Series wiring PMA's info?

JaybirdJaybird Registered Users Posts: 19
I bought this Missouri wind and solar brand 48v, 800 watt, 9 blade PMA really cheap (175-200 watts in 25 mph wind). It begins making a little power at 12-15 mph. Can I take another one these 3 phase PMA's and wire them in series on the dc side of the rectifier and effectively move the power band down to say 12-15 mph.

My tower is 43 ft tall in open field overlooking a wheat field.

P.S. how do you change your signature? I've came along ways since my 12v system:)

Thanks in advance. I don't post many questions cause I can find most of my answers on here.

This site Rocks. Thanks BB,Cariboo,niel, and all of you guys that teach more people than you know.:D

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Series wiring PMA's info?

    At the top right of the page, there is a "Settings", click, and then look for Edit Signature on left, 1/2 way down. Or click on this link:

    http://forum.solar-electric.com/profile.php?do=editsignature

    Regarding your wind turbine... No, you cannot put two turbines in series to boost the output voltage.

    And there is nothing electrical/electronic you can add (like a transformer or boost converter) that can increase the power output at lower wind speeds.

    Changing blades to a different profile/diameter could help at higher speeds (but with the risk of damaging the turbine in higher wind speeds)... But it is difficult to get a lot of power out of low wind speeds.

    Wind Power increases with the cube of the wind velocity... At 7-10 MPH, most turbines are just about starting to produce a few watts of power. At 20 MPH the energy in the wind is:

    20^3 / 10^3 = 8x more power from 10 mph to 20 mph

    The other way to get more power is to put the turbine on a 60-90 foot tower (or taller). At less then 60', there is usually a lot of turbulence in the air flow (buildings, trees, roughness of the ground, etc.). And turbulent air has much less power in it vs non-turbulent air.

    In the end, it is very difficult to get a lot of reliable power from a typical car alternator type design.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JaybirdJaybird Registered Users Posts: 19
    Re: Series wiring PMA's info?

    Ok, I ask because on they're website they're selling a dual stator/ dual rotor PMA and are saying to wire it in series on the dc side of the rectifier to "Charge in low winds". I can't find many articles on it and some people on youtube just show amp meters and bad wiring which I tend to ignore. Just trying to learn :)
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Series wiring PMA's info?

    Interesting--twin alternators. That does make connecting in series a bit more interesting (both rotors are always turning the same speed)...

    Probably have to wait for somebody else that has more experience in Wind than I--But there is still the issue of how much energy the turbine can collect at those lower wind speeds.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JaybirdJaybird Registered Users Posts: 19
    Re: Series wiring PMA's info?

    I'm a newbie at wind, and there is alot of different methods companies use to sell turbines. Just want to see if anyone actually tried it and had any success. I don't mind sacrificing the amps to get a decent wattage at lower wind speed.
    The turbine does fair (i guess) at high speed. We had tornadoes and thunderstorm all through the midwest the last few days. At 58 mph wind I turned out 13 amps pretty consistant at 51.2 volts.... She was singin :)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Series wiring PMA's info?

    They're relying on simplistic knowledge of electricity: 'X' Volts from turbine 'A' in series with 'Y' Volts from turbine 'B' equals 'X+Y' Volts. Works with batteries, so why not with turbines?

    Well it doesn't work with batteries either if one battery has a different current capacity than the other (as with PV). The lower power contributor to the string becomes a limiting resistance.

    Now if the two turbines are attached to the same shaft and thus spun at equal speed their output would always be identical and so connecting them in series would work. But then you have to have enough rotor to spin the increased mass in the low wind. If you add more blade surface it will work but ...

    Not quite as bad as the AC output in series (which reduces power by creating high frequency output equivalent with half trying to push its Voltage through the other half's resistance) but it is unlikely to work.

    "I don't mind sacrificing the amps to get a decent wattage at lower wind speed." No Amps = no Watts. You need both sufficient Voltage to be above battery charging set point and sufficient Amps to affect that charge.

    You can't create power out of thin air, so to speak.

    And if you do set up a turbine to be efficient in low winds, guess what happens in high winds? Right: it becomes inefficient. Your tornado force winds will likely take it to pieces no matter which turbine you get.

