Servo disk motors for rotary spark gaps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Scott Hanson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <huil888-at-surfside-dot-net>

Ken -

How long does the first revolution take, from a dead stop? Literally
milliseconds, depending on the size of the motor. Because the armature
consists only of a very thin disk of copper conductors, with absolutely no
iron core or laminations of any sort, the armature mass is a tiny fraction
of the mass of any conventional AC or DC motor. In fact, the motor shaft
itself can have more mass than the rest of the armature.

Also, because of the lack of discrete iron poles in the armature, these
motors have almost no "cogging" at low speed. The lack of iron means no
inductive spikes during commutation, and no arcing or burning of the brush
and commutator surfaces. These motors require only very small brushes and
commutator surfaces. A 1/2 HP motor of this type has tiny brushes, and will
run with hydraulic smoothness at only a few RPM with only 2 volts applied.
During full acceleration they can draw 50A or more.

Lots of these motors are now available on the surplus market, and many of
them are equipped with high resolution optical encoders for precise speed
control.

These encoder-equipped motors could be used with an external feedback
control circuit as an "electronically controlled" synchronous rotary spark
gap motor, as opposed to a modified (salient pole) induction motor that
achieves its synchronism internally via "electromagnetic control".

Regards,
Scott Hanson

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, June 01, 2003 3:43 PM
Subject: Re: Need a variable-speed 2hp or greater AC motor for serious gap
drive


 > Original poster: "Crow Leader by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<tesla-at-lists.symmetric-dot-net>
 >
 >  > Original poster: "Scott Hanson by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <huil888-at-surfside-dot-net>
 >
 > [cut]
 >
 >  > Also, there are large number of high-performance, ironless-core DC
servo
 >  > motors (Servo Disk type) on the surplus market now (ex-computer tape
drive
 >  > or large disk drive) that can accelerate from a dead stop to over 5,000
 > RPM
 >  > in less than 1 revolution. This type of acceleration can destroy
 > couplings,
 >
 > How long does this first revolution take?
 >
 > KEN
 >
 >