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Re: DC supply

Subject: 
        Re: DC supply
  Date: 
        Sat, 29 Mar 1997 11:33:34 -0500 (EST)
  From: 
        richard hull <rhull-at-richmond.infi-dot-net>
    To: 
        Tesla List <tesla-at-pupman-dot-com>


At 10:49 PM 3/27/97 -0600, you wrote:
>Subject: 
>        DC supply
>  Date: 
>        Thu, 27 Mar 1997 09:58:10 -0500
>  From: 
>        chuck seguin <seguinc-at-algonquinc.on.ca>
>    To: 
>        Tesla List <tesla-at-pupman-dot-com>
>
>
>Good morning everyone,
>
>Here is a question that puzzles me.
>
>I have aquired a great XFMR from friends at a local college.  It was
>used, at the time, for a TEA laser power supply.  It's a 30 kV -at- ? mA. 
>The interesting portion of this is the fact its a DC supply.  It's got a
>full wave bridge connected accross the output.  The whole thing is
>submerged in XFMR oil.  Now the question: can I use a DC supply
>appropriatly to operate a large system, or small one at that?

DC supplies are Ideal in a number of ways and a pain in some other
respects.
With a full way rectifier and no filter cap you have undirectional
firing
available at the peak of the sine 120 times/second.  A smart man will
fire
much more often than this.

There is little advantage in such a supply over the common AC
transformer
other than the cap is never reverse charged and some stress is removed
from
the transformer and the cap (big deal).

With the big "?" in your current (I) knowledge of the system, you may
instantly blow the thing if you try and use it for Tesla work.  A large
HV
choke is a must have item in such a supply, and a limiting resistor
would be
nice too until you have a feel for what's going on.  That is as detail
as
you can have with the "?"
R. Hull



>
>Another question.
>Why is a synchronous, rotary, gap called that way?
>My studies indicate that the best time to fire the gap is at the peak of
>the AC waveform, to transfer the max energy.



Theoretically, you are correct, but tremendous additional energy is
being
overlooked on each side of the sine.  John Freau had a great Idea for a
synchronous gap which fired three or more times about the peak of the
sine.
R. Hull



  How is this accomplished
>when you have a rotating gap that is started (the motor that is) at we
>don't know when, on the AC waveform?  Or do we have something that does
>"synchronize" the firing of the gap with the peak of the AC waveform.




You can't ever know where the sine is when you crank the system up.  All
synchronous motors will lock to the line frequency!  The salient pole
version (a grossly inefficient form of Synchronous motor) with lock to
the
same point of its rotation every single time you turn it on.  Every
synchronous motor regardless of design will have to have a scheme
whereby
either the motor or the outer fixed electrodes must be rotatable WHILE
IN
FULL OPERATION in order to align the firing point of the gaps with the
peak
of the sine.  (Motor is made rotatable in most all scenarios) No fancy
test
gear is needed!  You will realize when the system is in sync. (By using
that
ultimate integrating engine and feedback mechanism of the eye-brain
combo.)

Here is where the salient pole motor is handy.  Once set, and locked
into
place it need never be adjusted again.  With a the more efficient
standard
synchronous motor, you will have to seek the optimum firing point every
time
you turn on power.  Also, you must allow for 180 degrees of free
rotation here.

This will also work with unfiltered DC as well.  Good luck.
R. Hull TCBOR


>
>The two questions do relate, for me.  If I use a DC power supply (full
>wave rectification actually) how will a fire the gap appropriatly
>
>Thanks in advance.
>
>Chuck
>
>