Hi, I understand what you are saying and the input is appreciated. The wind turbine is just one application. The faster any PMA spins the more it acts like a electric brake. The problem relates to the internal resistance of the stator. Even if you make the PMA with a low internal resistance and use very large magnets, the problem still exists. Without finding a solution to this problem it is like driving your car with the emergency brake on. Take the wind turbine out of the equation. This problem has to be solved first before anything else can be considered. I only found out about the solution seven months ago, there is still a lot of work to do on the circuit before a micro and feed back circuits can be added.

Problem that still needs to be address:

finding a circuit that will limit the input voltage to below 400 volts

any suggestion are welcome

 

The faster any PMA spins the more it acts like a electric brake

How? There is eddy current drag caused by moving a magnetic field near a conductor (or vice versa), but a PMA design should avoid this. Frictional and eddy losses should be very small compared to the "drag" caused by the load. If you're referring to the effect of the load, there's no way to design around that.

 

Hi, this video can explain the problem better then I can.



http://www.youtube.com/watch?v=0TE38SOdf64

The load will always be experienced. Using a buck converter helps reduce the stator lose.
When they add a micro to control the duty cycle they call it MPPT. This is all very new to me, but I realize the importance of the circuit and I will continue to work on it until I have a working circuit.

It looks like a crow bar circuit is the solution for the buck converter over voltage protection. I do not know anything about crow bar circuits. I have some reading to do. If any can point me in the right direction so I design a circuit that will work at the input of my buck converter, comments are welcome.

Steve has thread at http://www.vawts.net/t48980263/mppt-testing/ on MPPT. His project is working.

 

Like I told you in your first thread, you can't believe everything you see in a Youtube video. The part before he puts his circuit in place is exactly how they use an electric motor/generator in braking mode. The output from the gen is shorted together, phase to phase with a resistance(lamp). This is simple brake mode operation. good for slowing down a wind gen in high winds.

A buck or for that matter any converter will have no effect on "internal resistance of the stator". That resistance is only due to the resistance of the wire used in the stator coils, nothing more nothing less.

The faster the shaft of the gen turns will cause a larger back EMF, in effect making the gen to a certain point act like a motor. As the voltage and current increases past a point it over powers the magnets. Making them repulse the magnetic flux in the stator coils, which makes it a motor.

If you listen to what the guy says in the video,around 2:10 minutes, what he has is a SMPS on the circuit board. Powered by the PMA. NOT a buck converter. And he is taking the data from that to track the input and output of the whole PMA and board. You have to listen to what he(video) is saying, not what you think is happening. But its not my time and money being pored in to this.

What happened to your original DIY PMA? I see you switched to a converted F&P motor from the one you started with, is it because the video guy has that as his PMA?

 

Ah, got it, I didn't realize you were just talking about impedance matching. I guess I reserve the term "loss" for the more unpredictable stuff.

 

I get your point, but you overstate the case. More data is never a bad thing. Studying and mapping the PMA output response to rpm and applied load supplies TONS of useful design data, such as the emf per pulse and the inductance of various winding configurations. Waiting to collect such data until you've built an entire installation would be foolhardy.

I'm talking about gathering data for a controller. Sure driving the gen with a motor will give data on the gen, but won't tell you if your "turbine" will give enough power to drive the gen. That can only be had from real world tests of the two units together. And till you have those units on a temporary installation, you don't know how much force the tower will need to withstand. Its all a balancing act, or you can use the old saying "when in doubt, make it stout", but that usually results in a bad, jury-rigged monstrosity.

Would you try to design a DC-DC converter without knowing what the input is? This is Burnit's second thread on this, all the other guys gave up on him after one or two posts when he didn't want to hear what they were saying, but I'm stubborn and really want to help him.

 

I have verified his result with my prototype circuit.

this is a video of my prototype circuit
http://www.youtube.com/watch?v=B3dLzZZ5jKQ

The problem I am working on now is a crowbar circuit for the input of buck converter. I need to find a circuit and select the parts that will trigger the SCR at 400 volts. I do not know how to calculate the input current when the input voltage is 400 volts but I suspect it will be around 4 amps, but I am not sure. I prefer to focus on the problem I am working on, the crowbar circuit. Thanks again


I needed more then one PMA to test with, the F&P was low cost. I still have the one I made.

