Re: MOT core

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

Original poster: "Virtualgod" <mike.marcum-at-zoomtown-dot-com> 

For 50-60hz transformers, I use sqrt(VA rating)/5.58 to get cross section in
square inches as a starting point. Increasing frequency decreases core size
roughy as an inverse square (4x freq= 1/2 core size, 100x freq= 1/10 core
size, etc). Usually above 2khz ferrite/powdered iron is used as the
laminations get thinner than foil. These are ballpark figures. As for exact
formulas, they're laying around here somewhere...
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, February 02, 2004 7:43 PM
Subject: Re: MOT core


 > Original poster: "Hydrogen18" <hydrogen18-at-hydrogen18-dot-com>
 >
 > Where did you get that formula? How does it include frequenct into the
 > equation? I'd like to use in my transformer calculator I'm developing but
it
 > needs to change with frequency.
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Monday, February 02, 2004 8:58 AM
 > Subject: Re: MOT core
 >
 >
 >  > Original poster: "Richard W." <potluckutk-at-comcast-dot-net>
 >  >
 >  > Actually decreasing the core cross-section by half will drop the power
 >  > capability almost by a factor of 4.
 >  >
 >  > Let's say we have a core who's center leg measures 1" x 2" for 2 square
 >  > inches.
 >  >
 >  > CS = 2 sq.in. (Cross Section)
 >  >
 >  > VA = (CS/0.16)^2
 >  > VA = (2/0.16)^2
 >  > VA = 12.5^2
 >  > VA = 156
 >  >
 >  > Cutting the core in half = 1 sq.in.
 >  >
 >  > VA = (CS/0.16)^2
 >  > VA = (1/0.16)^2
 >  > VA = 6.25^2
 >  > VA = 39
 >  >
 >  > Rick W
 >  > Salt Lake City
 >  >
 >  > ----- Original Message -----
 >  > From: Tesla list <tesla-at-pupman-dot-com>
 >  > To: <tesla-at-pupman-dot-com>
 >  > Sent: Sunday, February 01, 2004 7:34 PM
 >  > Subject: Re: MOT core
 >  >
 >  >
 >  >  > Original poster: "Hydrogen18" <hydrogen18-at-hydrogen18-dot-com>
 >  >  >
 >  >  > The only thing I know to say here is stack the cores. Alternatively
you
 >  >  > could use very small wire for the secondary to achieve the HV
output.
 >  >  > Stacking the cores(inserting 1 E into each end of the "bobbins")
will
 >  > halve
 >  >  > your power output but double your winding window.
 >  >  > ----- Original Message -----
 >  >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  >  > To: <tesla-at-pupman-dot-com>
 >  >  > Sent: Sunday, February 01, 2004 6:49 PM
 >  >  > Subject: MOT core
 >  >  >
 >  >  >
 >  >  >  > Original poster: "Dan" <pbursa-at-cfl.rr-dot-com>
 >  >  >  >
 >  >  >  > Hello !
 >  >  >  > I am curious if someone here has experience with rewinding
microwave
 >  >  >  > transformer.
 >  >  >  > I cut of the I part of the core, removed old windings and split
the
 > E
 >  > core
 >  >  >  > in half so now I have two identical E cores .
 >  >  >  > Together they make 5.5 inches long, 4.15 wide and 1.35 thick core
 > with
 >  >  >  > about 1.72 square inches area...
 >  >  >  > This looks like I'll need over 400 turns on primary... this would
 >  > require
 >  >  >  > 40000 turns for 12KV secondary and there is not enough space for
 > this,
 >  > I'm
 >  >  >  > afraid.
 >  >  >  > My question is - if I use less primary windings (say 150 - 200),
how
 > it
 >  >  >  > affect performance, core saturation, ...
 >  >  >  > I noticed that original MOTs primary was also less than proper
 > amount
 >  > of
 >  >  > turns.
 >  >  >  > Also, since MOT core is welded together, how the weld affect the
 > core
 >  >  >  > losses and eddy currents? isn't the very purpose of using
laminated
 >  > core
 >  >  > to
 >  >  >  > minimize these loses ?
 >  >  >  > How about potting finished transformer in oil ?
 >  >  >  > Thank you in advance
 >  >  >  > Vladan
 >  >  >  >
 >  >  >  >
 >  >  >  >
 >  >  >
 >  >  >
 >  >
 >
 >