Winding "two in hand"

[TheCasualTraveler]

I didn't do very well in a search for this and it's not in the Otherpower Glossary but I have a question about winding a coil "two in hand". I assume from the posts that I have read that this is simply winding a coil with 2 strands of wire side by side instead of one. It seems that the purpose of this is the ability to change the voltage and current potential by manipulating the physical structure of the wire in the coil. Let me ask a question that will help clear it up for me. I wound a coil with 120 turns of #22 awg wire (0.64516 mm). If I was to rewind this coil with 2 strands of the same wire and 60 turns and the ends of the wire were connected would I have,

The same voltage potential?  (120 turns vs. 2 x 60 turns)

Half the resistance?

Twice the current carrying ability?

Thanks,

[RP]

Yes, in that case you'd still have 120 turns so it'd be the same.

In reality, 2 in hand or even 3 or 4 in hand winding is not usually done for multiple voltage adjustment.  It's usually done that way because really thick wire is such a bear to wind into nice tight coils.  

If I recall correctly, 2 in hand 15 gauge is the same as 12 gauge single and when you get up to 10 gauge, that's a real bugger to wind.

[TheCasualTraveler]

Thanks, but I keep seeing where one gauge wire is compared to two in hand of another gauge wire. I'm wondering about both coils using the same gauge wire. In that case doesn't the two in hand give less resistance and more current potential?

Thanks again,

[ZooT]

I don't know.......from what I've been reading here, current (considering the wire only), is determined by the diameter and corresponding volume of the wire.....and if two in hand matches a single strand of a larger gauge in volume, it should produce the same aomunt of current because the volume of the material in which electrons can be excited is the same.....and by the same token should produce the same resistance for the same reasons......

Am I correct?

 

[Flux]

The number of turns decides the voltage you get. The size of wire determines the resistance and is one factor in determining the current you get.

Normally you would choose the thickest wire that will go into the space and give the chosen number of turns. Sometimes the ideal wire size is too thick, either to handle physically or with these alternators you run the risk of eddy loss in very thick wires.

In theses cases you can make up the same cross sectional area of copper by using more than one strand of smaller wire and it behaves as if you used the thicker wire but without the problems mentioned. There is no actual gain or advantage except where I have mentioned about the limitations of very thick wire.

Sometimes it is done for other convenience reasons. If you ideally needed #12 but you had a reel of #15 then using 2 in hand #15 would do exactly the same job.

With multiple wires in hand, the turns are decided by the number of times you coil the bunch round the coil. 120 turns of a single wire would not be the same as 60 turns of 2 in hand when connected as you would normally do. It is possible to re connect the 60 turns of 2 in hand to give the same voltage as the 120 turn coil, but it requires you to connect the start of one strand to the finish of the other. It is not normally used this way, but it would be one way of winding for dual voltage ( in low voltage machines only).

Apart from the limitations of thick wire mentioned there is no virtue in using multiple strands in hand. For a given size coil wound for a given voltage you can not get lower resistance by fiddling about with multiple wires. If the size is practical then go for a single wire and have far less ends to bare and connect.

I can't help feeling that to many people this is all a lottery, you will find misleading information if you look hard enough, that is inevitable where hundreds of people post information. The main thing is to get to understand what you are doing so that you can weed out the nonsense. I hope this clarifies the issue for you.

Flux

[TheCasualTraveler]

It clarifies it a great deal Flux and RP and XooT and I feel rather stupid now looking at this simple problem. I see now that what I was talking about was simply a series and parallel circuit. The single wire coil would be series and the two in hand connected in parallel would have half the resistance, twice the current ability but the voltage would be HALF also. Otherwise it would be against the LAW. Ohms law!

Thanks all.

p.s. note to admin, can we have a fool button we use to delete embarrassing posts? J/K

[southpaw]

Andy

No fool button necessary ,reading this type of question and the answers just helps fix the basics in my mind and brings me one step closer to taking the plunge and actually building a turbine rather than absorbing my electrons from the computer screen.

Southpaw  

[finnsawyer]

Go back and do your homework again.  Each of the two shorter windings has half the resistance because they have half the length, but the same cross section.  Connecting them in parallel cuts the resistance in half again.  So, you get 1/4 the resistance.  No magic here, though.  The voltage is cut in half.  If you short out the windings the power dissipated in the coils will be the same for the two cases, being VxV/R in the first case and (V/2xV/2)/(R/4) = VxV/R.  No free power lunch.  Conservation of energy (via power) still holds.  

[Flux]

Yes you are right about the series and parallel bit.

Not quite right about the resistance. You have half the resistance with one strand of 2 in hand because it is half as long but you have 2 strands in parallel so the end result is 1/4 the resistance.

The same applies to a coil with half the turns of wire with twice the csa. You again end up with 1/4 the resistance.

This is one reason why the low voltage alternators need a very low resistance and also need extra low resistance connecting leads. At half volts you have twice current for the same power and  as the loss is proportional to current squared then this balances the 1/4 resistance and gives the same loss.

Don't feel a fool, not much of this is obvious when you meet it. You will get the hang of it with patience.

Flux

[TheCasualTraveler]

Right as rain Fin, I should have done the math with ohms law instead of just assuming like I have been. That way I would have caught the resistance going to 1/4 or at least known something didn't add up. Thanks guys for your patience.