    This is not to say there aren't ways of making turbines more efficient, or more efficient at the typical air speeds experienced where you are, or able to adapt to varying air speeds. It's just not as simple as "take two, connect them in series".

    I'm sure ChrisOlsen would have a word or two about this.
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Series wiring PMA's info?

    From a very simple point of view--Remember that Power = Voltage * Current

    And power = RPM * Torque

    So, if you double the voltage, you will get 1/2 the amperage at the same RPM*Torque...

    As Marc said, no such thing at "Free Energy" or a free ride.

    58 MPH is a lot of wind (and my condolences to the tornado victims in Oklahoma last night). Most turbines begin to limit output around 25-35 MPH as they cannot handle that much power (remember that wind power goes up with the cube of the wind speed). Whether the limiting action is because turbine furls out of the wind, blades begin to stall, etc... What would be interesting is a graph of output current (or power) vs wind speed to find the maximum output at what speed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JaybirdJaybird Registered Users Posts: 19
    Re: Series wiring PMA's info?

    Ok thanks, what I meant was = I don't mind sacrificing the big watts at high wind to settle with a decent amount of watts at low wind.
    I fully understand all that. So taking another identical turbine with the same blades in pretty much the same environment (can never be exactly the same) won't help too much. I might experiment with it at some point unless It just won't work at all.

    Agreed BB, an actual performance chart would be nice. I will have some fairly accurate numbers as time goes forward and will try to make one.

    As the wind increased in gusts I did notice it was pretty well maxed out. Like the blades would flatten out or stall.
    I guess that's the trick. I need one that'll survive 50-80 mph winds on a regular basis but make some power at that low 13-20 mph wind. An elusive thing it seems like.
    I'll keep researching.
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Series wiring PMA's info?

    That is why there are so many DIY wind turbines mounted on 60-90+ foot tall towers.

    The turbine itself is the "cheap" and "simple" part... It is all the over design and protection that make the difference between a good and a poor turbine.

    And most of the costs are going to be in all the rest of the stuff (tower, concrete, electronics, batteries, dump loads, heavy equipment to install tower/hoist turbine into position, etc.) is going to be 3/4 of the cost of the system (or more).

    There are few people that I have seen that have a successful wind installation. Chris Olson is one of them--And he went (relatively) big plus it was a DIY (Do It Yourself). Not much in the way of reliable "home sized" reliable wind turbine out there. It takes a lot of money/effort to do wind right.

    There is no small wind on short towers that is going to do much more than look pretty turning in the wind.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JaybirdJaybird Registered Users Posts: 19
    Re: Series wiring PMA's info?

    Understandable. I have an 80 ft reinforced concrete silo about 175 ft from my house and always thought I'd build an observation tower out of it as we haven't did silage since I was a kid. Then I got a cheap turbine and thought I'd learn a little before sticking one or two up there. I've already got the equipment to put one up there so installation costs are mostly copper I'm thinking. Thanks again for everything
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Series wiring PMA's info?
    Jaybird wrote: »
    Understandable. I have an 80 ft reinforced concrete silo about 175 ft from my house and always thought I'd build an observation tower out of it as we haven't did silage since I was a kid. Then I got a cheap turbine and thought I'd learn a little before sticking one or two up there. I've already got the equipment to put one up there so installation costs are mostly copper I'm thinking. Thanks again for everything

    The 80 foot silo will get you above the general ground turbulence and slow air, but the silo itself will cause turbulence and so you will still need a substantial mast or tower to get the turbine above the top of the silo. You will not have the problem of vibration and noise indoors that you would if you tried to mount a turbine on your house, but please recognize when designing the mast that there will be considerable side force and vibration trying to take it down. Also provide some safe way to lower the turbine for maintenance. Trying to work at the top of a pole is bad enough. When the pole is at the top of an 80' silo, it is a lot worse.

    You have not said anything about your wind speeds. If your average wind speed (day and night average over the whole year) is not more than 15 MPH, it is probably not worth the effort.
    If you can put up an anemometer with a recording output at the top of the silo while learning and playing it will tell you a lot and may save you wasted effort.
    SMA SB 3000, old BP panels.
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