A Thought Experiment

[Sidewinder]

OK, Marvo, I tell you what, I have to work in my workshop Saturday morning.

I have some ABS pieces to turn out on the lathe.

Once I've done this and made them up into what I need to, I'll have a play with a Y/D motor I have there and check your theory, if I have time before Mrs SW calls for Christmas shopping.

I'm not moaning, because I spend so little time with my family due to work, it's like time off for me!!!

In a few weeks, I'll have a TI, so I will then try the other suggestion.

However, a favour please, will someone please remind me Friday PM & Sat AM, UK time, obviously!!!

Thanks.

 

[Marvo]

I'll send you a PM Friday eve.

 

[Marvo]

Yep, I'm not holding out too much hope that it will work in real life, I'd like to try it myself but I don't have easy access to a decent imaging camera unfortunately. In theory it might work but there's numerous real-life reasons I can see that might mean it won't. If the windings can be heated quickly with a fairly large current, maybe somewhere between the normal start and run current of the motor the heat gradients may be fairly well defined, if it's a low current and slow heating the mass of the stator will conduct the heat and the temperature gradient will be ill defined as time goes on.

 

[Sidewinder]

Marvo,

Will you please check your maths from your picture post of the ratio's?

I can't get 6.666 to reduce by a third to 5!

I can't see how:

(6+(2/3)) - ((6+(2/3)*(1/3)) = 5

 

[Marvo]

Lol, I'm not sure where I got that either TBH.

The math may have been a bit shyte but the theory was solid I thought so I reworked it so it's easier to understand hopefully and I've worked it to the point where it's based on a ratio between two test results rather than actual figures so it can be applied to any standard motor. Unfortunately it didn't pan out as hoped but here's the result anyway so at least you can have a snigger.....

 

[Sidewinder]

I went through the theory over the weekend mate, and, came up with the same conclusion, but, I was not prepared to tell you you were wrong, I wanted you to check that I was not wrong!

I made the same mistake early on in my analysis, so once I saw your mistake I thought that you would find it once you reviewed it.

I'll complete my algebraic analysis as soon as I get chance and I'll put it up as a paper.

I can't find an algebraic way of finding a solution using resistance.

However, I'll put up my theory and everyone can check it out.

Good thought experiment so far...

 

[Marvo]

I've got grave doubts you could find an answer with just using electrical tests but I like this kinda thing and I don't even mind being incorrect or wrong TBH, it's interesting to see how different people approach it. I still have the flir method as my current favourite but if I get a chance I might set up my scope over the holidays and see what voltages and maybe harmonics appear on the stator windings when the rotor is manually rotated and whether there may be a way to detect a difference between and internally starred connection and a delta connection..

 

[Sidewinder]

Manator, please do.

I don't have an answer, and I would like to have one.

ANYTHING that can be thrown into the mix that could work then please throw it in.

I'll put my maths analysis up that shows the the R analysis to be incorrect.

 

[Lurch]

Netblind Motor Q.jpg

That's exactly what I did first time round as well, looks so simple on paper. I made a mistake in the sums and divided something by 2 instead of 4 and it looked great!

 

[Rob_the_rich]

I know very little about windings stars and deltas. but I know that if you put a current though a coil you get a magnetic field generated. so if you put a current through all three windings without it spinning, if they are in a star , a bit of metal, or better a magnet, in orbit around the motor would only feel North (or south) all the wat round.

if it is in a delta the magnet would feel N-S-N-S-N-S in one orbit.

Does this make sense?