Report KD 748 about a 16-pole PM-generator available

[Adriaan Kragten]

The new report KD 748 can be copied for free from my website: https://www.kdwindturbines.nl at the menu KD-reports. The title of this report is: "Ideas about a 16-pole radial flux permanent magnet generator with a 3-phase, 1-layer stator with no iron in the coils". I have tried to add figure 1 of this report as an attachment but this doesn't work as the file is probably too large.

[Adriaan Kragten]

I have made a scan of the drawing of figure 1 on 200 dpi instead of 400 dpi and now it is accepted as attachment. The shaft is made out of stainless steel. The armature is made out of mild steel. The bearing covers are made out of aluminium strip size 120 * 20 mm. The stator is cast or 3D printed from synthetic material and so there is no iron in the coils. Therefore there is no cogging torque. The only sticking torque is the bearing friction and the friction of the oil seal. The armature has 16 poles. The stator has a 1-layer, 3-phase winding with four coils per phase. The stator has 12 triangular grooves rounded at the outside and the legs of two coils are placed in one groove. A groove is closed at the inside with a 1.5 mm thick strip with 30° beveled sides. The four bolts M8 which clamp the stator in between the two bearing covers are also used to connect the generator to the generator bracket of the head frame.

[Adriaan Kragten]

I have found some small mistakes in KD 748 which I have corrected. So if someone wants to do something with this idea, please use the latest version.

[Adriaan Kragten]

I have found some small mistakes in KD 748 which I have corrected. So if someone wants to do something with this idea, please use the latest version.

Chapter 4 out of KD 748 describes how the optimum number of turns per coil and the optimum wire thickness can be found for a certain windmill rotor having a certain optimum cubic line. The formula for the optimum cubic line is given as formula 8.1 of report KD 35. As the question about the optimum number of turns per coil has been asked already many times on this forum, one should read this chapter 4 if one has designed a certain PM-generator for a certain windmill rotor.

In the calculation example I have neglected the voltage drop over the rectifier diodes to make the process simple but I think that this is allowed, especially for higher nominal battery voltages than 12 V. Formula 13 of KD 340 gives the DC voltage for star rectification if the voltage drop over the rectifier diodes is neglected. Formula 14 of KD 340 gives the DC voltage if the voltage drop over the rectifier diodes is taken into account. As the unloaded AC voltage at a certain rotational speed is proportional to the number of turns per coil, formula 13 gives a linear relation in between the number of turns per coil and the DC voltage.