| Electronics > Projects, Designs, and Technical Stuff |
| High temperature thin dielectric or insulating coatings for bare copper coils? |
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| magicsmoke:
--- Quote from: Conrad Hoffman on February 09, 2020, 07:36:56 pm ---BTW, can you vacuum impregnate? That helps fill everything for mechanical stability and eliminates air pockets that can encourage arcing. --- End quote --- Yes, I can probably vacuum impregnate. If anyone has any suggestions for vacuum impregnating polyimides I would like to hear their experiences. |
| magicsmoke:
--- Quote from: duak on February 09, 2020, 10:02:13 pm ---Glyptal 1201 is the original product used in electrical equipment and engines but it's only good for 130 C. Motors can be rated for class H which is 180 C winding temperature. Here's a description: "Class H insulation consists of materials such as silicone elastomer and combinations of materials such as mica, glass fibre, asbestos etc., with suitable bonding, impregnating or coating substances such as appropriate silicone resins. Other materials or combinations of materials may be included in this class if by experience or tests they can be shown to be capable of operation at the Class H temperature." --- End quote --- Actually, I am going for a insulation temperature rating higher than class H, 200+ deg. C. Magnet wire with a higher insulation temperature class is pretty easy to source from Superior Essex or REA. |
| magicsmoke:
--- Quote from: trobbins on February 09, 2020, 10:08:21 pm ---Are multiple coils (each of 4-5 turns) located in a slot? --- End quote --- Yes in several of the winding configurations that I am looking at (dual layer fractional slot concentrated windings). --- Quote from: trobbins on February 09, 2020, 10:08:21 pm ---Is the length of turn so long that you really do need thermal transfer in between turns to conduct heat from an enclosed turn? Due to the cross-sectional area of a turn, it appears most heat transfer would be occurring along each copper turn to where you are actively cooling the copper at the ends of the rotor, as compared to through the slot liner, or through presumably an air gap to the stator? --- End quote --- --- Quote from: trobbins on February 09, 2020, 10:08:21 pm ---I am most likely going to just rely on spray cooling of the end turns. This is typically what is done in high performance electric vehicle motors and aerospace machines. It has quite good heat transfer capabilites and if the stack length is moderate it can extract heat from the axial center hot-spots of the windings through thermal conduction along the winding length. It is quite abit more effective than trying to extract heat through the slot liner and lamination. --- End quote --- --- Quote from: trobbins on February 09, 2020, 10:08:21 pm ---With that size of copper, it seems a bit strange from a packing efficiency perspective that you are then requiring such a thin insulation covering. --- End quote --- I need to get the maximum packing factor possible. This is a very high performance machine I am targeting. Every little bit of copper I can stuff into the slot helps. --- Quote from: trobbins on February 09, 2020, 10:08:21 pm ---Are there AC losses in the coil due to some form of switchmode generation of currents? If so, then is that a significant loss contributor due to skin and proximity effects? --- End quote --- Yes, there will be increased AC resistance just because of the high frequency AC excitation (skin and proximity effects). The PWM harmonics will also add additional losses. I am going to try to build in some features to the coil to mitigate these losses. |
| magicsmoke:
--- Quote from: Conrad Hoffman on February 10, 2020, 02:08:52 am ---There are ceramic coatings that can be painted on and fired, also plasma sprayed. I'd start here- https://www.aremco.com/ --- End quote --- Thanks for the tip. |
| trobbins:
--- Quote from: magicsmoke on February 10, 2020, 06:44:12 am ---Yes, there will be increased AC resistance just because of the high frequency AC excitation (skin and proximity effects). The PWM harmonics will also add additional losses. I am going to try to build in some features to the coil to mitigate these losses. --- End quote --- What is your anticipated Rac/Rdc for a coil in the total configuration, and is that consistent with previous test rotors using the same drive waveforms? It seems strange that you haven't described this issue, and only detailed a pedantic need to get the last 0.01% DCR reduction by maxing out the packing factor. |
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