Tesla Rotating Field Motor/Generators

[Farmhand]

Hello Everybody, I am starting this thread for the sharing of information,
sources of information, construction methods/tips, operating methods and
informal/formal operational data, (test results) relating to the rotating
magnetic field motor/generators built by those contributing to this thread.

I have been researching this for quite some time and I think I am at the point
where I can successfully build an experimental two phase/induction rotating
magnetic field motor/generator.

I've been using this book, The Inventions researches and writings of Nikola Tesla ,
hereafter to referred to by me in abbreviation as the IRWNT book.
As well as the relevant patents I'll list some below.

I plan to build one in the style of the one shown by Nikola at the worlds fair,
because this was one of his first experimental models.

It is shown as exhibit 'C' in the picture below Page 478 of the IRWNT book.
Exhibit 'C'



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The text from the book Page 479 to describe the device is quoted below.

Another prominent exhibit was a model illustrated at c which is a twophase
motor, as well as an induction motor and transformer. It
consists of a large outer ring of laminated iron wound with
two superimposed, separated windings which can be connected
in a variety of ways. This is one of the first models used by
Mr. Tesla as an induction motor and rotating transformer. The
armature was either a steel or wrought iron disc with a closed
coil. When the motor was operated from a two phase generator
the windings were connected in two groups, as usual. When
used as an induction motor, the current induced in one of the
windings of the ring was passed through the other winding on
the ring and so the motor operated with only two wires. When
used as a transformer the outer winding served, for instance, as
a secondary and the inner as a primary.

Chapter III (3) deals with the theory of the operation of the motors.

This is a motor Page 20 of the IRWNT book.


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Relevant Patents.

Electrical Transmission of Power Patent 382 280



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I have a suspicion one of these setups below could be used to power a
household. As shown with converter. And used to do it in different ways.

Dynamo Electric Machine-Patent 390 721


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As can be seen by the patent picture above the rotating magnetic field is
very useful, it can be used in transformers too.

I think all the information needed to build a working motor/generator or
converter to fill our needs is contained in this old book and the patents.

Regards


P.S. Anyone considering building or already building "any" Tesla rotating magnetic
field devices can feel free to join in contribute or ask questions.
But please just try to stay on topic, and with valid information sources linked,
preferably from recognized sources of Tesla's own information and theory.

Comments and constructive criticisms are ok too.

..

[Farmhand]

First steps.

OK so I have done some research and now I am ready to start to design and
build an experimental device.

I have removed this field from a 7 Kw rotating field motor from the case and
will now remove the wire so I can use the lamination's to make an annular
steel core.

I cut the housing in half to remove the field. I recommend when cutting
aluminium housing and such, to use bee's wax on the cutting disc for a smooth
cut, doing this stops the build up of aluminium on the cutting disc, when
aluminium builds up on the cutting disc it causes obvious problems.
Being careful not to cut too deep, if you see sparks you are cutting steel.
Don't cut the steel lamination's, even stopping short and breaking the last bit of
alloy with a wedge is a good idea.


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There is about 30 mm of steel to work with, which will make the full ring.


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Each lamination looks something like this picture below, i'll cut off all the
existing pole projections so I have nice smooth ring lamination's, I'll decide
how many lamination's and therefore how wide the core will be later.



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Next step for me is to remove the wire. Which might take a while.

Oh and here is a picture of the housing with the field in it, there are lots of pole projections, it was a three phase motor.



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Cheers

[Farmhand]

I made some progress with the core lamination's.

I found the easiest way to get the wire out was to cut the wire off flush with
the end lamination. Then tap the wire out with a metal rod and small hammer.



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So now I have this, the steel is very soft. Should be easy to cut. 36 poles.


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I need to work out exactly how I will deal with it before I separate it.



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I recommend if working on a round thing of this weight that rolls well, to make
extra sure it won't roll off the bench

[Farmhand]

OK I found that just a simple pair of tin snips will work to remove the little pole
projections from the lamination's, the set I have are right handed and will cut left hand curves.

I'll spruce them up a bit with a file later. I've don four and I'll need about 60 for
a 30 mm wide core. Compared to uncut one.


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Cheers

[Farmhand]

Hi all, I was thinking about the field coils I'll need, I was wondering if there was
anyone who could help with some very complicated looking calculations.

I'll be winding four coils on the field core like in this picture, the core will be 30
mm x 30 mm square cross section and 220 mm diameter, if each of the four
coils take up 100 mm of inner circumference there is a small space between
for mounting about 25 or 30 mm or something, anyway so I think 100 turns of
1 mm wire in each of the four coils will be enough. I could do layers or thinner
wire.

Any thoughts ?

I just thought I would throw that out there in case anyone wants to try their hand at the calculations.



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Cheers

[Iotayodi]

Been watching your progress on this. A definite job ahead. I was wondering how you separated the laminations. Cant help you with the calculations. Its amazing that Tesla and others like him can do them in their head.

[Farmhand]

Been watching your progress on this. A definite job ahead. I was wondering how you separated the laminations. Cant help you with the calculations. Its amazing that Tesla and others like him can do them in their head.

Hi Iotayodi, The lamination's are easy to separate from this motor, there is a
kind of reverse V recess cut into six places around each lamination and a long
staple is located and flattened in place to secure all the lamination's in place.

