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Re: Synchronous rotary gaps. - motors
From: Daryl P. Dacko[SMTP:mycrump-at-cris-dot-com]
Sent: Tuesday, September 16, 1997 6:35 AM
To: Tesla List
Subject: Re: Synchronous rotary gaps. - motors
At 03:32 PM 9/14/97 -0500, you wrote:
<big snip>
>>Another idea - I have a pile (3 or 4) of 60 HZ synchros - I know that
>>they run
>>synchronously if you get them spinning. of course these have brushes
>>in them
>>to drive the armature. Also, it owuld seem that a stepper motor could
>>be a
>>good thing - it would be easy to step it in synch with 60HZ.
>>
>I am not aware of any "small" a/c induction sync. motors having brushes
>in them. Repulsion start induction motors have shorting brushes in them
>but are rare. Are you sure they are not a universal series motor?
Synchros are odd cross between a motor and a transformer. Feed them AC
across both sets of armature brushes and tie the three-phase leads
together, and they will transmit any motion of the shafts between the
two units.
With one or two phase-shift caps, they ought to act as nice synchronous
motors.
This might be another good source of sync. motors for gaps ;'}
>Keeping a stepper motor in sync with the a/c line frequency would require
>a solid state driver with an input from the 60 Hz line to lock it in
>sync. The solid state circuit would be in danger form the high voltages
>around the rotary motor disk.>
There is a somewhat rare type of two phase stepper motor that is designed to
run on 60 Hz. AC, by useing a cap to phase-shift the second winding.
Three problems tho,
They usually run at a very low speed, rpm=#teeth in rotor/powerline Hz *60
They don't have much horsepower.
They arn't synchronous with respect to position, they just lock on the the
nearest avalable tooth in the rotor...
I surely agree with the solid state driver, while I'm sure it could be done,
I will bow my head to anyone who can make them work long term in tesla service !
Daryl