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Star confiuration
By Gblaze43, Section Newbies Posted on Mon Mar 3rd, 2008 at 11:19:30 PM MST
Question about star configuration

Hello, I'm a new member, long time reader of fieldlines.com. I have a question that needs clarification. I'm new at making electric generators, I've heard a lot said about "star configurations" in coil designs. What exactly is a star configuration, I've seen more info about Delta and wye configurations but not in regards to generators. Are they the same? also whats the benefit of that configuration?
Thanks in advanced!
Greg

Star confiuration | 25 comments (25 topical, 0 editorial)

Re: Star confiuration (3.00 / 0) (#1)
by spinningmagnets (velmis1450bc(at)aol(dot)com) on Mon Mar 3rd, 2008 at 06:33:55 PM MST
(User Info)

"Star" is the same as "Wye"

When the two leads from each coil are drawn on a schematic, if one lead from each coil is connected in the center, the drawing looks like its forming a "Y" if there are 3 coils. If there are 5 coils, it looks like a 5-pointed star.

Re: Star confiuration (3.00 / 0) (#2)
by Flux on Tue Mar 4th, 2008 at 01:13:34 AM MST
(User Info)

Just one of those language problems between different nations.

I always assumed from books that in N America Star was called " wye" ( can't imagine why it couldn't be "Y") and delta is called mesh.

Surprisingly here the terms star and delta seem almost universal. Saves me learning a new language.

Flux

[ Parent ]

Re: Star confiuration (3.00 / 0) (#3)
by Capt Slog (Capt.Slog(at this)gmail.com) on Tue Mar 4th, 2008 at 08:15:38 AM MST
(User Info)

You also asked about the benefits.

This might help...

http://www.windstuffnow.com/main/3_phase_basics.htm

.
"Slowly changing the world, one watt at a time!"

Re: Star confiuration (3.00 / 0) (#4)
by SparWeb (sparweb at ANTISPAM_hotmail_com) on Tue Mar 4th, 2008 at 09:49:47 AM MST
(User Info)

Welcome aboard!

This might help, too:

The generator will have roughly the same EMF (electromotive force) on each of the segments shown in the diagram. Eg, the EMF in 1-4 is the same, but out of phase with, the EMF in 3-6. The segments shown are actually groups of wire wound through particular areas of the stator. Different connections will allow you to add the EMF's for either higher or lower voltage, lower or higher current.

You have the highest voltage and lowest current from the series-star connection in the upper left. You have the opposite; lowest voltage and highest current from the parallel delta connection in the lower right.

I said before that the EMF is "roughly" the same in each segment. If there are slight differences in the phase groups, then the imbalance can cause a problem in the Delta configurations, but not the Star configurations.

Each of the various connections also represents a different range of operating speed. You must bear this in mind if the prop on the windmill is not to run too slow or too fast. Either can be bad when most props have a speed range where the work the best.

Steven Fahey

Re: Star confiuration (3.00 / 0) (#5)
by dinges on Tue Mar 4th, 2008 at 10:43:23 AM MST
(User Info)

I've uploaded a few pages of a motor booklet to my gallery. Not to confuse someone new but just to show that there are -many- more ways of wiring up motors than just basic star and delta.

http://www.anotherpower.com/gallery/dinges?page=24

Whilst I was scanning them in I wondered... Could the variable-torque be a possible solution for motorconversions ? Perhaps the constant-hp method, where at low speed there is high torque and at high speed low torque ?

Peter.

Re: Star confiuration (3.00 / 0) (#6)
by dinges on Tue Mar 4th, 2008 at 10:46:02 AM MST
(User Info)

My mistake.

Just -after- posting I noticed the above image applies only to two-speed motors, not the common induction induction motor.

Peter.

[ Parent ]

Re: Star confiuration (3.00 / 0) (#7)
by Flux on Tue Mar 4th, 2008 at 11:10:18 AM MST
(User Info)

In theory you can use a pole change as the basic problem is a machine that wants to run at constant speed connected to a power source that wants to raise its rotational speed with wind speed.

Large commercial machines often used two motors with different pole numbers. The snag is that pole change motors are something of a compromise and are costly. The changeover switches puts a star/delta change into the shade and people here don't even seem capable of contemplating even that.