Like this picture, I just peel the staple back a little bit to loosen them and
carefully lever them out.



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I just calculated it will take me about ten minutes to trim the little pole pieces
off one lamination, I have 60 to do so it will take at least 10 hours work just to
do that.

Cheers

[Farmhand]

Hi all, I made some progress with my first experimental setup, I've wound the
first of four transformers on the laminated core. I'll post some pics and specs below.

The first photo I'm using one primary winding each way to get AC, however
when the other transformers are wound both 1 mm primary winding's can be
used in parallel, or in series, and each opposite transformers primary will be
connected in series with each other forming two sets of two primaries, the
secondaries can be connected in different ways for different needs.

This kind of setup should be able to be used for many purposes such as
transformer, 12-220v inverter, step down converter, phase converter,
and with an armature/rotor also a motor or generator even a rotating
transformer using the field coils as primaries and the armature coils as
secondaries.

I think before I wind the other transformers I'll work out how I will mount it so
an armature/rotor can be introduced.

Primaries-
2 x 1mm x 48 turns, 0.1ohm, parallel inductance 560 uH, series inductance 2 mH.

Secondary-
5 layers of 0.5 mm x 210 turns per layer, 1050 turns, 10.2 ohms, 212 mH.

Transformation ratio- 1:21.8 with series secondaries,
with parallel secondaries or series primary winding's (ie both primary winding's
per transformer in series) 1:10.9 ratio. THe primaries of opposite transformers
are always connected in series with each other to form two pairs at 90 degrees to each other.


This is powering a 25 watt 240 volt bulb with 280 volts @ 31 Khz


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This is the primary


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I might use it for higher voltages so I used wax paper between the layers.
When I wind it I mount it upright with blocks of wood clamped to the core
and use a mirror so I can see the back side of the coil. I'll have to make
sure not to clamp the coils though as I do the others.


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This is the core material I used .


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Cheers

[Iotayodi]

Excellent! Been wondering on your progress on it.

[Farmhand]

Hi Iotayodi,I think I've made a mistake with this one, I might have trouble
mounting it so that it can be used as a motor. I think I can still modify this one
to be secure enough by removing the wooden separators not next to the
transformer already wound and slotting the core a bit so that some 6mm
aluminium plate separators can "lock" into the core slot while clamping the core
and bolting the whole thing solid to a piece of wood, the mounting board can
have a hole in it to take the shaft and one bearing can bolt to the board,
from there its just some kind of frame I need to make.

I've got plenty more core material so I can just make more. I'll try to test
some stuff with this one. If I can mount it well enough on a solid board I can
do some stuff with it I think. If not, this one might be just a transformer.

The whole board could be turned on it's side and mounted in a frame with more
boards and more fields and rotors added, I hope.

I was surprised of the frequency it will work at, seems to handle 30 Khz ok so
far, maybe it won't fare so well with more power from four transformers on the core.
I wonder what it would take to saturate the core.

The core is 15 mm x 30 mm cross section 220 mm OD 160 mm ID, laminated.

Cheers

[Farmhand]

First observation is that at 30 Khz with a 3.4 nF cap across the secondary coil (output)
the idle power is about 2.5 watts.
With the 25 watt bulb for load the voltage at the output is 280 volts and the
input power about 38 watts, I guess the bulb must be dissipating over 30 watts
when its working from 280 volts rather than 240.

I surmised it must be because the secondary was near resonant frequency so
I reduced the frequency to 21 Khz so there is 244 volts across the load and
the input dropped to about 28 watts. So the numbers seem to check out for
the conversion ratio and efficiency. If I take the 2.5 watts idle power from
the 28 watts input, I get 25.5 watts when the 25 watt load is added,
good enough for me.

Those measurements are not accurate enough to draw many conclusions
from, though it does appear to be around 90% + efficient with this load.

Cheers

[willy96]

now were talking brother !

this is what ya should be building

great choise and wonderful job on this thred !

i have built many things such as this ..

W



here we are now !

[Farmhand]

Bit more progress, I made some brackets to slot into the core to hold it and
prevent it rotating. The brackets and bolts are stainless steel and non magnetic
pretty much. The angle brackets are aluminium. The core will rest on wooden
blocks and the brackets will lock the core and clamp it down to the blocks, it
should be fairly solid .



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Now I can wind the rest of the coils.

[Farmhand]

Hi all, More progress. I finished winding the coils.



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The secondaries have about 10.5 ohms each. Next step is to clean it up
a bit and bolt it down, then I can design and etch a heavy duty PCB for the
PWM. I've got a PWM board I can test with but it gets warm with too many amps.
I also need to cut a rotor disc from some steel.

Cheers

[Farmhand]

Bit more progress, I'm almost ready to do some testing, I made a drawing to
show how I will make the connections, at the moment I have the second set
of primaries polarity reversed compared to the drawing to do some testing and
probing. As a transformer I think it would work better wired like the drawing.



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I don't have a rotor cut yet so I might rig up some free spinning steel disc soon.
The PWM circuit can go from 20 Hz to 100 Khz with pulse width adjustable from 48% x 2 down to nothing.



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Cheers