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Forum Index : Electronics : F&P cable 3 phase
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PureEmotion Newbie  Joined: 13/02/2010 Location: AustraliaPosts: 3 |
Hi all, need help with the main cable from F&P VAWT to controller (aprox 15 meters) will household cable do the job or do I need 3 cables of the same capacity? Running 3phase over the 15 meters... Trevor |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Welcome aboard Trevor, Quite a few use a heavy extention cord for the drop down the mill tower so i see no reason why 2.5mm electrical flex wont do the 15 meter run for the AC side of the mill. It would be best if all 3 phase wires are the same size. If in time you find you have a voltage drop over the length of cable or the cable runs hot than you will need to increase the cable size. But on an average a F&P dont put out that much to cause these problems and i cant see a vawt putting out max from a F&P anyway. I take it your rectifier is at the controller end and you are running the 3 mill phases to it. Pete. Sometimes it just works |
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| PureEmotion Newbie Joined: 13/02/2010 Location: AustraliaPosts: 3 |
Thanks Pete, Yes I am planing on keeping 3 phase all the way, this should keep down the Amp losses through DC cable, and the controller is designed for 3 phase. Just starting on the project, We have the post in and have a rewired F&P, looking at Lenz2 wings, we also run a 1.2KW solar tracker. Trevor |
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KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
Ahh Trev welcome aboard. Transmitting F&P three phase is not like 240V AC due to the high frequency the F&P puts out. AC vs DC no different as voltage is the same. Do some searching and you'll find it. DC is a winner. Whats the system voltage? What type of stator -please tell me a 60S for VAWT. What controller do you intend running? Can you put it at the mill end? Have you considered a cap/ voltage doubler? Still need to have it in the air -mast of sorts? 15A extension cord would be fine (3.5mm conductors) but losses even at this short distance are steep if you are running 12V. EG here volt drop calculator wire size AWG to mm2 EG at just 20Amps or 240W you have a 30% DROP. This is not acceptable for a VAWT as you are looking for everything. Go to a wrecker / crap yard and get the biggest cable you can find it will cost $6/KG -cheap and will always be worth that in scrap! 16mm2 is the minimum I would use. Herbnz has done some work on placement of recs and as close to the mill as possible is the go by a long way Luck favours the well prepared |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
BTW I use 2 x 15Amp cables down the tower BUT they are at 48V so theoretically should never even see 15A. I run 80m out to the mill in 16mm2 at 60V peak power thus call it 20A over that length call it 8% loss. As a guide should never be over 5% loss but hey how often is it going to be making 1200W? $250 in cable still put a dent in the budget! Luck favours the well prepared |
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| PureEmotion Newbie Joined: 13/02/2010 Location: AustraliaPosts: 3 |
Thanks for that, looks like I need to rethink plans a little, at this time I don’t have a controller and I thought the 3 phase would have kept the Amp lower. The cable I was planing on using was the heavy household wiring (I think 20-25 Amp)The post is a tilt over 'Red Light Camera' post it gives me 4.5 mtrs before I put a further .5 mtr post on top, the turbine will be on top of that, then the Lenz2 blades. We live in the city of Townsville and although they are wind friendly, they object to high ugly things in front yards. There is a fair bit of space inside the post for a AC/DC converter and a stop (shorting) switch so I will start looking at the better alternatives. Need all the help I can get, but in usable and small amounts.. <SMILE> Have been in contact with Randysworkshop.com and he has sent a diagram of a new mount he has designed for VAWT complete with disc brake. looks good. Thanks guys, look forward to your assistance Trevor |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Dont know if i am fully convinced Karl with a dc run being better. One thing about a 3 phase run is your power is split over 3 cables rather than 2 so lighter cables are possiable as cable is x3. Secondly i would rather have all my controlls tucked away in a shed with good air flow and better accessability. It also allows for better mill control and power dumping if needed. Think back to the discussions on your mill and the limitations that was everdent with having the dc run to the controller. There is plus and minus on either way and think its a matter of what suits your intended setup best, rather than one hard and fast rule. Enviroment damage over time out at the mill would likely cause more losses than the cable run to start with. I am not a fan of trying to squash everything into a tight box that is a problem to make changes to. Much rather a wall of the shed to mount every thing on in one place and easy to work on and add to if needed. But thats just my thoughts. Pete. Sometimes it just works |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
*** Transmitting F&P three phase is not like 240V AC due to the high frequency the F&P puts out. AC vs DC no different as voltage is the same. Do some searching and you'll find it. DC is a winner. *** First statement - correct. Do not understand the last comment. Back to a posting I made back in Sept 2009 http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?T ID=1975&KW=transmission+line where I asked for some real circuit values so that I could determine what the issue was with using LONG 3 phase cables (ie 100 metres or so), instead of rectifying at the turbine. Sounds like it is due to attenuation of the higher order harmonics. I understand that as you move from a harmonic rich AC to a pure sine wave you are going to lose power. I have access to some quite high-powered circuit simulators waiting to see what the trade-offs really are. Seems to me the most controlled environment is 3phase cable (3 phase wires plus a ground). I could measure between each conductor and ground and between the individual phases. Then add a 3 phase square wave source and see what the effects are on harmonic content. Or does someone already have this information? |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
I found it in that thread from Herbnz I think he's been stuffing about with F&P's since before I was born so I took this as gospel I myself would not run three phase AC the high frequencies due to the fundemental and the harmonics caused by the step fronted pulses charging the batteries only at the peak cause big loses in the reactance values of the cable not long ago I ran a test with a cable here and responded to a thread here but can not find it now. I always have rectifiers as close to windings as possible. Here is a consideration for you. Dump controller works out at the mill end off the three phase 2nd set of rectifiers. run the caps / voltage doubler out at the mill end too, then run to the batts with heavy cable and some smaller cable (non load carrying) to measure batt volts out at the mill. If i knew then what I know after the fact -even though I did it on the best advise at the time! if perhaps I ran a set of the three phase in normal house wiring from the mill as well as the DC, as it would only work for the dump load, losses would be good and not bad. problem again is being a dual, I would have needed two sets of three phases to avoid them setting things on fire and fighting each other. thus that idea is looser too. all of a sudden spending hundreds on cable for no gain. General consensus here (these days) is to run the cap/ voltage doubler as close to the mill as possible which I did, the problem is having battery controller at the mill end of my cable run would overead batt voltage under decent load and thus would have required lots of hands on to avoid overcharging. There is no easy way to skin this cat could be done this way too In there I would run the batteries, bat controller, dump controller, caps rectifiers AND the PVE 1200 and run 240V AC from the mill. problem with this is cable must be 600mm+ deep, in orange conduit and would involve walking out to the mill for everything, at least the majority of stuff i need access to is at the house. as you pointed out is a good idea. Unfortunately there is always a potential better way, my way I loose 20W at full load through the diode separating the mill from the batts, they are only there to smooth output for the inverter anyway, its not like I'm relying on them to run the house, just to do their job smoothing. Luck favours the well prepared |
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