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DaveP68
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Posted: 05 July 2017 at 12:32am | IP Logged Quote DaveP68

Yep will go with that about starting them young, my little boy is 4 & 1/2 and already show lots of interest in what goes on in the work shop.

Wow tower climb with the young chap. Must say from photos you've posted, that's a great view from the top.

Can I ask what part of the US you're located in?

Also what timber did you make those blades from?

Cheers

David


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kitestrings
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Posted: 05 July 2017 at 3:25pm | IP Logged Quote kitestrings

We have four boys: ages 31, 12, 9 & 7. My youngest seems to be the most determined to "help". He's really into tools, jacks, things with engines and the like. I'm usually a stickler when it comes to safety gear - this is how I found on a recent day in the yard.

We're in the northeast corner of VT; aptly named the "Northeast Kingdom". We're about 20 mi. to the Canadian border.

We used balsam fir for our blades. If I was given a choice I'd probably use Sitka spruce, but it is not local. Balsam is locally available - we cut these logs and had them locally sawn, and air-dried - it is pretty strong for its weight, but is not as resistant to rot as say cedar.
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DaveP68
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Posted: 06 July 2017 at 10:29am | IP Logged Quote DaveP68

I thought you had sourced your supply of timber locally, good on you as that is the renewable approach for sure.

We travel to the US every 2 to 3 years and have family and friends in Pittsfield, MA not that far from your state. Next visit may try to look you up to pay a visit.

That's a wee bit of an age gap between the 4 boys. We only have to one at present.
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gpalterpower
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Posted: 12 July 2017 at 7:42am | IP Logged Quote gpalterpower

Hi Dave,
I been following this thread with some interest as I have always been looking for a way to control the sometimes "Out of Control" fan on my mill. The furling works ok, but I am all in favor of having a secondary backup to slow things down when wild weather hits. It is scary to see those blades spinning at break neck speed. Is your controller purely based on sensing over voltage, or can the system be incorporated with the R.P.S to slow things down. This would suit in my case as the mill is fed with a 24vdc supply. Marcus

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DaveP68
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Posted: 13 July 2017 at 8:24am | IP Logged Quote DaveP68

Hi Marcus

Thanks for taking an interest in this topic.

This dynamic brake circuit has been modified for 24 VDC operation but requires the IGBT switching device and dump load resistor to be in parallel multiples.

The trip voltage is set for say 29 VDC (adjustable) and the load resistors can be reduced to 5 ohms. You would need a minimum of 5x IGBT switches and 5x 5 ohm dump load resistors set up in parallel. All feed from the same drive transistor to each IGBT gate input.

This again is "Concept Only" and does not reflect an actual operational circuit!



The actual voltage trigger circuit would be some logic to trip then keep the clamp circuit on for the desired braking period. This could be minutes to say a few hours to said high winds have passed. Could also have an anemometer input to release the brake once winds have dropped to an operation level after a set period.

What are your thoughts?

David
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gpalterpower
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Posted: 16 July 2017 at 2:15pm | IP Logged Quote gpalterpower

Hi Dave,

Thanks for your help in adding to your original circuit diagram even though its still in the concept stage. I'm assuming there could still be a few bugs to iron out. Are you planning on testing one soon?

I like your anemometer idea, but would it be possible to somehow utilise the f&p speed sensor to just slow the mill down and not come to a complete stop. More like squeezing on the brakes to a useable speed. This way it could still charge, but not be out of control. Maybe too complicated

Marcus

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kitestrings
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Posted: 17 July 2017 at 3:05pm | IP Logged Quote kitestrings

Quote:
We travel to the US every 2 to 3 years and have family and friends in Pittsfield, MA not that far from your state. Next visit may try to look you up to pay a visit.


Normally I'd say that's a bit of a haul form where we live, but in relative comparison (to NZ ) it is quite close. By all means look us up if you can.

Years ago I worked for a wind small manufacturer that did induction, grid-tied turbines. They employed hydraulic braking early on, and then went dynamic braking. On the larger (40-50 kW) units they used electric water heater elements in free air as the resistive load. It worked quite well, but they also used "tip brakes" on the blades which were operated by centrifugal force if the rotor exceeded its operating range. This prevented run-aways in the event that there was a gearbox failure, or malfunction of the dynamic brake. It also added another maintenance item however.

