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Re: MOT-PSU
There is a standard way to measure transformers to determine the amount of
leakage inductance (for current limiting)..
Step 1.. measure the turns ratio at no load by putting a known voltage in
and measuring the voltage out. Often, you put 110VAC on the HV winding,
and measure the LV winding.
If you can measure the power factor or real power consumed, this is handy
to know too (iron and copper losses).
Step 2... short the secondary with an ammeter. Apply power to the primary
with a variable voltage source until you are drawing the rated current.
Measure the voltage, current, and actual power (or power factor). The
voltage will be much lower than rated input voltage, by the way.
>From all these measurements you can calculate all the transformer
parameters. More at http://home.earthlink-dot-net/~jimlux/hv/xfmrmeas.htm
----------
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: MOT-PSU
> Date: Sunday, August 20, 2000 9:54 AM
>
> Original poster: "Herwig Roscher" <herwig.roscher-at-gmx.de>
>
>
> 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
>
>
>