MOT-PSU

["Herwig Roscher" <herwig.roscher-at-gmx.de> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hello fellow tube coilers,

As I couldn't find a suitable plate xformer for my VTTC, I decided to 
give MOTs a chance. Several coilers had written to the list, that 
MOTs "more or less" are current limited, but I couldn't find any 
"hard" number. Therefore I performed some tests and would like to 
share the results with you:

1. setup:
I connected two MOTs back-to-back and stacked another one for 
higher output voltage. This HV was connected via 2 diodes to a 
load capacitor 32 µF / 6 kVdc (half wave rectifier).  
results:
V in Vdc		I in mAdc		P in W
===============================
5400			---				---
1800			100			180
1380			150			207
1020			200			204

2. setup:
I paralleled the 1st MOT with another one (similar volume/voltage) 
in order to get more current.
results:
V in Vdc		I in mAdc		P in W
===============================
5400			---				---
2460			100			246
1860			150			280
1620			200			324
1440			250			360

3. setup:
Using setup #1 I added another 3 MOTs and 2 diodes to form a 
center tap connection (full wave rectifier).
results:
V in Vdc		I in mAdc		P in W
===============================
5400			---				---
3180			100			320
2400			150			360
1800			200			360
1500			250			375

4. setup:
2 MOTs (similar voltage/volume) back-to-back. Mains input 230 V / 
50 Hz. Vac and Aac measured with analog instruments.
results:
load       load voltage  load current  load power
(Ohms)  (Vac)            (Aac)           (W)
=================================
18  	  95			5.0              475
37.5       140               3.6              504
75          170               2.2              374
150        185               1.2              222
---           190

These results were very dissapointing indeed for my application, 
but now I've a much better feeling what's possible with MOTs and 
what's not.

Regards

Herwig