# Axial-flux stator plates: Ø90 9-coil and Ø70 6-coil

> How do I wire a 9-coil 3-phase axial flux stator?

- Category: Stirling engines › Generators & instruments
- Kind: Hardware
- Basis: Coreless 3-phase stator: coils = 3/4 of poles (12 pole / 9 coil, 8 pole / 6 coil), Ø13 pockets for the bobbin flanges, M3 holes at ISO 273 clearance
- Page: https://xemstudio.com/objects/axial-flux-stator/ · JSON: https://xemstudio.com/api/geometry?object=axial-flux-stator · Plain text: https://xemstudio.com/objects/axial-flux-stator/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- The Ø90 stator is a 4 mm plate with 9 Ø13 through pockets on a Ø72 circle, a Ø14 centre hole the Ø8 shaft passes without contact, and 3 × Ø3.4 (M3) mounting holes on a Ø86 circle.
- The Ø70 stator has 6 Ø13 pockets on a Ø52 circle, the same Ø14 centre hole and 3 × Ø3.4 holes on a Ø66 circle.
- The pockets take the Ø13 flanges of the coil bobbin (slide).
- Wire 3-phase by series groups: on 9 coils 1-4-7, 2-5-8, 3-6-9; on 6 coils 1-4, 2-5, 3-6; rectify with a 3-phase bridge.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| centre hole | Ø14 | shaft passes clear (no contact) | designed | stator-* |
| coil pockets | Ø20 | bobbin flange Ø20 | slide | stator-* |
| mounting holes | Ø3.4 | M3 screw clearance | designed | stator-* |
| coil-to-rotor air gap | 1.5 each side (8 stator and bobbin, rotor faces 11 apart) | rotor magnet face | designed | stator-* |

## Sizes

| stator | plate_mm | coils | coil_circle_mm | centre_hole_mm | mount_holes |
|---|---|---|---|---|---|
| stator-90-9coil | Ø90 × 4 | 9 | 72 | 14 | 3 × Ø3.4 on Ø86 |
| stator-70-6coil | Ø70 × 4 | 6 | 52 | 14 | 3 × Ø3.4 on Ø66 |

## Where the files are

- Wikipedia: [Axial flux motor](https://en.wikipedia.org/wiki/Axial_flux_motor) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Alternator](https://en.wikipedia.org/wiki/Alternator) — web — CC BY-SA 4.0 (text)
- Hugh Piggott: [A Wind Turbine Recipe Book (axial-flux alternator design)](http://scoraigwind.co.uk/) — web, PDF — Author's site (verify at link)
- Long Earth Society: [Engine and rig builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/axial-flux-stator/index.json

- stator-90-9coil: [STEP](https://xemstudio.com/files/hardware/axial-flux-generator-kit/stator-90-9coil.step) · [STL](https://xemstudio.com/files/hardware/axial-flux-generator-kit/stator-90-9coil.stl) — stator plate Ø90 × 8: 9 Ø20 coil pockets on a 66 mm circle (3-phase, 12 pole / 9 slot), Ø14 centre hole (shaft passes clear), 3 × Ø3.4 (M3 clearance) mounting holes on an 82 mm circle (2.3 mm wall to the rim)
- stator-70-6coil: [STEP](https://xemstudio.com/files/hardware/axial-flux-generator-kit/stator-70-6coil.step) · [STL](https://xemstudio.com/files/hardware/axial-flux-generator-kit/stator-70-6coil.stl) — stator plate Ø70 × 8: 6 Ø20 coil pockets on a 46 mm circle (8 pole / 6 slot), Ø14 centre hole, 3 × Ø3.4 mounting holes on a 62 mm circle (2.3 mm wall to the rim)

## How it fits

### Connects to
- [Coil bobbin Ø10 core × 8 mm, Ø13 flanges](https://xemstudio.com/objects/coil-bobbin/): Ø13 bobbin flanges in the Ø13 pockets (slide)
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/): M3 through the Ø3.4 mounting holes

### Also needed
- [Axial-flux rotor plates: Ø90 with 12 magnets (Ø8 bore), Ø70 with 8 magnets (Ø5 bore)](https://xemstudio.com/objects/axial-flux-rotor/): magnets on the same Ø72 / Ø52 circle

## Questions

**How do I wire a 9-coil stator for 3-phase?**

Coils 1-4-7, 2-5-8 and 3-6-9 each in series as the three phases, then a 3-phase bridge rectifier.

**Does the shaft touch the stator?**

No; the centre hole is Ø14 around the Ø8 shaft, so the stator is fixed to the frame by its three M3 holes.

## Fits with

- [Axial-flux rotor plates: Ø90 with 12 magnets (Ø8 bore), Ø70 with 8 magnets (Ø5 bore)](https://xemstudio.com/objects/axial-flux-rotor/)
- [Coil bobbin Ø10 core × 8 mm, Ø13 flanges](https://xemstudio.com/objects/coil-bobbin/)
- [Hall sensor mount for TO-92S (A3144 / SS49E)](https://xemstudio.com/objects/hall-sensor-mount/)
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/)