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4 Phase Connections
By ghurd, Section Wind Posted on Fri Sep 9th, 2005 at 06:41:43 PM MST
Options?

I might have room for 4 phases in a PMA like Ed's 'Alt from Scratch', but 8 magnets, 8 coils per phase.
Looks like Ed maybe had room too.
The recent talk about 2 phases, combined with most PMAs being an odd number like 3 or 5 has me quite confused about something with 4 phases.
Must a 4 phase PMA be rectified separately?
Is there the option for Star or Delta?
Single rotor, lams, 12V, 3A is the goal. 3/4x 3/4x 5/16" N42, #22 wire 0.425" air gap mags to lams.
G-

4 Phase Connections | 8 comments (8 topical, 0 editorial)

Re: 4 Phase Connections (3.00 / 0) (#1)
by JW on Fri Sep 9th, 2005 at 03:51:44 PM MST
(User Info)

Hi Ghurd,

Just making a wild guess here.
I think the advantage of prime numbers for stator coils is related to pie R squared. I would consider phase canceling with even numbers of coils not magnets. Could be wrong just a thought.

Re: 4 Phase Connections (3.00 / 0) (#2)
by RP (russp located-at fidnet (dot) com) on Fri Sep 9th, 2005 at 04:08:57 PM MST
(User Info)

4 Phase will be equivalent to two phase. Phase #3 will be the same as Phase #1 just backwards in polarity. The sale with Phases #2 and #4. You'll need an odd number above two the avoid this. Think about a 3Phase machine with 6 coils (two coils/phase). It won't be 6Phase.

[ Parent ]

Re: 4 Phase Connections (3.00 / 0) (#3)
by ghurd on Sat Sep 10th, 2005 at 07:18:34 AM MST
(User Info)

It's an overlapping coil design.

It looks like there will be room for 2 and a half or 3 phases under the magnets,
and 1 or 1 and a half phases between the magnets.

I can't get my head around if the 4th phase is added, will it be limited to being rectified seperatly, meaning there must be more turns, so maybe it won't fit.

[ Parent ]

Re: 4 Phase Connections (3.00 / 0) (#4)
by JW on Sat Sep 10th, 2005 at 08:33:35 AM MST
(User Info)

Perhaps you could wire the stator as a 4 leg star connection to keep all your winding phases consistant. Then you'd only need a rectifier buss with 8 diodes.

JW

[ Parent ]

Re: 4 Phase Connections (3.00 / 0) (#5)
by benjamindees (fieldBLAHlines@deesconsulting.com (remove BLAH)) on Sat Sep 10th, 2005 at 02:56:50 PM MST
(User Info) http://www.deesconsulting.com

I know what you're saying. You want to know whether you need four diodes per phase or if you can get away with two. Ed seems to use two but that seems to be dependent on having a correct layout (ie no cancellation).

I had a nice long reply written, but really I can't say for sure. It would help to have more info on your setup, either a diagram or some measurements (mag spacing, diameter, coil size, thickness, etc).

Re: 4 Phase Connections (3.00 / 0) (#6)
by Flux on Sun Sep 11th, 2005 at 02:14:16 AM MST
(User Info)

Why do you want to use 4 phase for a single rotor machine. If you have space left you could have made your 3 phase coils wider.

There may conceivably be a case for 2 phase if you try to put an overlapped coil winding in a dual rotor where there is really no room for the end connections.

With a single rotor winding you can bend the ends down over the core out of the way.Whatever you do with 2 phase it comes out the same as if you rectify separately although it seems as though you can common 2 leads and use a 3 phase bridge with similar results. If you ignore the (star) point as you would in a 3 phase winding your rectifier sees single phase. I suspect you could ignore the star point in 4 phase and the rectifier would see it as 2 phase rectified separately with twice the number of turns.

There is no true equivalent to star and certainly not for delta. For single rotor I would keep to 3 phase.
Flux

[ Parent ]

Re: 4 Phase Connections (3.00 / 0) (#7)
by ghurd on Sun Sep 11th, 2005 at 12:02:06 PM MST
(User Info)

OK. 3 Phase it is then.

Remembered something possibly relevant this morning.
With a 4 coil stepper motor wired star as a PMA,
either pair of 2 in phase coils had a much higher output than any 3, or all 4 coils, at the same RPM.

Thanks,
G-

[ Parent ]

Re: 4 Phase Connections (3.00 / 0) (#8)
by benjamindees (fieldBLAHlines@deesconsulting.com (remove BLAH)) on Sun Sep 11th, 2005 at 05:25:31 PM MST
(User Info) http://www.deesconsulting.com

With a single rotor winding you can bend the ends down over the core out of the way.

And you can do the same with dual rotors, with up to three phases. Look at Ed's diagram. You bend one layer one way and the other layer the other way. You get a stator that's the same thickness, with 3 times the amount of copper.

[ Parent ]

4 Phase Connections | 8 comments (8 topical, 0 editorial)

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