Re: MOTs & Thoughts

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

Original poster: "Crow Leader by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

has anybody looked at the current vs. voltage during these tests? Microwave
ovens draw more than 5 amps, so the transfomer being saturated at no load
makes no sense.

KEN

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, July 21, 2002 4:09 PM
Subject: Re: MOTs & Thoughts


> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> Hi Steve,
>
> I tried this too.  Here are the numbers I got with various input voltages
> to my single open loaded MOT:
>
> VAC AAC (true rms)
> 30 0.4
> 40 0.5
> 50 0.6
> 60 0.7
> 70 0.8
> 80 1.0
> 90 1.2
> 100 1.7
> 110 2.7
> 120 4.9
>
> I "think" (but I don't "know") removing the shunts would tend to drive
more
> magnetic flux into the core and make the saturation worse.
>
> Interesting, I didn't realize they saturated so badly...  I wonder if the
> core is less likely to saturate if it had a load on the output?  Or, if
> that makes it worse still...  A PFC cap may also do something "odd"...
>
> This saturation is a big concern in some tube coils and other uses where
we
> want just a "nice" HV transformer.
>
> Cheers,
>
> Terry
>
>
> At 11:49 PM 7/20/2002 -0600, you wrote:
> >I took some no load measurements on a 4 MOT stack that some of you might
> >find interesting.  All 4 MOT primaries are in parallel, and are powered
by a
> >120 volt variac.  Here are no load primary volt vs amp measurements:
> >
> >Volts                    Amps
> >below 75              less than .5
> > 80                         1
> > 95                         2
> > 90                         3
> > 95                         4
> >100                        5.5
> >105                        7.5
> >110                      10.5
> >115                      14.5
> >118 (max)           17.6
> >
> >As you can see, the MOT cores start serious core saturation at around 100
> >volts, or about 85% of their rated voltage.  The moral of this story is
to
> >design your MOT stacks to produce the output you need without exceeding
85
> >or 90% of the normal primary voltage.
> >
> >Question:  Suppose I knock out the magnetic shunts.  Would the above
> >measurements be much different??
> >
> >Another thing to be aware of is that above 90% of normal input voltage
> >causes significantly distorted sine waveforms that sometimes have strange
> >effects on DVMs, causing them to indicate quite inaccurate measurements.
> >
> >--Steve Young
> >
> >
>
>
>