In message , Craig Carmichael
craig@saers.com> writes
>For my axial flux "Electric Hubcap" motors (36V, 4.6KW 0-2000 RPM...)
>I use a separate 2" O.D. x 1" thick iron powder toroidal core for
>each coil. (Unlike typical usage, my coil is wound as a doughnut
>around the outside, the wires epoxied with heat conductive epoxy.)
>These donut coils are individually attached in a ring to non-metallic
>(molded PP-epoxy) body parts with no electromagnetic drag. At 2000
>RPM the frequency is just 100Hz, so high frequency losses don't come
>into play. It's almost lossless. Iron losses at 1200 RPM (60Hz)
>calculate as 1W per coil, total 9 watts. No eddy currents because
>every powder particle is insulated from all the others.
>http://www.micrometals.com/ makes them.
>
Hi Craig.
Admittedly the basic commutation frequency is only 100Hz, but do you not
have PWM switching at a much higher frequency to control the motor
power? The class-D power amps I design switch the output H-bridge at
around 300kHz, but that is of course to pass audio signals up to 20kHz.
For a 100Hz output I guess you still have a PWM frequency above the
audio range. (Perhaps at around 25kHz?)
I would have thought this might still give excessive skin-effect and
proximity-effect copper losses in the windings if solid core wire is
used for the coils.
Or are you driving the H-Bridge with a non-PWM signal and doing your
speed control with a buck regulator in the dc feed supply to the
H-bridges?
Thanks,
--
Chris Morriss
| Reply via web post | Reply to sender | Reply to group | Start a New Topic | Messages in this topic (29) |
No comments:
Post a Comment