[Prev][Next][Index][Thread]

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