# sinewave BLDC motors

Discussion in 'Electronic Design' started by colin, Jun 16, 2007.

1. ### colinGuest

Hi
another look at at trying to get a smoother high speed motor,
Im using a motor out of a old large disc drive wich generates a modified
trapezoid signal
my idea atm is to remagnetize the rotor so it is much more of a sinewave,
ive managed to remagnetize it with a different number of poles before
using a few turns of wire on a iron slug wich fits neetly inside the rotor,
and 2 big 450v electrolytics in series and a BIG microwsitch.

so im thinking of having more turns spread out to magnetise it with a less
abrupt transition between poles,
however if the magnetising current is too high it will simply clip and cuase
the same result,
so my next idea is to have the wire at an angle so the transition is

my question is wich would be best, to put the wire at a straight angle like
a series of triangles
or try and mimic a sinewave ?

the rotor has 4 pole pairs, the stator has 6 segments, with tiny segments
inbetween each one, im a bit baffled as to what those are for.

although theres something like a bell ringing in my head thinking of my
electric machines lectures decades ago,
but all I can remember is compensating windings to stop comutator flashover,
but this is brushless.

Colin =^.^=

2. ### colinGuest

well ive had some succes so far, I wound magentizing coil in the shape of a
trapezoid and the
cogging was reduced, the open circuit voltage was also cleaner, wel at least
the common to phase was certainly better
, actually it realy did look much like the shape of the coil, now what a
surprise ! i tried with a few different slopes etc too.

however the phase to phase voltage looked realy odd, so it looks like il
have to try and get the coil in the shape of a good sinewave ... i gues the
phase to phase picks out the distortions. just tricky trying to get a good
sinewave and keep it in place.

Colin =^.^=