B
Bill Sloman
Guest
On Wednesday, 10 December 2014 22:59:14 UTC+11, alb wrote:
<snip>
High frequency current in the motor coils induce high frequency currents in the motor magnetic path, which warm the rotor (and decrease it's magnetic permeability) without doing anything useful.
I've never been sufficiently involved to need to run the numbers, but the different between magnetic core materials for different frequencies is that the higher bulk resistance materials are more suitable for higher frequency applications - laminated iron cores for 50/60Hz mains distribution, powder iron cores for higher frequencies, manganese-zinc ferrites for up to about 100kHz and the higher resistivity nickel-zinc ferrite for use up to about 10MHz.
The 3kHz limit could reflect the nature of the rotating component in the particular motor.
--
Bill Sloman, Sydney
Hi Tim, followed your suggestion I post on s.e.d. including the OP and
your reply for clarity. Please see at the bottom my answer to your
message.
<snip>
Valid point on the switching spikes! Sure we can sample when we expect
*not* to have spikes. What really drives the cutoff frequency? The
customer asked for 3KHz, but in the end I do not understand what is the
motivation.
High frequency current in the motor coils induce high frequency currents in the motor magnetic path, which warm the rotor (and decrease it's magnetic permeability) without doing anything useful.
I've never been sufficiently involved to need to run the numbers, but the different between magnetic core materials for different frequencies is that the higher bulk resistance materials are more suitable for higher frequency applications - laminated iron cores for 50/60Hz mains distribution, powder iron cores for higher frequencies, manganese-zinc ferrites for up to about 100kHz and the higher resistivity nickel-zinc ferrite for use up to about 10MHz.
The 3kHz limit could reflect the nature of the rotating component in the particular motor.
--
Bill Sloman, Sydney