Re: ASYNC and SYNC???????

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Tyler,

	A synchronous motor's rotation is exactly tied to the AC line sine wave.
When the line signal has a peak, the motor shaft will always be in the same
position at that moment.  Thus you can use it to trigger the gap exactly in
step with the AC line signal.  These are also referred to as salient pole
synchronous motors.

There are some motors that are also synchronous but can lock on at any
position.  There are non-salient pole synchronous motors.  These are used
commercially but should be avoided for our uses.  Since the sync position
changes whenever the motor is started, they always have to be adjusted each
time which is a bother.

Async motors are everything else.  The common 1725 motors are close but the
position is always slipping in relation to the AC line.  There are also
variable speed DC motors that go from 0 to like 10,000 RPM some people have
used to experiment with different break rates.  If the speeds are
approximately the same, sync motors will deliver twice the power of an
async motor since it can always hit at the optimum time.

I assume you want a salient pole sync motor for 120BPS use (that's what
most people want).  It is best to simply convert a common 1725 RPM  1/4 HP
AC blower motor.  They are very common new and used.  If you have not
already seen the "plans" for this conversion, see:

http://users.better-dot-org/tfritz/syncmot.zip

Be sure to ask questions since these plans are a bit confusing the first time.

Cheers,

	Terry

>At 10:08 PM 10/7/2000 -0600, you wrote: 
>What is the diference between sync and async for a RSG.   I am curently 
>looking for a motor to convert into a RSG and will be modifying it to be 
>sync but maybe i need it to be async.   any info you can give would be 
>great. Also if anyone has a pre modified motor they would like to sell, I 
>may be interested.
> 
>Thanks all
>tsgeoman-at-uswest-dot-net
>Tyler
>