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Delta, star, Jerry riged?
Jerry:
As promised I'm prersenting my thoughts on the above. I tried to find a computer program for drawing schimatics.
A freind gave me Electronics work bench but the computer and I are not freinds so I quite trying to use that program. It would be a few years before I figured it out so I've hand drawn some schimatics and then took pictures of those with my digital camera.
Sorry guys thats the best I can do for now. Please bere with me?
My insperation for posting the story was a result of my diary on my 8" dual rotor.
The debate was reborn and I thought I should spend some time explaining my thoughts.
The first thing I did this morning was to confirm my suspisions. The test subject was a GM car alternator refited with NEO magnets (Hornet). Some time ago I had seperated all 3 phases in this alt. There are 6 wires comming out of the alternator.
I chuked it up in the lathe and did a no load AC voltage test of each phase. Phase 1,2 and 3 are completely seperated from each other and have no common conection.
At 500 rpm each phase was producing 14.59 volts ac. I tested 2 phases wired in sires
This is 2/3 of star. Now a voltage reading of 25.11 v is showing on the meter.
This is going to be a long diary therefor I'll brake it up into several postings.
Befor I brake for the next post here are a few pix of the alt and the meter readings.
The next post will have more discusion and the schimatic photos.
JK TAS Jerry
Jerry:
As seen in the last photo the star reading is 25.11 volts. Now normaly you would think that two 14.59 volt coils wired in sires would produce 29.18 volts. They would if we were talking singel phase but these coils are not totaly in phase. As fack each coil/phase has a 120 degree relationship with its neighboring coil/phase. Neither one is at peak voltage when its neighbor is.
Heres a couple pix to help visulize this.
If the coils were in phase we would see 29.18 volts.
Here is a normal star conection.
The circle here is around one fullwave bridge rectifier. This is why 2 bridges are used. Reality is 1.5 bridges for normal star or delta.
Now on to the next post. I hope the brakes don't confuse things.
JK TAS Jerry
Jerry:
Although the are 3 phase it is imposable for the voltage of all 3 phases to be at there peak potential at the same time.
Dan B has stated he like the fact that all coils have current flowing through at all times. This is true.
An example of this is phase 1 is at zero potential at some point in its output do to rotor rotation. At this same point in time phase 2 and 3 are at 120 degrees either aproaching there peak output or leaving there peak output. This means voltage has to pass through phase 1 and at that instant phase 1 is just a coil in the way for current to pass on its way to the doides its connected to.
As a mater of fact the only way any of the ac voltage can reach a fullwave bridge is
to pass its current through a coil that is partialy an inductor only, or has current that is slightly in opsistion.
Puting littel inductors in sires with each phase is not a benifit. For those how understand phaseing try this wire your speaker out of phase in your audio system to see what happens to the acoutic energy.
If we could stop the alt intantly a measure what was happening at that instant we could acctuly see a DC voltage. At one end of a coil a positive voltage would be present and at the end of that coil there would be the negative. This alternates with the alternating magnetic flux but lets do that freez frame thing and check the relationship between phases at that nano second.
We would see that while one phase is producing it peak volktage the phase next to it would be produceing less. They can't all be on top of the hill at the same time. They are a manditory 120 degrees apart.
Its like wireing two 12 volt batteries in sires. Every time you tried to connect the 2 batteries one would instantly drop to 10 volts. You could never get the to be 12 volts at the same time. So you get 22 volts not 24 volts.
My proposal is to make each phase have 2 times the voltage as one phase. This solves the lost voltage isue. Then provide each phase with its own fullwave bridge rectifier. This keeps the voltage high (no phase to phase lose) The perelelling of the lower amperage higher voltage will provide the same amperage as the lower voltage higher amperage phases wire in sires.
A single phase example. A power transnformer will help to understand this aspect.
Lets say I have 2 transformers. They both have 120 primaries.
One has 2 sendaries at 10 volts 5 amps. If I wire these secondaries in perelell I get 10 volts 10 amps.
The other transformer has 2 secondaries at 5 volts 10 amps. If I wire these secondairies in sires I get 10 volts at 10 amps. This example is equal to star with one big exception I can never get 5 volts at the same time from the 3 phases or coil groups.
By wireing a seperate bridge to each phase a phase will never have to send its power through another phase that is not in total agreement.
Time for a couple more pix. Proposed coil change ans stock coil preformance.
Time to brake.
JK TAS Jerry
Jerry:
Just read the above post. Sorry about all the miss spelling and left out letters. I think its a speacial CODE. I've seen others hear on the board use it but I think you regulars can desifer it.
Hiker asked if it was still 3 phase with a fullwave bridge per coil. Actully a my fellings and thoughts about this is not nessesaraly a bridge per coil. A bridge per phase is fine. I did it because I had enough small bridges and as Dan B I think pointed out there are slight and small diferances between coils.
If 1 coil is making 10 volts and 1 is making 9.7 volts and 1 is making 10.2 volts why make the suffer like this. The high volt coils are held back and draged down by the low volt coils. Let the all participate freely without hastel.
With this home brew stuff it would be rear to see all coils at the presice same voltage.
However I don't think the diferance is enough to warrent a manditory bridge for each coil. I just did it cause I could.
A couple more pix.
The last pix is the diode bridge per phase.
Now time for more discusion.
OK guys pick me apart.
JK TAS Jerry
sahlein:
In my dim mind it seems that what you have done is to make three single-phase circuits in the space formerly occupied by a three phase machine.
The only "Phasing" remaining is just from the fact that the magnets and coils are spaced such that the outputs of each "leg" of your machine are at varying values relative to each other at any given instant.
Joe S.
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