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Old 18th July 2010, 05:33 PM   #31
Few is offline Few  United States
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Quote:
I remember Roger Sanders used to publish all his designs with PSM, but he seems to be using insulated wires (not PVC stranded) for his commercial products.
Does that not suggest a performance advantage ?
Sanders is using copper clad board---printed circuit board material---milled with a CNC machine for his latest products. I don't recall him ever using insulated wires.

There are advantages and disadvantages to each of the popular stator constructions. You just have to choose your priorities: ease of construction, ease of breaking the stator into electrically isolated segments, ease of insulation, visual transparency,... I don't think there is a single approach that is best in all situations. If there were, nearly everyone would just adopt it.

Few
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Old 19th July 2010, 04:37 AM   #32
mavric is offline mavric  United States
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Default Build one

I have posted a complete start to finish esl. now that this is going, I would be more than happy to get started instead of the he said she said stuff. Give me some measurements, some ideas, turn me loose and you will see a floor to ceiling wire stator.
I have the measurements but some better pics would help. I am having problems with the wire gig, not sure if to cut each one and then stretch all at the same time. I hate speculating so info would be nice now.
I will post pics of my gig, and i guess go from there.
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Old 19th July 2010, 08:42 AM   #33
Calvin is offline Calvin  Germany
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Hi,

There´s powdercoating and than there´s powdercoating
A single coating layer formed by electrostatic spray coating will most definitely not be sufficient.
The process of manufacture is as such:
The cold metal sheet is hung upon a rig. It then is connected to a charged coating pistol. The coater coats the metal sheet with the powder which holds to the metal sheet because of the charging. The metal sheet is then put into an oven and the powder melts. After cooling down the metal sheet is ready. You may reach up to 100µm of layer thickness with this kind of coating technique. So You need at least a double layer coating or even a triple layer coating to reach a sufficiently thick insulative layer for ESL usage. Since the powder needs to be melted a second or even third layer is obviously difficult to do, because all layers need to be melted completely but must not be allowed to flow. A possible solution is to use different powders whith the second layer powder having a lower melting point than the first. Since You want powders with certain electrical parameter values it may be hard to find suitable powder-combinations.

The second way which looks much more promising on first glance is the electrostatically assisted fluidized bed coating. The process of manufacture is as such:
The powder is filled into a trough. Air is blown through openings from below into the trough. Now the powder behaves like a liquid. The metal sheet is heated up above the melting point of the powder. Now it is dipped into the powder which ´flows´ around the metal sheet. The powder melts and sticks to the metal sheet. After withdrawel and cooling the sheet is finished. Layer thicknesses of up to 100µm are possible within just one working cycle. But -and this is a big But- since the punched metal sheet mostly consists of holes there is not enough mass i.e. heat capacitance. The sheet cools down more quickly than the powder needs time to melt completely. The coater may use a second heating cycle in an oven, but basically this technique doesn´t lead to firstclass results (pinhole free).

The probabely best solution is a 3-layer combination of spray powder-coating and spray wet-coating. First coat is a single or double layer of powder as thick as possible (~100m-150µm) using electrostatically assisted spray coating.
The intermediate layer could be a thin colour-defining wet coating. The top layer could be from single- to quadruple-built (transparent) wet coating.
This way to coat is quite complicated and expensive but allows for nearly any color You wish and allows to use optimized materials for each layer.
The first layer may be optimized for electrical parameters and edge covering, the intermediate layer for optics and the outer layer for optics and mechanical robustness. Final coating thickness can reach 300µm and more.

The big problem with all coatings where heat/melting is involved in the coating process are the sharp hole edges. Besides the possibility of microcracks developing in the coating material when the hot powder layer cools down and shrinks, the layer thickness at the edge is minimal. So the first layer of powder needs to be chosen to allow for thick edge covering (smallest radii of constant layer thickness, a parameter seldom mentioned in the datasheets. Nylon beeing one of the best with an radii-value of 4mm).
If a punched metal sheet is not deburred or preferably has rounded edges You should at least calculate with double the layer thickness on the surface than needed.

Using powdercoating techniques the results may vary from completely useless to absolutely excellent. Powdercoating alone will hardly be sufficient. Powdercoating as part of an advanced coating process can be very good.

jauu
Calvin
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Old 19th July 2010, 08:17 PM   #34
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Originally Posted by alexberg View Post
I have found hookup wire by Belden #8076 polyester inside, amide/imide jacket. BV=5600. Is it suitable for wire stator?
Yes, this wire would be suitable for wire stators.
But, remember that with magnet wire you should not stretch the wire the way you do with PVC insulated wire.
With magnet wire, only hold the manufacturer's recommended tension when gluing to stators. If you stretch magnet wire, cracks will form in the thin insulation.

Attached is the recommended winding tension for Essex magnet wire. I'm sure the Belden wire is similar.
Attached Files
File Type: pdf Exxex_tension.pdf (26.8 KB, 59 views)
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Old 20th July 2010, 06:58 AM   #35
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bolserst,

those winding tensions are considering safe coil winding at high speed without the risque of cracking wires.

If you do static tensioning it can be tensioned further. The PU insulation should be capable to be stretched about 10% as well.

Capaciti
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Old 20th July 2010, 02:48 PM   #36
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Quote:
Originally Posted by Capaciti View Post
those winding tensions are considering safe coil winding at high speed without the risque of cracking wires.

If you do static tensioning it can be tensioned further. The PU insulation should be capable to be stretched about 10% as well.
Hi Capaciti,

Have you built stators with stretched magnet wire?
I tried 4 times and all stators had numerous hair fine cracks in the insulation after stretching. They were difficult to see without a magnifying glass. But, moving a round metal bar with high voltage applied would arc when brought near the cracks. This was why I recommended staying close to the safe winding tensions published for electric motor winding to avoid insulation cracking.

For reference, I used Essex Superior AWG20-200C-11 wire on original factory spool.
Insulation type: modified polyester base coat and an improved polyamideimide topcoat

Perhaps I got a bad spool of wire...
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Old 20th July 2010, 04:01 PM   #37
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Quote:
Originally Posted by bolserst View Post
Hi Capaciti,

Have you built stators with stretched magnet wire?

Insulation type: modified polyester base coat and an improved polyamideimide topcoat

Perhaps I got a bad spool of wire...
Most likely not. Permissible elongation is usually 15%. May be it's polyimide, which is rather stiff.
Having wound quite a few power toroidal transformers (up to N*100kHz) I would say that if no interlayer insulation is used, transformer fails over time, though interlayer voltage is quite low.
Alex
P.S. Thanks a lot!
P.P.S. Surprisingly enough I've just asked about the same wire type...
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