# number of coils to a generator.

Discussion in 'General Electronics Discussion' started by robin9000, Feb 2, 2014.

1. ### robin9000

16
0
Oct 29, 2010
I am looking at designing and then building a generator for a wind
turbine and would like to figure out a few things.

Every example I have seen thus so far shows generators using 3
coils for each phase in a 3 phase generator but I would like to know
if it's possible for to use more then 3 coils for each of the 3 phases
of the generator as so I can produce more electricity such as 8 coils
for each of the three phases. I am thinking of wiring in star / series as so
not to put the amps to high for the wire and up the voltage.

I was thinking of using 24AWG wire. It seems to be rated for 3.5 Amps.
But I would like to know because I can't seem to find it anywhere, is there
a maximum amount of volts I can put through the wire. I am sure there is
but what is it? Is there a chart somewhere for max volts for wire, like
there is for Amps.

Thanks for any help in advance.

2. ### duke37

5,364
772
Jan 9, 2011
I do not think that you will be able to make an efficient alternator. You will need expensive machinery to make the metal work. You will be better to use a car alternator, perhaps modified, say with a permanent magnet rotor.

Alternators use three phases as this is the simplest to produce a continuous rectified DC output. Each phase will have a pole piece wound with many turns of wire. Use few turns for low voltage and high current or many turns for high voltage and low current.
I do not know what you mean by coils, there is only one winding on a pole piece.

The current allowed in a wire will depend on the cooling which could be quite high in a wind generator
Data that I have says 3A/sq mm or 1935A/sq inch in a transformer.
The voltage allowed will depend on the insulation. I presume that you will not be going mad on voltage. I should think that interturn voltage of 100V will be OK with good undamaged enamelled (magnet) wire.

3. ### robin9000

16
0
Oct 29, 2010

What I mean by coils is each of the windings of wire. I was thinking of high voltage / low amps. Thus if I could use 8 coils for a single phase of the star configuration I was thinking
to have each winding max out at 3 to 3.5 Amps and each winding put out as much voltage as the wind would allow for. Thus maybe 10 to 12 layers of wire and maybe a 1/4" to 1/2" thick, for each of my windings, what I was calling coils.

I'd like to hit a total output of 1KW in wind speeds of 8mph

Looking to create the hole thing in such a way as so the magnets side of the generator will be levitated as so it will start in very low winds. Maybe 2 to 3mph start up.

Forgot to add here I am making it AC, not DC. Going to the grid with it so DC is pointless.

Last edited: Feb 2, 2014
4. ### jcurrie

128
1
Feb 22, 2011
google building a ac generator, you will find anwsers there.
jc

5. ### robin9000

16
0
Oct 29, 2010
I already done that. Did not find what I was looking for. Would not ask if 8 windings per phase could be use if I could have found it somewhere else.

Have spent many days researching this stuff but no luck to figuring out if more windings per phase could be used in a AC generator.

Never mind, finally found it. For anyone else reading this yes, it's possible. I did not know but it's called
multi-pole. I did not know the correct term.

Last edited: Feb 2, 2014
6. ### duke37

5,364
772
Jan 9, 2011
If you are connecting an AC generator directly to the grid, then the generator will need to run at a certain speed. You will need a variable pitch propeller to get optimum output.

The voltage will be fixed and the current will depend on the applied torque.

Changing to DC and then back to AC gives more latitude for optimisation.

How big a propeller is needed to get 1kW?

7. ### jcurrie

128
1
Feb 22, 2011
head still spinning, on the orignal you had 3 coils of wire per phase i assume in a delta configuration if you used more coils per phase it would have to be in multables of 3 like 9 per phase with a equaly bigger magenet ring. there is a guy on line that built a 1kw gen from scratch using 14awg mag wire , not on grid though.
jc

8. ### robin9000

16
0
Oct 29, 2010

It would be a wind turbine so it would be the wind generating the power. I don't plan on changing from dc to ac, just simply create it as a AC generator to start with. As for the wiring configuration it would be wired as Star as so to generate a higher voltage rather then amperage.

