Honk
100 W
- Joined
- Oct 10, 2011
- Messages
- 230
Hi.
I have bought an Ampflow A40-300 that I would like to rebuild for lower KV. Originally it's 167KV (4000RPM at 24V).
As I want to keep the copper resistance at 50mR I don't want to rewind it (pain in the !!! as it is glued hard)
So I was thinking about replacing the ferrite magnets by stronger NdFeb.
It will take thicker back iron to handle the flux but that is no problem as I have access to a machine shop.
I have disassembled it to get the measurements needed and to calculate the new magnets size. See the pics.
But it seems I'm limited to less flux increase than desired as the teeth arms seem somewhat to thin.
It might be that the motor is optimized for the ferrites and swapping to NdFeb won't yield much of an improvement.
I have measured an airgap flux of 0.334T by my gaussmeter in between the teeth faces and ferrite magnets.
According to my findings it looks as the thin arms (2.9mm wide) limits the flux to 0.56T at the teeth face (8.5mm wide).
As magnetic flux is concentrated by the change in width ratio it would come to an increase of max 2.93 times.
Simply put: 8.5mm teeth face / 2.9mm arm = 2.93 times flux concentration.
2.93 x 0.56T teeth = 1.64T in the arms, which is just about what silicon steel can handle before heavy saturation.
Going from 0.334T to 0.56T isn't much of an improvement. Only 1.677 times higher flux which points to an KV at approx 99.
I would prefer lower KV to hit my goal with less design effort on the other parts.
Am I right here or possibly wrong so there is room for more improvement?
I have attached disassembled motor pictures, PDF layout and Autocad files that could be imported by FEMM.
I'm no master myself of FEMM (I simply don't know how to get started...very strange interface) but perhaps some
nice guy or girl could import and simulate the A40-300 with both Ferrite and NdFeb's?
Have a look and tell what you think!!!
I have bought an Ampflow A40-300 that I would like to rebuild for lower KV. Originally it's 167KV (4000RPM at 24V).
As I want to keep the copper resistance at 50mR I don't want to rewind it (pain in the !!! as it is glued hard)
So I was thinking about replacing the ferrite magnets by stronger NdFeb.
It will take thicker back iron to handle the flux but that is no problem as I have access to a machine shop.
I have disassembled it to get the measurements needed and to calculate the new magnets size. See the pics.
But it seems I'm limited to less flux increase than desired as the teeth arms seem somewhat to thin.
It might be that the motor is optimized for the ferrites and swapping to NdFeb won't yield much of an improvement.
I have measured an airgap flux of 0.334T by my gaussmeter in between the teeth faces and ferrite magnets.
According to my findings it looks as the thin arms (2.9mm wide) limits the flux to 0.56T at the teeth face (8.5mm wide).
As magnetic flux is concentrated by the change in width ratio it would come to an increase of max 2.93 times.
Simply put: 8.5mm teeth face / 2.9mm arm = 2.93 times flux concentration.
2.93 x 0.56T teeth = 1.64T in the arms, which is just about what silicon steel can handle before heavy saturation.
Going from 0.334T to 0.56T isn't much of an improvement. Only 1.677 times higher flux which points to an KV at approx 99.
I would prefer lower KV to hit my goal with less design effort on the other parts.
Am I right here or possibly wrong so there is room for more improvement?
I have attached disassembled motor pictures, PDF layout and Autocad files that could be imported by FEMM.
I'm no master myself of FEMM (I simply don't know how to get started...very strange interface) but perhaps some
nice guy or girl could import and simulate the A40-300 with both Ferrite and NdFeb's?
Have a look and tell what you think!!!