Re: GETTING CLOSER!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-uswest-dot-net>" <broker-at-uwplatt.edu>

Last weekend, I ran my 15/90 coil for about 90 minutes with a duty cycle of
about 50% (taking LOTS of pictures).  That is to say that it ran for roughly 45
minutes.  When properly tuned (amazing how much changing the SRSG dwell time by
+-.5ms will make), I draw about 17A through my 10A variac.  By the end of the
evening, it was slightly warm (say 15deg F above ambient).  I must have popped
about 15+ 20amp fuses (including the 4 or 5 when I had to use it with a a
friend's 12/180 system when his control board fried....).  It takes a little
while for the large mass of iron to heat up too far....

Coiling for the budget conscious means pushing ratings.  It would appear that
in general, ratings are about 1/2 their "true" rating, esp when only running
for 5 minutes at a time with < 50% duty cycle.

Mark B.

<snip> 

>
> I will only be running one
> tranny off the variac at a time (at first).  I have the variac over fused on
> a recommendation I received off the list from a fellow coiler who, like
> myself, has an interest in getting as much power out of things as possible.
> I like having a small variac and the ability to give my tranny a boost for
> short runs. Its power output rating is 543.75 W.  I figure one NST will draw
> 360 W.  No problem with that set up, the ten amp fuse is for when I will
> inevitably go for the two NST's in parallel.  I have the equipment to run my
> coil with 4 different configurations.  Although I haven't done any of them,
> this is my plan.
> 1) Single tranny no boost
> 2) Single tranny with variac boost
> 3) Dual matched paralled tranneys no boost
> 4) Dual matched paralled tranneys with variac boost
> For the final configuration, I am only squeezing!
>  an additional 176.25 W out
> of my variac.  I have been advised that I should be able to fuse it at 10
> amps for short runs.  Having read your reply I think I will change my fuse
> rating to 3 amps (435 W) on configuration 2, and 5 amps (725W) for
> configuration 4.

<snip>


>
>>
>> 2. Your Variac is rated for ~ 550 W power, your two trannies will draw at
>> least 720 W.
>> How do you plan to cool your Variac?
>> 3. With a 10 amp fuse protecting a 3.75amp Variac, won't the Variac smoke
>
> to 
>>
>> protect the fuse?  I have 15-Amp fuse protection on a 20-Amp rated Variac 
>
> to 
>>
>> an NST that should only draw 8.35Amps Max, but where I live fuses are much
>> cheaper than Variacs. 
>