Nikola Tesla You have to watch this

The bit I can’t get my head around is in a two-phase system, surely it’s 50/50 which way it goes. In a way it’s like a three-phase motor working on one phase.
It’s to late at night to think any more on it.
 
Tony said:
The bit I can’t get my head around is in a two-phase system, surely it’s 50/50 which way it goes. In a way it’s like a three-phase motor working on one phase.It’s to late at night to think any more on it.
Click to expand...
For interest I just drew on a piece of paper two magnets with the fields reversing and rotating,do me a favour,when you work out the answer,let me know as well
icon7.png
Nicola Tesla was much more than the world has so far given him credit forHe was a giant,a genius,a man eons in front of most other famous inventors Thanks for that link Tony,it was very interesting
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Des 56 said:
For interest I just drew on a piece of paper two magnets with the fields reversing and rotating,do me a favour,when you work out the answer,let me know as well
icon7.png
Click to expand...

The only way I can think of doing it is with shading rings in each pole piece face. But that means the motor can’t be reversed.
There is mention in the film of copper rings by the poles so I think that must be it.
 
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Des 56 said:
Nicola Tesla was much more than the world has so far given him credit for. He was a giant,a genius,a man eons in front of most other famous inventors
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I agree!

I always had Faraday as the inventor of the (3 phase) induction motor.
So who actually did invent it? (can't be bothered googling)

I will build a Tesla Coil someday soon...
 
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Maybe its just folklore, I have heard that he never wanted to patent any of his ideas, just to further mankinds intellect.
 
Archy Styrigg said:
I will build a Tesla Coil someday soon...
Click to expand...

The secondary school I went to had a Tesla coil along with a Wimshurst machine and my favourite a Van de Graaff generator. It was a very old school, the chemistry and physics store rooms were like an Aladdin’s cave for me. I loved physics lessons. Chasing pools of mercury around the bench top was normal*. I even repaired the Wimshurst machine during my lunch breaks.

I can just imagine the HSE’s reaction today. Can’t do that…. Can’t do that…. Can’t do that…. Schoolboys mixed with 500,000V Can’t do that….

* It’s a wonder I’m even alive with some of the stunts we got up to. Pouring ¼LB of mercury from the palm of one hand in to the other.
The only accident I remember was a lad getting to enthusiastic with a burette and sucking sulphuric acid in to his mouth. His dad went mental, not at the school but at his lad for being so stupid. Dad was a research chemist.
 
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Haha...2ndary school 71-8, happy days in the labs!
Burning gas from the taps, dissolving tongs in mixtures of concentrated acids (each bench had 2 or 3 sets of the usual 3), stealing sodium from the stores then burning ones desk back in the classroom, etc... and not a single item of PPE to be seen. We only had a Van d G.


A while back I've been playing with small scale Jacob's Ladders.
Got a 15kV Neon transformer, limited to 20mA, so perfectly safe, unless I'm typing this in hell.
Gap needs to be down to 2 or 3mm before an arc will strike. I really need a pole tranny.
 
trev said:
My kids think me strange but I flippin loved me O level physics lessons
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Physics is brilliant but you need to be seriously clever to go on with it.
Love to have done it but way out of my league beyond school level.
 
Going to start my HND soon but apparently it's the maths that's tough there, good job I was good at that:)
 
trev said:
Going to start my HND soon but apparently it's the maths that's tough there, good job I was good at that:)
Click to expand...


Solving 3rd order differentials will be just a stroll along the Tyne with a bag full of Dog for you then...:shades_smile:
In Electrical? Enjoy & good luck with it anyway.
 
Des 56 said:
For interest I just drew on a piece of paper two magnets with the fields reversing and rotating,do me a favour,when you work out the answer,let me know as well
icon7.png
Click to expand...

This has just about done my brain in!

It’s the only way I can think to get a two phase motor to run in a set direction.

Now don’t forget the original two phase systems used four wires.

The yellow in the drawing is the shading pole. A single loop of insulated copper embedded in the pole face. Blue and red being the phase coils.
View attachment 11549
Any other suggestions gratefully received, however inane.

The rotor is probably totally wrong. I pinched it from a drawing I was doing for three phase motors
 
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As you well know, I'm no motor (dare I use the word) expert!
Does shading reduce the magnetic field in the area where it is?
If so, the machine in your diagram would run anti clockwise, yes?

Remember, he was a genius so there's probably something we don't know.

Nice diagrams, you been on an Autocad course?
 
The shading induces “reluctance” in the magnetic field as far as I remember. IE weakening the field to one side of the pole and giving a kick to the other side. Once the motor is running the shaded pole has little effect. Rotation that depends on the lay out of the rotor.

Please remember, this is from memory and theory. I can’t find anything on the net to back it up.
 
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Tony said:
The shading induces “reluctance” in the magnetic field as far as I remember. IE weakening the field to one side of the pole and giving a kick to the other side. Once the motor is running the shaded pole has little effect. So yes the motor should run counter clockwise.

Please remember, this is from memory and theory. I can’t find anything on the net to back it up.
Click to expand...

We better get advice from elsewhere then. :-)

Mmm...sounds reasonable. Got me thinking about single phase cap run motors, I'll stick with instruments, much easier.
 
Archy Styrigg said:
Nice diagrams, you been on an Autocad course?
Click to expand...

Would love to do “proper” AutoCad drawings. I use AutoSketch. It’s a pig to use, it was written for Windows 3.11 (it’s that old). I have to thrash it in to submission to getting it to run under XP. Like AutoCad it’s capable of minute detail when you zoom in. the motor drawing took about 2 hours and then had to be taken in to Photoshop to colour it.