I generally favor control strategies where the fail-safe mode is just that; something fails and the system shuts down. If you can incorporate that into the braking scheme it will likely work out best in the end. ~ks
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DaveP68
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Posted: 29 July 2017 at 2:31am | IP Logged Quote DaveP68

kitestrings wrote:
[QUOTE] I generally favor control strategies where the fail-safe mode is just that; something fails and the system shuts down. If you can incorporate that into the braking scheme it will likely work out best in the end. ~ks


Yes fail-safe mode is the best approach to take. What I'm proposing here is complementary to the fail-safe system that always should be there.

It's like having reverse thrust on aircraft jet engines which of course can fail to deploy on landing. But the wheel brakes are always there no matter what happens, just need to brake harder in an emergency if reverse thrust fails due to engine failure.

This dynamic braking idea is still only at a concept stage as I don't have a wind turbine to test it on. That's why I haven't bothered trying to make a fully operational unit yet as it requires more control circuitry to function on an actual wind turbine. So there no bugs so to speak Marcuus in this concept only circuit. It does what it was designed to do.
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DaveP68
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Posted: 17 September 2017 at 5:09am | IP Logged Quote DaveP68

The main reason I've been able to get good results from 'Power Factor Correction Capacitors' is due to the constant current control that this dynamic braking circuit provides.

Can now get up to 2.7 W per RPM peak from a single stator between 500 & 600 RPM.

When the optimum current is kept close to a constant value of 2.3 Amps from a 36 pole stator wired Delta, then the voltage can rise to the level required for maximum output power.

It's an easy circuit to build if you can get hold of a scrapped F&P motor control module.

Have been able to get more than a 1 kW out of my test stator using the module in the photo on the previous page. The catch is not to run the test for more than 10 seconds as the heat in the resistor gets the module VERY HOT!
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DaveP68
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Posted: 01 January 2018 at 7:00pm | IP Logged Quote DaveP68

Haven't been on here for a while, so thought I'd update this topic relating to the use of this dynamic brake control circuit.

Modified it to be used as a fully programmable dynamometer (enhanced VFD) to measure the efficiency of F&P stators. Having lots spare motor control modules from scrapped washing machines thought I'd re-purpose one to used as a fancy VFD.

Now able to test F&P stators in different configurations or applications such as MPPT (Wind mode), how linear power curve is vs RPM constant load or as a voltage clamp to simulate battery charging.

It uses 2x F&P stators connected back to back. Stator #1 is the drive motor in it's factory stock standard star mode. The second stator can easily removed and changed for another set up in a different configuration star vs delta wired 1x 12c or 2x 6c etc.

Currently has an operating range of 23 to 250 RPM (most testing is in 92 - 250 RPM range) maximum input drive power is 470 W. Hope to modify the F&P motor controller to widen the operating range from 23 - 650 RPM with 3x the input drive capability up to 1400 W. The RPM measurement is done by the motor controller and shows on the display module. This can only be viewed in a special diagnostic mode hidden from your washing machine user.

The dynamometer function came about by adding a fully programmable board that interfaces into the reference point of the PWM circuit comparator to make it's own adjustments. This allows full control over current 0.05 to 6 Amps DC and/or voltage from 30 to 500 VDC.

Just a simple re programme to change the test mode. Won't be publishing this new circuit at this stage. Will take to much effort with most of it on bread boards and in my head not on paper.

A photo of the complete setup running at 201 W continuous output at 216 RPM (note the glowing resistor in the blue module).




Close up photo of the motor controller that makes it all happen.




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SparWeb
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Posted: 02 January 2018 at 4:49am | IP Logged Quote SparWeb

Looking good. I see you have many tricks up your sleeve, like the test mode in the F&P module.

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DaveP68
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Posted: 02 January 2018 at 5:53pm | IP Logged Quote DaveP68

Hi Steven

Yes that very useful function in the display is not in the technical manual, it requires special know how to get to.

You can't just set up a system like this and hit the start button. It requires a deep understand that only the F&P design engineers have. Have a friend who designed the very same circuit board I'm using in my test rig. It's sometimes not what you know it's who you know

Here's a photo of a board covers removed for those that and are interested.




David

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