiplier on a 24 VDC system the capacitors become very expensive as they need to be WELL OVER a 1000 uF and that is the AC value.

Also the capacitor doubler is best mounted as close to the stator as possible.

My setup suits a 45-90 VDC input Grid Tie Inverter for best results as that is what I've done most of my testing for. A 48 VDC system will give similar results though, but slightly less.

So my advice is to stay away from low voltage systems both 12 & 24 VDC if you want the most out of a capacitor multiplier used the way I set them up.

Cheers

David

There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :)

KennyG
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Joined: 06/03/2017
Location: United States
Posts: 12

Posted: 04:56pm 17 Mar 2017

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Hi David , I think I'm stuck with a 24v system , having 9 kw inverters. Cost of caps isn't an issue . I have quite a supply. I have a large unusual VAWT that I'm starting . If you're not sure on the number of turns on the coils that's okay .
Thanks

KennyG

DaveP68

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Joined: 25/11/2014
Location: New Zealand
Posts: 292

Posted: 08:22pm 17 Mar 2017

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Hi Kenny, the capacitors will need to be 10,000 uF 250 VDC to handle the very high through current and you need 12 of them. At about $100 each they are not cheap if you need to buy them!! Do you happen to have 12 of that exact value?

The rectifiers will need to be at least 50 ADC minimum with 6 required if you follow Gordon's circuit design.

Cheers

David

There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :)

DaveP68

Senior Member

Joined: 25/11/2014
Location: New Zealand
Posts: 292

Posted: 11:42pm 11 Apr 2017

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Hi Kenny

Got the calculation wrong on the capacitors required for that doubled on a 12x 1p Delta to be used on a 24 VDC battery system. They need to be 1650 uf AC (3300 uf DC).

That's a more reasonable working value.

Hope this update is of use to you.

David

There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :)

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