 

Hi, the limiting factor of the buck converter is the inductor. Then I selected all the parts to give the greatest range of operation. Finding a crowbar circuit that will trigger at 400 volts is my next problem that needs to be solved.

 

hi, loss not lose. thanks for the edit

 

http://www.jameco.com/Jameco/Products/ProdDS/387268.pdf

Hi, I was checking the data sheet for the inductor I am using and I not sure what I am looking at. There is a column for inductance value @ current. Is this the value that should be used to calculate the switching frequency for the buck converter? Comments welcome

 

Again not trying to start a fight or put you down. But I don't really think you are talking about a MPPT. Like A MPPT for a Photovaic panel a wind Mppt is supposed to prevent the PMA/gen from destroying its self. It has nothing to do with the actual battery charging although most of the do also have charge controllers built in. And a micro is not a real requirement, it all can be done with analog logic circuits. The micro also make data logging easier.

When you had your first thread going I did some research but didn't save it, went and searched again today and found this. http://www.wind-sun.com/ForumVB/showthread.php?9805-Classic-Clipper-MPPT-Wind-Turbine-Controller Read post #5. This is what a MPPT is supposed to do.

Heres another good link about MPPT- http://www.tuc.gr/fileadmin/users_data/elci/Kalaitzakis/J.33.pdf

Going back to the first video you linked to, if he had put the light bulb after a diode bridge it would have done the same thing his circuit did. Without the rest of the circuit.

If you have the time and want to humor me, you could do the same thing your self and see. Experiments to do -

1. Wire a lamp between two phases of your gen. Predicted results - the gen will be very hard to turn and won't light the bulb.

2. Wire two of the phases to your bridge rectifier and the bulb to the rectifier out put. Predicted results - The gen will be easier to turn and the bulb will light just as well (maybe even brighter) than with your circuit connected.

All you have to lose is a little time and you may prove me wrong. If I'm wrong I'll leave this thread and never bother you again. That ought to be worth something.

 

Hi, no disrespect intended but you are wrong. I did perform the experiment you have suggested. I could not illuminate the light without the aid of the buck converter. Thank you for trying to help.

 

Hi, to update the reason for this post. It is not about wind turbines, it is about finding or designing a buck converter circuit that will work with a permanent magnet alternator. All PMAs are not the same, they produce different outputs. This is making providing the design parameters very difficult.

What has been accomplished:
I was able to find the parts to fabricate a 5 amp output buck converter with a controller circuit that will allow manual selection of the duty cycle. The output of buck converter will drive a resistive load or can interface with 12 volt deep cell for charging.

I was not able to find the parts that would increase the buck converter current output above 5 amps.

I fabricated a controller that is capable of driving four of the 5 amp buck converter.
The buck converters are connected in parallel. The PMA is being used for Vin and a 12 volt deep cell is being used for the load. I am currently testing the system and will post results when available.

Searching for input over voltage protection circuit that will trigger at 400 volts to prevent damage to the buck converters.

 

http://www.wiringdiagrams21.com/2009/11/28/a-typical-crowbar-circuit-diagram



Hi, I plan to alter the circuit to include two 200 volt zener diodes in series to replace ZD1. I am not sure if the zeners will brake down at 400 volts.

I also found a link where a high voltage laser circuit using a opto-coupler to trigger the SCR when the zener diode brake down occurred.

The strategy at this time is to use a load between the output of Q1 that will act as brake for the turbine when the SCR is trigged and include a opto-coupler circuit to provide the trigger signal. Then the circuit will reset when the turbine slows down.

There maybe better solutions. I have orders some parts for experimentation.

This maybe the solution for the input over voltage protection circuit. Comments welcome

 

Hi, I do not know if the Zeners will breakdown at 400 volts. The trigger signal is from the DC side at the bucker input. L1 is from the AC side; single phase; from the PMA. If the SCR fires it will reset when L1 returns to zero. Load could be a heating element so the PMA stator would stay cool. May be a possible solution for the input over voltage protection circuit. Comments welcome

 

Hi,
concept drawing for OVP for buck converter input.