Tinman's Rotary Transformer

[tim123]

Hi Tinman,
  just seen the new vid. Nice and clear. Looking forward to the next... Not sure I understand the need for rewiring the stators though...

(Update: Rewatched the vid - I see your motor has 1/2 the windings on each side - that's why. Neither of mine have that arrangement - they're just single coils each side...)

Today's progress:
- Drilled the rivets out of my motor. It was easy.
- Took the motor apart. Easy.
- Separated the 2 stator coils by snipping them in the middle, then feeding the extra ends out. Easy
- Dropped the rotor. All too easy.
- Bought some bolts
- Re-assembled motor.
- Discovered I had broken the rotor when I dropped it.

Before I dropped the rotor I measured the resistance between the segments. They were all the same! (2.2 Ohms) After the drop, the values were all different - so it must've shorted out inside.

I discovered that the rotor doesn't work the way I thought it did:
- The rotor coils are not separate - they're all one big coil.
- It doesn't pulse individual rotor coils, powering up & down
- The brushes effectively separate the one big coil into 2 coils of opposite polarity.
- So all the rotor copper has current flowing in it at all times.
- It's a very clever design.
- They're quite fragile. Don't drop 'em! (D'oh!)

I'm not going to be able to fix the rotor. So, I'll have a look inside the old vacuum cleaner later & see what I can find... The bearing are shot in my washing machine. I may scrap that...

[scratchrobot]

Since i have an old washing machine motor i think i'm gonna try to follow along with this experiment, thanks Tinman and Tim for sharing this.
I don't see the point of unwinding my stator coils because i already have two coils as you can see in the picture i attached?
There is also a reed switch between the stator coils in my motor.

Regards

[tim123]

Ok, I was annoyed with myself for messing up the last one. So I made an extra effort, and now I can report an initial experimental success.

The pic below shows the motor from a vacuum cleaner. The field coils & brushes were all connected in series, so I cut the wires, and fed the extra wire out as before. It's powered (just to the brushes now) with plain DC from a bench power supply.

The motor runs very nicely at 17v, 0.7a

I had to connect both stators in series to get any effect, but now if I take power off via some LEDs, the motor speeds up.

It is not quite the same as TM's because:
- I can't get the stator to put any drag on the rotor (yet)
- I had to use both field coils
- The voltage goes up as the speed goes up (the power supply is keeping the amps constant)

But it's close, and a decent start. The washing machine better watch out...

[tim123]

Now I've had one apart, and I get how the rotor works, I have to revise my principle of operation a bit...

The rotor is fully magnetised by the windings, not just individual segments. This is why there's only 2 large stators in the motor: they create one large field for the rotor to rotate in.

The image below shows the path of the rotor thru the stator.
- The change of polarity, for each segment / winding is (I assume) in the middle of the stator.
- In the standard motor the stator is powered by input DC to a constant polarity.
- In the RT, the stator only powered by Lenz, so it pulses, but still to the same polarity...
- The rotor is attracted to the center of the stator, at which point, it reverses polarity
- The rotor segments leaving the stator are thus repelled by the stator.

The reason why the RT works is this:
- As the change-over segment swaps polarity, the field coils see a loss of flux ('N' in the drawing)
- The coils produce EMF - resulting in a magnetic field of the *same* polarity.
- So the coils act as if they were powered - for free.


Tim

PS. I think this means it should be possible to use permanent magnets to power the rotor (indirectly, will work on a pic). Which would mean proper OU...

[tim123]

Here's an idea... Using the same principle, but with PMs to polarise the rotor segments...

- The stator & PM are all fixed.
- The rotor is just magnetic steel segments
- The rotor segments extend the field of the PM they are over
- When the segment crosses the center-line / change-over point it loses/changes it's polarity, just like in the powered version.
- The coil / stator reacts just the same - with a pulsing field.
- So the stator attracts & repels the rotor segments - as if it was powered.

What do you think?