RE: MOT Mutual inductance with DC PSU's

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>


Ted:

I have not found the same thing.  My PSU is (4) MOT's parallel primaries
series secondaries.  The secondary is grounded between the 2nd and 3rd
MOT so I have two AC legs 180 deg out of phase at ~4000 VAC feeding a FW
Rectifier with ~1uF capacitor strings between each DC leg and ground.
Thus DC output is ~ +6000 VDC one leg and -6000 VDC the other leg. My
charging reactor is 36 H and my tank cap is ~ 40 nF.

The MOT primary is current limited by an adjustable inductor(currently
set at 15 mH).  All MOT's still have their shunts.  With the CR(15 mH) I
pull 17 amps when operating the coil feeding the CR 120VAC(MOT's see ~90
to 100 VAC).

Without the CR and the MOT's dead short I pull in excess of 75 amps.
Achieved as high a 30 amp draw by reducing CR inductance.  Haven't
pushed farther due to concern about blowing capacitor.  See
www.teslaboys.com for pictures.

Mark R Dunn, P.E.
Engineering Manager
Wm. W. Meyer & Sons, Inc.
847-673-0312 x244



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Thursday, January 12, 2006 1:23 PM
To: tesla@xxxxxxxxxx
Subject: MOT Mutual inductance with DC PSU's


Original poster: tesla <tesla@xxxxxxxxxxxxxxx>

Hi Team

Looking for confirming comments on a problem I've been experiencing with
a larger DC resonant charging MOT system I'm trying to get going. (90nF
CP and 30Hy Charging inductance from 6 gapped MOT's (2 in parallel of 3
in series
config)

I've configured an earlier 4 (or 6 if extra MOT's are added) MOT stack
AC system to run as DC with a FW bridge into DC Filter of 1.25 uF using
20 MWO caps (across the plus to minus whole 12kv developed at the bridge
O/P)

I've found the system will not draw much current into the Coil. I've
concluded that the Magnetic shunts in the MOT's is adding so much O/P L
to the system that large O/P inductive reactance of the MOT PSU iteself
adds too much current limiting impedance in a system that requires brief
pulses to charge the filter caps.

I've noticed in the past that MOT stacks pull much more mains current
into a very capacitive load and I've always theorised that his was due
to cancellation of the very inductive O/P Z of the MOT's due to the
magnetic shunts.

I've removed the magnetic shunts from a MOT and the reduction of
effective O/P Z is dramatic and I believe that charging Caps via a
rectifier system is best done with magnetic shunts removed in the MOT's.
Has anybody experience with this situation ?. The primary current on a
MOT with a SC secondary with the shunts removed is at least 4 times the
current with the magnetic shunts in place.

Ta
Ted L in NZ