PS the drawing is wrong, I've only just spotted it. To late to edit.

This is the correct version. See if you can spot the difference.

View attachment 11571
 
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Oh happy days in the physics lab,used to love pouring mercury from one hand to the other,I remember our first day with reactive metals (sodium lithium potassium etc) our physics teacher holds up one hand and says "right lads I know some of you wondered how I lost part of two fingers,well this is how" and proceeded to tell us how when he was at school he had pinched a large chunk of potassium and wrapped it in paper to take home potassium reacts with moist air as well as water and on the way home it rained the stuff ignited in his pocket and he ended up having part of 2 fingers amputated due to severe burns, he finished of with the immortal words"now anyone still feel like sticking a piece in your pocket for later?"Nobody did , we may not have had laptops but by god we made some cracking explosions!
 
A friend owned a little craft shop, she’d made a few enemies along the way.
So I get a phone call one morning;
“Tony, I’ve fond an old rusty tin on the back of a shelf”.
“OK what about it, any label on it?”
“¼oz sodium in vacuum”.
“Don’t touch it, shut the shop, I’ll be there in 20 minutes and I’ll take it to work”.

So at work I taped it to a brick pierced a hole in the tin and slung it in to the drainage sump. Nothing happened, so I’m wandering back to the workshop dejected. While my back was turned there was an almighty explosion, about 100 tonnes of water and quarry slurry erupted like an atomic bomb mushroom cloud. The wind then caught it, the workshop and the plant were a strange brown s*** colour. It took months for the rain to wash it off.
 
Tony said:
A friend owned a little craft shop, she’d made a few enemies along the way.
So I get a phone call one morning;
“Tony, I’ve fond an old rusty tin on the back of a shelf”.
“OK what about it, any label on it?”
“¼oz sodium in vacuum”.
“Don’t touch it, shut the shop, I’ll be there in 20 minutes and I’ll take it to work”.

So at work I taped it to a brick pierced a hole in the tin and slung it in to the drainage sump. Nothing happened, so I’m wandering back to the workshop dejected. While my back was turned there was an almighty explosion, about 100 tonnes of water and quarry slurry erupted like an atomic bomb mushroom cloud. The wind then caught it, the workshop and the plant were a strange brown s*** colour. It took months for the rain to wash it off.
Click to expand...
could be a bit interesting if we were to mix then couldn,t it? you know big boys toys and all that lol
 
ringer said:
The lower blue coil was wound the wrong way, which you have now corrected. Motor would stall.
There is another error. Can you spot it?
Click to expand...

Go on you've get me.

PS remember this is theory, I can't find proof of it.
 
Yeh, right OK!

I try my best and what happens.....

I can see your point though but trying to put it right is like trying to plat fog with the drawing package I've got.

But do you think the theory is right?
 
I guess your theory is correct and it is backed up by articles on the net, but then I am not an expert. I would have thought that building shaded poles would be a costly way of doing it. What about adding some capacitance on the supply circuit of one of the phases to start the motor, then removing that capacitance once started?
Before any such control was added to the motor, perhaps they just mechanically started the motor in the required direction?
 
Two phase didn’t last long commercially, it was used a bit in Buffalo NYS. Soon superseded by three phase thank god. So with it’s short life not a lot of info around.
 
Re: Rotation of 2 phase motor...

Had a think and come up with this... (borrowed your drawing Tony)

2 phase motor.jpg

2 phases 90[SUP]o[/SUP] out from each other.
If p1 is connected to coil A, p2 to coil B & neutrals out from C & D then the flux peak will rotate clockwise, motor runs clockwise.
If p1 is connected to coil A, p2 to coil D & neutrals out from C & B then the flux peak will rotate anticlockwise, motor runs anticlockwise.

(Prepares to be ripped to shreds...) :38:



edit, still think this is wrong though!
 
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Tony said:
This has just about done my brain in!

It’s the only way I can think to get a two phase motor to run in a set direction.

Now don’t forget the original two phase systems used four wires.

The yellow in the drawing is the shading pole. A single loop of insulated copper embedded in the pole face. Blue and red being the phase coils.
View attachment 11549
Any other suggestions gratefully received, however inane.

The rotor is probably totally wrong. I pinched it from a drawing I was doing for three phase motors
Click to expand...


Hi Tony

Interesting question, been giving it some thought (and some reading on the net) and what I think is that Tesla developed the ‘Rotating magnetic field theory’ and using this he built a generator, and a two phase motor, I don’t know how he excited the generator but once it was going and the motor connected, the motor just followed the rotating field around.

Way back then he probably didn’t care which way it was going, as long as it was going, to reverse direction he probably swapped the connections or ran the generator in the opposite direction.

I should imagine it was a lot later, when the idea was more developed and the motor being put to practical use, that he needed to worry about how to fix the direction, maybe he thought about a starting winding later, or maybe someone else did, I've read that he sold the patent to Westinghouse for $65000.

So I don’t think that the motor in your excellent video was capable of running in a fixed direction, but then it wasn’t supplied from a networked power supply.
 
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Now you’ve got me thinking. Going to have to superimpose two sine waves 90° out of sync with each other.

Found a better way.

Blue (N) and Purple (S) Phase 1
Red (N) and Green (S) Phase 2

The length of the bars represent the strength of the field. So yes you do get a rotating field.

That’s chucked all my theories out the window.

View attachment 11615

So the motor drawing should be like this

View attachment 11616
 
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My brain hurts now :dizzy2: and I'm tired from trying to resist replying to another thread this afternoon. :)
Work it out so I can stop thinking about it!
 
Well, that's a completely useless piece of knowledge I've gained there!

Good thread Tony, bring on the next one.
 

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