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Single phase Coil Leg Width


By GerryS, Section Mechanical
Posted on Mon Feb 12, 2007 at 05:03:24 AM MST
Should coil legs be 1/2 magnet width or equal to magnet width?

In many of the diagrams I see for single phase machines there are half the number of coils as there are magnets (for instance those diagrams from Ed at Windstuff). In many other examples on otherpower (like those single phase designs by the Dans) there is one coil for every magnet.  Which is a better design?  What are the advantages of each?    
Single phase Coil Leg Width | 9 comments (9 topical)

Re: Single phase Coil Leg Width (3.00 / 0) (#1)
by Flux on Mon Feb 12, 2007 at 12:49:14 AM MST

There is no significant difference between the two methods in any machine with a closed magnetic circuit. If you were silly enough to try a single phase single rotor design with no return path for the flux then the version with the full number of coils would work better.

In slotted core type machines it seems to be largely a preference of the designer, America tends to favour the version with half the number of coils. Europe tends to use the same number of coils as magnets. I think it may have evolved from the method of winding adopted in the early days. Once a convention is started it tends to stick.

In air gap designs where resistance is the dominating factor on output it may be that in some cases the resistance may be marginally lower for the full number of coils but not enough to choose one method over the other.

Flux



Re: Single phase Coil Leg Width (3.00 / 0) (#2)
by electrondady1 on Mon Feb 12, 2007 at 06:13:37 AM MST

there is one other option for single phase .
you can use one coil per mag and wide legs  
if you overlap the coils .  //////
 

[ Parent ]


Re: Single phase Coil Leg Width (3.00 / 0) (#3)
by GerryS on Mon Feb 12, 2007 at 11:34:01 AM MST

These are the only designs for single phase that I can come up with.  I think the first setup is the one usually used in older single-phase Otherpower windmills (except the coil legs are narrower perhaps in the older Otherpower designs.)  The second setup seems optimal to me for peak voltage generation.  The third maybe would be just as effective as the second.  








Re: Single phase Coil Leg Width (3.00 / 0) (#4)
by Flux on Mon Feb 12, 2007 at 12:18:06 PM MST

This should show the two versions. One has twice the number of coils the other has twice the turns per coil.

As you can see the first arrangement may have a slightly longer turn length but there is little in it.



Flux

[ Parent ]



Re: Single phase Coil Leg Width (3.00 / 0) (#5)
by GerryS on Mon Feb 12, 2007 at 03:36:45 PM MST

Flux, what do you mean "There is little in it."  Little in what?

[ Parent ]


Re: Single phase Coil Leg Width (3.00 / 0) (#9)
by Flux on Tue Feb 13, 2007 at 01:14:02 AM MST

Your first diagram was odd and best avoided to avoid confusion.

Your second and third show the two ways to connect a single phase, but you show it with different scales. The issue is also confused somewhat by having round magnets and coils which implies an axial design and it is a bit remote from the normal single phase discussion to machines in general.

I showed the same thing as it would be done with a radial machine and with the same size magnets.

For a motor or a conventional iron cored alternator where resistance is no big factor the windings would be equivalent and interchangeable . The first has half the coils but each coil contains twice as many turns. The second twice as many coils each with half the turns. The turns/phase is the same in each case and the winding area is the same and the total wire csa is the same.

The only difference is that the first version will end up with a longer length of wire and will have a slightly higher resistance and for axial air gap things with no reacance the lower resistance winding will perform a little better. As Ed said the version with the same number of coils as magnets will do a bit better.

Sorry if I think in terms of normal machines, the rest of the world does as well. If you learn all your machine theory from what is done here then you will meet with strange reactions from engineers brought up on conventional machines. These ironless axial machines are odd by any normal standard and sometimes you have to think about the implications of the changes. The addition of rectifiers to any alternator puts it into the realms of special and again the implications are difficult to deduce from conventional experience.

Flux

[ Parent ]



Re: Single phase Coil Leg Width (3.00 / 0) (#6)
by willib on Mon Feb 12, 2007 at 04:58:11 PM MST

the third diagram is actually a three  phase machine , without the proper wiring ,as you have it wired.
so in my mind the second one is the only true single phase.
the magnet spacing is too wide in the first one.


Carpe Ventum (seize the wind)
[ Parent ]


Re: Single phase Coil Leg Width (3.00 / 0) (#7)
by windstuffnow on Mon Feb 12, 2007 at 07:16:09 PM MST

  The third one is a single phase machine where the coil legs are shared, its actually the best of the 3 ways shown.  All of my single phase machines are done this way, as well, some of the 3 phase machines I've built are done this way with 2 more sets of coils added for the other 2 phases.

.
Have Fun! Windstuff Ed
[ Parent ]



Re: Single phase Coil Leg Width (3.00 / 0) (#8)
by willib on Mon Feb 12, 2007 at 08:17:06 PM MST

You're right , sorry dont know WHAT i was thinking?
i'm used to looking at it laid out on the disk, not flat ..
no excuse really , sorry.


Carpe Ventum (seize the wind)
[ Parent ]


Single phase Coil Leg Width | 9 comments (9 topical)
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