Series Capacitors and the Wintura 500

Discussion in 'General Questions' started by TomT, Nov 16, 2010.

  1. timber

    timber WindyNation Engineer

    This proposed use of capacitors in conjunction with wind turbines is a very interesting and captivating subject.
    I'm glad to see some experimentation going on by those who know what they are doing.
    Please keep us informed on how it all goes and especially where gains are made, no matter how significant.

    I'll watch from the sidelines if you don't mind, I know just about enough to be quite dangerous. :shock:
    I've always be intrigued with using caps as storage, as in flashlights etc and in theory or studies on larger scales.
    Makes me wonder if new types of capacitors will one day be developed as in recent and future developments in battery technology.

    Keep up the good work and thanks for sharing what you find out TomT, Dank and others!

    Dave
     
  2. dank

    dank WindyNation Engineer

    I have the Capacitors and have them wired up. There seems to be a wind moratorium around here. So lots of waiting. It defiantily makes a change in the signal from the PMA. But the testing is going to take more time than I thought. I should give you some of my back ground. I was in electronic repair all my life, now retired. Have lots of Electronics experience, no wind experience. Have got a lot out of the Forums so far, maybe I can pay some back. Have some good equipment left over. Best is a Sencore scope. Besides the visual part it has a digital read out on DC volts, Peak to peak and frequency. The scope trace is very different with the three caps. in series, in circuit. Higher peaks and less DC on the pulse. No extra noise or over revving. Don't have my AMP meter in circuit yet. But can't tell more without more testing. Hopefully in the next few days. Get back to you then. Dank
     
  3. timber

    timber WindyNation Engineer

    Of course the wind quit ... happens every time you put up a new turbine, change blades, make other system changes ... just a reminder that Mother Nature is in charge ... :lol:

    timber
     
  4. dank

    dank WindyNation Engineer

    Hi,
    Well Ive tried everything I could think of in the way of caps. Run caps. and electrolytic. There where changes in the blade speed but none that improved the current to the batteries. It seems most of the time it was more of a trade off. More speed and less current. I can do better testing when the wind is better. This has been a low wind year in my area. Iv'e just ordered a new set of blades. The five blade set for lower wind. Soon as I get the blades on, raise the tower and cut out some trees. I should be in a better position for testing. I even tried some electrolytic in the DC side. No luck. Iv'e sure enjoying the Forum.
    Dank
     
  5. NEOH

    NEOH WindyNation Engineer

    windyguru,
    Any positive results from your testing?
    Did the power for low rpms improve?
     
  6. leamywind1

    leamywind1 WindyNation Engineer

    Has any one come to a conclusion on using caps for a wind turbine weather grid tied or battery?
    I am interested in trying as I have a few big AC ones at 500v. Not sure how to use them with the China GTI's, if i should, or if it is worth it?

    My thoughts are as of now I have (4) 1000MF at 50v ea, 2 in series, both goups of 2 in parallel hooked on the DC side of my one rectifier with the cap flow from pos to neg as they are polartity sensitive. From there to a GTI. My thought was to prolong the watt disipation from gusts as well as keep the blades spinning longer. Not sure if my caps are to small to do this or if it even posible to do. Hell the GTI may already be doing this. It seems like the voltage drops a little slower when the wind slows down when I have the caps hooked up. This would also allow to get to a faster RPM right away........I think. Again, I am not sure if that is a sign that it may work or not?

    Any thoughts?
     
  7. NEOH

    NEOH WindyNation Engineer

    Dank,
    I do not think the circuit that TomT is experimenting with has anything to do with Motor Start Cap or Motor Run Cap circuits. Also you state, "The run cap is in parallel with the coil"- This is not true, actually the Motor Start Cap is in Series with the Start Winding. When the motor spins up, then either: 1) the Start Cap is completely disconnected from the Start Winding and then only the Run Winding continues to spin the armature or 2) a smaller Run Cap is switched in so both the Start Winding and the Run Winding continue to spin the armature with more torque than scenario #1.

    Also, TomT is using (and must use) 7,500mf Series Capacitors that are 300 times larger than the 23mf capacitors that you specified. There is a good reason for TomT to use such large series capacitors.

    Also, you state, "Usually when you hook to Elec. caps. back to back you cancel each one out". This statement is not true. Two equal "Back-To-Back" polarized capacitors do, in fact, create an equivelant Unpolarized Capacitor at half the capacitance.
     
  8. NEOH

    NEOH WindyNation Engineer

    TomT,

    I found this information that may explain the failure of the capacitors ...

    "... Do not use aluminum electrolytic capacitors in a circuit that requires rapid and very frequent charge / discharge. In this type of circuit, it is necessary to use a specially designed capacitor with extended life characteristics ..."