One other thing I'm designing it as a VAWT so no propeller.

If there is something I am missing here in my understandings of how I plan on going about
this please let me know what I am missing.

I can provide a picture of my final drawing when done if you think this would help before I get
started on the construction of it.

Last edited: Feb 2, 2014
9. ### jcurrie

128
1
Feb 22, 2011
i woupld recomend two books for you the first is THE Wind Power Book then The Electrical Generation Handbook, as far as going on the grid just got through working for a electrical coop there rules on wind genration werer you had to have two ratchiting meters one in one out they would buy back power at 2 for 1 in other words for every 2 you put out they would give you credit for 1 , also they required some means of speed control so your output would be in sinc with there supply.and needles to say matching voltages.
jc

10. ### robin9000

16
0
Oct 29, 2010
I must be missing something, I don't see any links to what your talking about but to simplify things how can you possibly control how fast the wind turns a turbine. I mean if the wind blows it's going to generate electricity that will be used by my house or go back to the grid and if it dose not blow hard enough it would of course not produce any electricity. It would be the same thing as solar panels but the electricity there would have to be converted using a inverter from DC to AC and then sent to the grid.

That's the basics of it, is it not?

After getting lucky online I found some information explaining that generators are usually done in DC because the power needs to be rectified regardless of weather or not the generator is in AC or DC and
then passed onto the grid.

Last edited: Feb 3, 2014
11. ### jcurrie

128
1
Feb 22, 2011
there is no link its the title of two books your local libary might have them if not check online book stores, as of for the speed don't know on turbine but the blade driven ones have varible pitch blades to adjust speed, the faster the mags pass the coil the higher the cycle rate of the out put.
jc

12. ### robin9000

16
0
Oct 29, 2010
If you view the third image down on the following page you can see what I am going for in design.
http://en.wikipedia.org/wiki/Darrieus_wind_turbine
As you can see here, it's not the same. There is no adjustments like that of a regular design so it's quite literately what ever the wind gives you is what you get from it. I think my main problem was understanding that DC or AC I would still need a rectifier to make the electricity into the correct voltage and frequency for the grid, also found out they are needed because they automatically stop power flow when the power grid goes down.

Now I just need to try and understand how to Do a DC instead of AC, seems a lot harder.

13. ### duke37

5,364
772
Jan 9, 2011
]In Canada the mains frequency will be 60Hz so an alternator with just three poles, one for each phase will need to run at 3000RPM 3600RPMif connected to the mains. You can use more poles to give a lower speed but the alternator will be bigger.

I would suggest that you get the turbine running first and then consider how to utilise the power. Direct connection to the mains means a fixed turbine speed.
There is an 'interconnector' between france and england to supply power. Even though the frequency is the same, the phase will differ so the link is DC., they would not go to all the complication if it were not necessary.

Last edited: Feb 3, 2014
14. ### robin9000

16
0
Oct 29, 2010
From my understanding now I must either go with DC from the start or a AC and then use
a inverter in between to make it suitable for the grid. This allows for the power to enter the grid then whenever the wind blows at what ever speed I am able to get out of the wind turbine. I wish there was another way around it but as you stated it needs to be 120VAC
at 60Hz to be good power and thus the reason why I need a inverter.

I am now thinking maybe just convert the AC to DC and then back to AC again. AC seems to be
way easier to make. I read I need a rectifier to convert AC to DC, one of the biggest problems I am
having is finding a suitable inverter to change high voltage DC into AC power so it looks like
I need a step down inverter.

So to sum it up I think I need to do the following;
1. AC generator (high volts / low amps)
2. Use a transformer to convert the power to (low volts / high amps)
3. Use a rectifier to convert the AC to DC
4. Use a inverter to make the power output to the grid 120VAC 60Hz.

Last edited: Feb 3, 2014