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A question about coil winding - Page 5

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Posted by Michael B on December 6, 2009, 10:31 am
 




You appear to understand the question. Thank you for
your response.
Multiple windings are needed for the flux density, but
this is high voltage, low current, allowing minimal wire
size, but the risk is with punchthrough. I'm considering
varnish and fishpaper. But i need to know that the multiple
windings combined at the beginning and end will yield
the effect of the total number of windings placed, without
being diminished by the shunting at the ends.

Posted by m II on December 6, 2009, 9:55 pm
 


Michael B wrote:



I haven't given this much thought, so please take these 'insights' with
a grain of salt.

In common usage, I've only seen a need for paralleled windings in low
voltage permanent magnet powered windmill alternators and dual voltage
motors, where they series/parallel them to suit low/high line voltage.

There is relatively little power produced in a windmill, so any waste
from resistance is to be avoided. The paralleled wires reduce the
voltage drop by a ratio equal to the number of paralleled conductors.
It's actually the square of the current reduction in percent.

Here is the problem. When you double up on a wire, you will be halving
the length. Your amperage capacity will double, but the generated
voltage measured at the ends of the winding will be halved. Put another
way, only half the generated current is being carried in each of a
paralleled pair. the I^2 losses are now 1/4 of what they were. Same
rules for a motor.

Each wrap of wire in a coil adds to the voltage being produced. Think of
the instantaneous voltages at one point of the winding 'leg' as series
batteries. 100 wraps = 100 tiny batteries in series.

If you parallel the windings, you now have two runs of half length.  The
physical space won't let you put more copper into the form regardless
of how you parallel them.

Now, you have the equivalent of two sets of 50 tiny batteries in series
being paralleled with each other. The voltage is halved, but there is
now more copper carrying whatever current there is.

A motor behaves in the same manner.

Is there some way of wiring this thing in a three phase 'Wye' or 'Star'
pattern? That alone will reduce the voltage across each phase winding by
 a factor of root 3, (1.7 something). That's almost the same as doubling
the insulation value of the coating.

Another thing to keep in mind is the 'ampere turns' value. That
determines how much magnetism will be produced. The amount of extra
current you can push through parallel wires will probably be offset by
the reduced length. A good motor design is probably pushing way over
eighty percent efficiency. A good transformer is probably running 95+
efficiency. That is more from good magnetic design, not winding magic.

Another thought: Is it possible to spray Glyptal of Conformal on the top
of each winding layer as the coils are being wound?

A thing with higher voltage transformers also comes to mind. The
input/output connections on the tanks (X1, H1 etc) are placed so that
the LEAST amount of potential difference is created between them.

Out of curiosity, what voltages would you be looking at? Really high
voltages have the benefit of reducing line current at a given power
transfer rate. That reduces I^2 R looses on transmission lines.

I don't know what benefits you are looking for in a very high voltage
motor. They may not be enough to offset the problems.

As for the terminations of these parallel windings, I'd *guess* a wire
with an ampacity of around twenty percent more than the sum of the
individual wires would be more than good.

Please provide a bit more information regarding horsepower, voltage and
amperage ratings. My curiosity is piqued. If this is a 'secret' project
I will understand.




mike



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Posted by Jim Wilkins on December 6, 2009, 10:22 pm
 


The Ed Grey motor:
http://keelynet.com/evgray/evgray.htm
Notice the 3500V capacitors and spark plug wire leads.

In addition to ampere turns you can consider turns per volt to
estimate the size and practicality of a design. More explanation here:
http://mysite.du.edu/~jcalvert/tech/transfor.htm
He gives 10, I've seen 1 in an arc welder.

jsw

Posted by Michael B on December 7, 2009, 3:38 am
 

Your comments about the winding was well atriculated,
thank you. I'm in the process of making a winding jig. And
probably using #30 wire.

The Ed Gray motor had multiple coils in rotor and stator,
and used high voltage, low current. And the electromagnetic
flux density apparently got very high very quickly, with a
capacitive discharge format.

Now the problem I see with the design is that the best push
is lost, because when stator coil is lined up with rotor coil,
the repulsion is the product of one against the other, or timed
so that they have missed each other. The Ed Gray motor had
its coil laminations machined so that there was a 16 degree
angle to help with the push getting good direction.

I think the kick of one such coil working against another is
a good notion, but I would rather see more direct push for
the jolt. So I am seeking to wind a couple of coils onto
transformer bodies, after taking them apart, stripping them
of their windings, winding a new coil on a form and slipping
it back on to the transformer body after varnishing each
lamination to return it to being able to reduce eddy currents.

How to use the mutual repulsion kick? Something like a
paddlewheel, or with more than two electromagnets, more
like the individual cylinders firing in an ICE.  If it can be
quick enough, a momentary contact would be enough for
the "rotor" coil to kick before it disconnects. And the
transformer body, formed in epoxy, could move like the
piston in an ICE, turning a crank.

Plenty of issues, like source, and bearings, and guides,
and a bunch more, but the first thing is to see what kind
of real world power is available. Starting small, with a
small transformer, avoiding the temptation of going with
something big like a microwave transformer body.

And the juice should be easy to come by with a voltage
multiplier, with 1N4007's only costing about 10 cents
each in quantity. But right now I have a microwave
transformer, and the diodes they use in the ovens
arranged as a full wave bridge.

There are plans for the Gray "Fuelless Motor", with
a commentary about the Gray claim about it not
depleting the batteries, but the design includes a
generator. All I'm wanting is to see if the Gray
Motor could be used as an electric vehicle motor,
with speed control being simple input voltage
control, and see if there are advantages for homebuilt
motors.




Posted by m II on December 7, 2009, 5:45 am
 

Michael B wrote:


(snipped)


Your experiment is probably the best way to find things out. Even if it
fails, there will be something to be learned.

Please post the results, either way.




mike

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