Re: High speed induction motor update


"John Larkin" <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:nl2ic35obf4ngko521l24kof449tu6k52t@xxxxxxxxxx
On Sun, 19 Aug 2007 23:31:28 GMT, JosephKK
<joseph_barrett@xxxxxxxxxxxxx> wrote:

colin colin.rowe1@xxxxxxxxxxxxxxxxxx posted to
sci.electronics.design:


"John Larkin" <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote
in message news:da6ec3doukrif950i5869qr2p1tokheo1e@xxxxxxxxxx
On Sat, 18 Aug 2007 10:15:27 GMT, "colin"
<colin.rowe1@xxxxxxxxxxxxxxxxxx> wrote:

Hi,

If anyone remembers I was messing about trying to modify a 2 pole
240vac induction motor to go at higher speed and lower voltage
driven from a d***
based 3ph pwm setup.

well I got some of that magnetic paper wich goes black in the
presence of a
magnetic field,
I put a circle of it in the center of the stator but was very
little to see,
it apears the paper only goes black if the megnetic field goes
perpendicularly through the paper,
wich it doesnt with it aranged this way.

but anyway I had a realy extra strong cup of coffee and traced
how id conected the 4 windings to the 3phase
(there were 16 slots wich made it awkward)
and realised id got one phase backwards.

changing that it now runs at a whoping 20krpm.
it realy starts to sing,
and its not realy balanced well enough as it only made for
1500rpm.

it was only an experiment,
I only put a few turns of wire loosly through the slots,
I also need to bore the rotor out so it can sit in the middle of
a 1M long 12mm dia shaft.
I think I might need to trim the cooling vanes on the rotor too.
however I realy need a motor 2"x2" this one is a bit to big to
fit in easily
at 70x70,
its from an old 8" floppy drive to drive the main spindle.
ive been looking around at all sorts of junk,
but nothing just the right size yet.

my usual stockists only seem to have larger motors.

Colin =^.^=


Modern chem lab centrifuges and turbomolecular vacuum pumps use
magnetic suspension bearings and ac drive. They measure
rotational speeds in kilohertz.


The electronics and software will go to over 100krpm,
its hard to get the moving parts, bearings etc,
to run smoothly enough even at 10krpm.

just getting the shaft straight is taking ages.

Hardly, dental drills and similar have done and do 100,000 rpm for
decades routinely.

Air powered, air bearing PCB drills run up there, too.

yes but they dont have a 12mm dia 1M long shaft.

It probably wouldnt be so difficult if I had an engineering workshop instead
of an electronice workshop lol.

Colin =^.^=


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