Flux

[ Parent ]

Re: Star confiuration (3.00 / 0) (#8)
by dinges on Tue Mar 4th, 2008 at 11:52:54 AM MST
(User Info)

"puts a star/delta change into the shade"

You mean w.r.t. performance or complication of building/switchover?

Peter.

[ Parent ]

Re: Star confiuration (3.00 / 0) (#9)
by Flux on Tue Mar 4th, 2008 at 12:04:06 PM MST
(User Info)

Switch complication.

Flux

[ Parent ]

Re: Star confiuration (3.00 / 0) (#11)
by mbeland on Tue Mar 4th, 2008 at 01:10:08 PM MST
(User Info)

Please tell me why would this be so complicated?

Could the mill be by default in the best position for low wind output. Then above a given amperage, relays could be activated to switch configuration for as long as you get enough output?

Martin
Eau, soleil, le vent
[ Parent ]

Re: Star confiuration (3.00 / 0) (#12)
by dinges on Tue Mar 4th, 2008 at 01:26:45 PM MST
(User Info)

That's the idea, Martin.

But from Flux's reply I understand that the switch-over for dual-speed motors is complicated. I tried googling the web for suitable wiring and switching diagrams but couldn't find any.

Below is a drawing I made a few weeks ago for star/delta switchover using contactors. It needs 3, but K1 is not part of the actual star/delta switching; it's a fail-safe which always shorts output unless positively energized. As you can see, just for simple star/delta switching it takes 3 contactors (well, ok, just two for the actual star/delta).

The generator will also need a tacho-sensor (not shown in this partial schematic) and some electronics to actually energize the contactors. Not rocket science but more complicated than just hardwiring for either star or delta.

Also, it would mean running 6 wires down the tower. Or one would have to install the contactors and rectifiers at the top, but then it would still need a few wires to control the contactors. When using sliprings it would take 6...

Peter.

(K1 & K2 are normally closed (NC) contactors, K3 is normally open (NO)

[ Parent ]

Re: Star confiuration (3.00 / 0) (#13)
by joestue on Tue Mar 4th, 2008 at 03:13:48 PM MST
(User Info)

Why is it not acceptable to install the diodes and the relays at the top of the tower.

Why can't you epoxy or conformal coat the entire box and achieve reliable operation.
It seems the money saved in 4 lengths of wires should make up for the extra effort.

[ Parent ]

Re: Star confiuration (3.00 / 0) (#14)
by dinges on Tue Mar 4th, 2008 at 03:30:30 PM MST
(User Info)

I never stated it was unacceptable.

Just that it would still need several control lines (to control the contactors) running down the tower, along with the DC + and - lines.

For ease of maintenance and repair I'd like to have the contactors and rectifiers on ground level though.

Peter.

[ Parent ]

Re: Star confiuration (3.00 / 0) (#15)
by oztules (oztules__at__bigpond.com) on Tue Mar 4th, 2008 at 03:45:52 PM MST
(User Info) http://www.anotherpower.com/gallery/Oztules-toys

Dinges,
For AC induction motors, the speed change is usually done by changing from normal pole config, to consequent pole config, thus doubling the number of apparent poles, and halving the revs.

The rotor is in this case happy to go along with the pole change... in fact a three phase and single phase 4pole, 2pole rotor is the same animal and depending on what forces are operating on it, decides the pole no (bit hazy about this ).

Your conversion rotor is static in its pole spacing and coverage area, so I'm not sure how this would work if at all.

Should work for an induction motor acting as a genny, (with exciter caps) but???? for a conversion.

.........oztules
Flinders Island Australia
[ Parent ]

Re: Star confiuration (3.00 / 0) (#18)
by Flux on Wed Mar 5th, 2008 at 12:47:37 AM MST
(User Info)

At the risk of continuing the hijack and Tom's anger. I have to admit that I didn't think this through when I suggested you may be able to adopt a pole change.

Oz is correct, this can only work on a cage rotor, it just doesn't work with permanent magnet rotors. Anyway it was a bit tongue in cheek as the complexity is beyond anything reasonable.

Flux

[ Parent ]

Re: Star confiuration (3.00 / 0) (#22)
by mbeland on Wed Mar 5th, 2008 at 03:15:12 PM MST
(User Info)

Thanks Peter for the schematics,

I understand you would have to run 6 wires instead of 3 if the rectifiers are down the tower or instead of 2 if they are up but couldn't these wires be smaller since each of them takes less current?

