3 phase transformer connections

[bob golding]

hi all,

i have a windy boy 3000 that i am trying to repair. i dont have any grid power, so i thought i might try and get the voltage of my turbine up to that needed by the inverter. around 250 -300 volts dc. i want to connect 3 single phase transformers to the output of my turbine, but am not sure of the best connection method. i found this site which seems to explain the options very well.

 http://www.allaboutcircuits.com/vol_2/chpt_10/6.html

the output from the turbine is 3 phase star without the neutral so delta delta looks the only option. i will rectify the output and put some smoothing caps down the line from the rectifier. what will 3 transformers do to the loading of the the blades if anything. i dont want to risk putting a big inductive load across my working inverter which is why i want to do it this way. also i want to try a overvoltage circuit to limit the voltage to the windy boy. think that is what killed it in the first place. i know this is a long winded way to do it but  feel it might produce some interesting results. i will use the output from the windy boy to drive a battery charger, and keep the system i am using at the moment seperate. any problems i havent thought about? i have loads of transformers and caps  and diodes so shouldnt cost me anything apart from time. i also want to use the data logging option on the windy boy if possable.

cheers

bob golding

[cardamon]

Bob,

I was/am looking at doing a similar thing, that is use a transformer with a wind turbine, but I want to go from high voltage to low voltage.  It seems rather convoluted to try to step up the turbine output to run an inverter to run a battery charger, can you elaborate on why you dont just charge the battery directly from the turbine? I dont think you can use the windy boy without the grid - it needs to sense a "grid" to work.  I have heard some propose using a sunny island to create a "grid" so that the windy boy will work, but this is an expensive proposition.  Also transformers are tricky with wind turbines because of the low frequencies which make them saturate too soon and can cause cut in problems.  There are a few good threads on this topic, if you do a search for "transformer" under controls.  I have a 240 v nominal turbine that i want to step down to 12v.  I spent a bunch of time researching and pricing tranfomers, taking into account the derating so that they would work on the lower frequency, and now I think i will just buy the transfomer from the turbine manufacturer for $1000.  HAve  fun.

[Flux]

Any of the 3 phase connections will work. Star with no neutral will be good enough although it may not be as balanced as with a neutral.

Your big problem is frequency and you need to have transformers rated for the voltage and frequency at start up. You may need a nominal 50Hz voltage rating about 3 times your start up input voltage for a typical alternator.  Even then you may need to start without the transformers and switch them in when the blades are out of stall if you want to get away in low winds. Star/Star transformer connection will start easier than any combination with a delta in it.

Flux

[bob golding]

hi,

i only need to test it. i dont intend to use it if cant access the data logging section. if it needs a grid in order to work i will test it at a friends house where he has grid power. thanks for pointing this out. i have a 16 pole alternator so dont think frequency will be too much of a problem.

cheers

bob golding

[RP]

Could you use a small sine wave invertor as a simulated grid?

[Seedler]

Hi,

I think I have what your talking about.  I have a grid tied windyboy 3000 connected to a turbine I got from china.  The inverter is rated at 300v but the turbine was only 240,  this meant the turbine had a hard time connecting to the grid.

The guy I bought it from sent me plans for a 3 phase transformer to up the voltage from 240v nominal to just over 300v nominal.  It was easy to get a local manufacturer to make the transformer.





There are a few problems though.  If the turbine drops below about 40rpm it will not startup unless it gets a massive gust.  The transformer acts like a brake.  But over 40rpm all works fine.  At the moment I have a changeover switch to change from direct feed to transformer just to get it started.  I hope to make some kind of circuit that will do this automatically.

Dee.