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Re: Cheap Variac Substitute?/ vs Expensive.




On Thu, 03 Feb 2000 08:26:57 -0700, Tesla List wrote:

>  Original Poster: Travis Tabbal <bigboss-at-xmission-dot-com> 
>  
>  Tesla List wrote:
>  
>  > I recently purchased 4  MONITOR ISO-V-AC III model WP 32 isolated power
>  > supplies that go to 150 volts-at- 10 Amps. These can function as variacs
as I
>  > can turn the voltage up from 0 to 150 with a dial.
>  
>  Not sure how those are built. There are some problems with the solid
state
>  devices being used for this when attempting to control a transformer. You
may
>  want to do a little more checking before hooking them up to a coil. I
wouldn't
>  want you to fry anything expensive. ;) At the least include a circuit
>  breaker or
>  fuse inline to prevent them from running away with you.
>  
>  
>  > I have several questions
>  > regarding operation. Do all variacs represent an isolated power supply?
Is
>  > there an advantage to using such a supply
>  > to a NST primary and does this consist of a means of protection against
RF
>  > kickback such that only a safety gap should then be needed
>  > as protection to NST damage on secondary?
>  
>  No. Variacs are autotransformers. There is no isolation when using them.
Nor is
>  there any protection for the NST in cases of kickback. Safety gaps and
other
>  means are required for that. To keep HF from getting into your power
lines you
>  should also use line filters on the input.
>  
>  
>  > Could I put all 4 in series to get
>  > 600 volts, or would there be any problems with having to simultaneously
turn
>  > up the voltage on each device?
>  
>  You would probably have to turn them all up and down at the same time to
>  prevent
>  them from fighting each other. When I wanted to parallel 2 variacs
someone
>  mentioned this problem to me. They sugested getting a 'paralleling choke'
to
>  make them be nice. Looks like a large center tapped inductor to me.
Although I
>  haven't verrified that. What would you run 600 volts into anyway? The
NSTs
>  wouldn't like that, you'd probably burn out the insulation on the
secondary.
>  
>  Travis
>  
The need for higher voltages is for a different large inductance high freq
device other than the typical design of tesla coils used for plant life
stimulation.(Bury a secondary ground in a garden row, operate coil for breif
periods daily)In about two weeks I am starting plots for pepper/tomatoe
greenhouse sales, and over the winter I have experimented with lower 120
volt household input on this device.
It produces a tingling sensation to finger touch on the plant life -at- 1700
volts about ground potential due the resonant rise of voltage on the large
induction coils. This device at higher voltages needs to be protected well
when driven by a transformer because its application is continuous
performance one hour/day. I have destroyed smaller 440kva transformers in
long term use in this manner and thought that using 4 of these ISO's  in
series would give the durable performance I need instead of relying a single
1.5 KVA 440 power transformer. The device could easily take 1000 volts input
so 600 volts seems like a ballpark figure.
Sincerely HDN


Binary Resonant System
http://www.insidetheweb-dot-com/mbs.cgi/mb124201





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