    Your circuit fully charges and fully discharges the capacitors many times per second when the wind turbine is turning fast. That is a no-no. Electrolytics caps are designed to have an almost constant DC voltage with a slight AC ripple. Your circuit is all AC Ripple - ouch! Your circuit will work but the series capacitors will last, at most, one year.

    Also I found this ...

    Here’s an example. Suppose you wanted the ripple-current rating for a 4700 μF, 450 V capacitor in a 3 inch (76 mm) diameter and 5 5/8 inches (143 mm) long can and the maximum ESR at 25 °C and 120 Hz is 30 milliohm. The can area – not including the terminal end – is 60.1 in2 (388 cm2). The thermal conductance is (0.006)(60.1) = 0.36 W/°C. For a 10 °C temperature rise the case may dissipate 3.6 W. So the maximum permitted ripple current with an ESR of 30 milliohm is only 11 Amps !!!

    Your Wind Turbine can create more that 11 amps, correct ?

    What appears to be happening is this ...

    At low frequencies (turbine start-up speed) the Capacitive Reactance of the Series Capacitors is very high which "unloads" the Wind Turbine and allows the blades to spin faster than when direct connected to the bridge rectifier. Capactive Reactance is the AC equivelant to DC Resistance without the associated power loss that resistors have. As the speed of the blades increases, the Capacitive Reactance DECREASES! This is a good thing, as it puts more and more of a load on the Wind Turbine as the Wind Turbine generates more power as it turns faster and faster. This makes the Series Capacitors to appear to behave like an MPPT. But, as the Capacitive Reactance decreases it soon hits a characteristic called ESR - Equivelant Series Resistance. It appears the ESR value of your Series Capacitors is too high. This is the reason why you have Run-Away. If the ESR was a very low value then at high RPMs (high frequency) the capacitors should essentially disappear from your circuit. But in your circuit the capacitors do not go to a low enough value at the higher RPM and therefore you get run-away.

    You need to purchase capacitors of the correct "type" than can withstand continuous AC ripple currrent.

    Bottom of Page #3 has ...
    1,500uf, 600Volt, 78 Amp Ripple, 2.2 milliohm ESR, Polyfilm Cap ...
    http://www.illinoiscapacitor.com/pdf/seriesDocuments/MDCL series.pdf
    
    Solution #1)
    You need to purchase capacitors with very low ESR.
    Also maybe even purchase higher mf capacitors or add another set of caps in parallel with equal values - this will cut the ESR in half and cut the Capacitive Reactance in half, both will increase the load on Wind Turbine at higher speeds. If this still is not enough load at high RPMs then also implement Solution #2 or Solution #3, too.

    Solution #2)
    Add three Normally Open relay contacts, each with a very low value resistor, in parallel with each capacitor. Then at a specific voltage or RPM energize the relay. This low value resistor will essentially "eliminate" the Series Capacitors. With the Series Capacitors eliminated the Wind Turbine will be properly loaded at the higher RPMs to prevent run-away.

    Solution #3)
    Use three Normally Open contacts from a relay to switch in another Bridge Rectifer connected to the battery to "normally" load the Wind Turbine at a High RPM setpoint.

    You may need to implement ...
    Solution #1 and Solution #2 combined or
    Solution #1 and Solution #3 combined
    
    Your circuit is working well at low and medium RPMs but the Series Capacitors have too much ESR, Equivalent Series Resistance, at high RPMs to properly load the Wind Turbine to prevent Run-Away.

    OK ?
     
    TomT likes this.
  9. TomT

    TomT WindyNation Engineer

    Looks like good info. But gave up on the idea after going to GTI's. Being that the pipe goes into the attic and the high rpms kept me and my renter up all night.
    I quit using them. I am not willing to put more into the turbines at this point to check it out. As they are such poor performers at this location.
     
  10. NEOH

    NEOH WindyNation Engineer

    TomT,
    My yearly average wind speed is very low at only 9.7 mph.
    I have only 4 months with avg winds above 11 mph ...
    Dec = 11.1 mph
    Jan = 11.4 mph
    Feb = 11.1 mph
    Mar = 11.3 mph

    The WindTura 750 is rated at 800 Watts at 29 mph.
    At 11 mph I am lucky if I would see 100 watts being generated.
    My average wind speed for Jul & Aug is only 7 mph - not enough to even spin the blades.
    
    I simply do not have enough wind to justify spending $1,000 on a Small Scale Wind Turbine.

    Also, A Wind Turbine needs to be 20' higher than nearby objects - add more costs for pole.
     
    leamywind1 likes this.

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