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RE: 4-MOT supply, questions for Mike S.
Original poster: "Michael Strube by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mjstrube-at-earthlink-dot-net>
Hi Steve,
Answers below . . .
-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, December 09, 2002 6:03 PM
To: tesla-at-pupman-dot-com
Subject: Re: 4-MOT supply, questions for Mike S.
Original poster: "Steve Lawson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <slawson-at-basec-dot-net>
Dear Mike:
Nice job with your 4- MOT powered TC. I admire your
engineering
layout of your PC boards too. I have a few questions I wondered if you
could answer.
1. In your website your mention that you're using 2 MOT's on the
primary
side for ballasting. First, do thy heat up sufficiently to warrant
submerging them in oil?
[Michael Strube] The MOT ballasts are not submerged. In the picture on
the website, they are sitting exposed on the top of the cart. I started
by using both connected in series but finally just opted for one. On
extended runs over 20 minutes, it gets warm but not hot.
Secondly, are you using any PFC caps wired in
parallel with the 2 MOT's which I'm assuming are in series with their
secondaries shorted? (correct me if I'm wrong).
[Michael Strube] Yes, the single MOT ballast that I am using has its
secondary shorted and is in series. I found by experimenting with PFC
ranging from 0-420 uF that 140uF produced the best result. That PFC is
wired in parallel ahead of the MOT ballast.
2. Your website also says that you're using 51uF MOT caps per secondary
leg
for secondary side ballasting. I'm confused about this rather large
capacitance because most MOT caps are approximately 1 uF with a 2000
volt
rating. How many caps are you using and how are they wired together;
Series or Parallel within each leg?
[Michael Strube] Poor use of spacing and wording on my part when I
listed that. Each secondary leg has five individual 1uF MOT caps that
can be jumpered in a variety of ways. I use two of the 1uF caps in
series per leg. That produces terrific output and keeps the current draw
tame.
Any input will be helpful in allowing our coiling group to
give
MOT'S a try in a safe manner too. It looks like you've taken all the
right
safety precautions while building your power supply.
[Michael Strube] I've been very very impressed with this supply. I've
run it hard night after night and it runs very reliably. Let me know if
I can offer any other advice. Best, Mike.
Sincerely,
Steve Lawson (Coiling in South Dakota)
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, December 07, 2002 11:20 PM
Subject: 4-MOT supply---Oh, my, my
> Original poster: "Michael Strube by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <mjstrube-at-earthlink-dot-net>
>
> Hi Folks,
>
> At the end of last summer, my first light experience came to an
abrupt
> end with the demise of my 12/60 NST. Having heard so many
endorsements
> for MOT based supplies, especially their hardiness, I decided to give
> that a try. I recently completed construction of a 4-MOT supply and
> fired it up for the first time this week. You can plant me right on
top
> of that MOT bandwagon. The results (using 81.8nF MMC, 3.875 primary
> turns, trigger gap, and some ballasting---see full details at
> http://home.earthlink-dot-net/~mjstrube/tesla.html) were spectacular. I
> routinely run this thing for 15-20 minutes continuously (wearing a
mask
> to hold off the ozone) with great performance throughout. I have to
keep
> the input to about 90 V or so or the streamers hit the ceiling too
> often. Should be fun to fire it up outside at full tilt. This thing
has
> far outstripped the expectations I had. My remaining NST will surely
be
> gathering some dust. I've taken a few pictures of the construction of
> the supply as well as some pictures of the coil in action using the
> supply. They appear on the website.
>
> Cheers,
>
> Mike
>