Also, instead of having a tacho sensor with wires up and down the tower, couldn't it be simply some device to measure the output from the mill (I guess in current would be best) and trigger the contactors above a given current value?

Thanks for helping me understand,

Martin
eau, soleil, le vent
Eau, soleil, le vent
[ Parent ]

Re: Star confiuration (3.00 / 0) (#23)
by dinges on Wed Mar 5th, 2008 at 04:12:35 PM MST
(User Info)

Martin,

Assuming that in all three cases the same amount of power would be lost in the wiring:

In the case of 3 lines (AC) coming down the tower vs. 2 (DC) coming the tower: yes, with 3 wires (more or less in parallel) you could use thinner wires and still end up with the same line loss. The new wires could be 20% or 25% less in diameter. I'm not sure which of the two figures is correct, still pondering that myself and won't get into detail here, as I'm already accused of thread hijacking. The difference is mainly academic anyway.

In the case of 6 lines (with star/delta at ground level) vs. 3 lines coming down the tower, since the wires are now in series (2 sets of 3 wires), each of the 6 wires would actually have to be thicker than the wires in the 3-line-AC system. Since total length of the wires is now doubled, area of each wire should be double too (or in other words, diameter should be (sqrt(2)) = 1.41 as large.

At least, if I understand things correctly. If not I'll be no doubt corrected by others :)

Peter.

[ Parent ]

Re: Star confiuration (3.00 / 0) (#24)
by dinges on Wed Mar 5th, 2008 at 04:27:34 PM MST
(User Info)

Better explanation:

http://www.windstuffnow.com/main/3_phase_basics.htm

Peter.

[ Parent ]

Re: Star confiuration (3.00 / 0) (#21)
by finnsawyer on Wed Mar 5th, 2008 at 08:49:07 AM MST
(User Info)

It would be possible to place a regular three phase (a 12 magnet 9 coil) and my single phase design (12 magnets 18 coils) on the same rotor/stator set up. The three phase would be inboard of the single phase, both having the same size magnets and coils, although the set for my design should be wired two in hand. If I am right about the power relationships the three phase could be used for low winds with a switch over to the single phase at an appropriate point. Both alternators would be providing power at the high end. Mixing three phase and single phase outputs should not be a problem when charging batteries.
GeoM
[ Parent ]

Re: Star confiuration (3.00 / 0) (#16)
by kurt on Tue Mar 4th, 2008 at 03:46:00 PM MST
(User Info)

kinda a thread hijack on a simple question there Dinges we tend to discourage that in the newbies section.

http://www.reresource.org/

IRC
[ Parent ]

Re: Star confiuration (3.00 / 0) (#10)
by Gblaze43 on Tue Mar 4th, 2008 at 12:43:14 PM MST
(User Info)

Thanks guys! A lot of good stuff to look at.
I would like to die in my sleep like Grandpa, not screaming in terror like his passengers.

Re: Star confiuration (3.00 / 0) (#17)
by spinningmagnets (velmis1450bc(at)aol(dot)com) on Tue Mar 4th, 2008 at 05:41:14 PM MST
(User Info)

Just for trivia laughs, "Delta" is the phonetic pronunciation of the Greek letter "D", and its symbol is a triangle. When drawing a delta configuration of three coils, it forms the shape of a triangle (as seen above).

[ Parent ]

Re: Star confiuration (3.00 / 0) (#19)
by Gblaze43 on Wed Mar 5th, 2008 at 08:06:52 AM MST
(User Info)

Following the Y or star configuration, does anyone know a good template or method to follow when winding coils in star confiuration? or point me to it would be appreciated!

thanks again, in advanced!

Greg

I would like to die in my sleep like Grandpa, not screaming in terror like his passengers.

Re: Star confiuration (3.00 / 0) (#20)
by ghurd on Wed Mar 5th, 2008 at 08:17:45 AM MST
(User Info)

Dan CAD stators,
http://www.fieldlines.com/story/2003/9/11/84741/6758
G-

[ Parent ]

Re: Star confiuration (3.00 / 0) (#25)
by tecker on Thu Mar 6th, 2008 at 04:39:08 AM MST
(User Info)

A star connection can be any cluster in either low or high voltage terms . Yhe Y connection denots a 120 phase shift in with star connection.

Star confiuration | 25 comments (25 topical, 0 editorial)

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