RE: [TCML] MOT series

["S&JY" <youngs@xxxxxxxxx>]

Scott,

 

Several of us on the list have measured the no-load current drawn by MOTs as
the primary voltage ramps up.  The below is voltage vs current for 4 MOTs
with primaries in parallel:


70

0.5


80

1


85

2


90

3


95

4


100

5.5


105

7.5


110

10.5


115

14.5


118

17.6

You can see the cores start saturating at about 100 volts, and the current
triples by the time you get to full mains voltage.  Therefore, instead of
running pairs of your MOTs with primaries in series, just keep the voltage
from being more than 100 volts into each primary.  You can do this with a
variac. Or you can modify another MOT by cutting off the secondary and
winding enough turns of #12 or #14 wire to produce 18 volts at 15-20 amps.
Then add this in series-opposing (to subtract 18 volts) in the primary
circuit for your other MOTs.

 

--Steve Y.

 

 

  _____  

From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Scott Bogard
Sent: Saturday, January 01, 2011 1:03 PM
To: Tesla Coil Mailing List
Subject: [TCML] MOT series

 

Greetings everyone,
        Just a thought here, I've been thinking some lately and because MOTs
are so scantily constructed would there be any benefit in using 4 with
two sets of primaries in series, so you end up with only 4kV or 1kV per
MOT.  It seems to me this should keep everything out of saturation, but
I can't help but wonder if the increased primary impedance will lower
current output noticeably.  The other advantage is theoretically one
could get 6kV by using 6 MOTs, and thus be only stressing them 1kV per
MOT on the outer two, which would have their primaries in series, but
parallel with the other 4 MOTs.  Not sure if it is worth the effort but
I have enough MOTs, perhaps I'll try it...

Scott Bogard.
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