[Prev][Next][Index][Thread]

NEW POLE TRANSFORMER

 * Original msg to: Esondrmn-at-aol-dot-com

Quoting Ed Sonderman:

 ES> Richard,

 ES> I picked up my transformer today from local utility company. 
 ES> It says on the nameplate: 14400/24940  120/240  5KVA.  It is 
 ES> made by Westinghouse and was tested by the utility company.  
 ES> It is a two bushing transformer.  With three low voltage     
 ES> lugs all isolated from the case. 

Sounds like the cat meowed!

 ES> I am confused by the label. I thought a 14400 was 14400v in  
 ES> and 240/120 out. What is the meaning of the 24940 number?

When in doubt, always meter it out. Connect the hot terminals
from a neon sign transformer across the two high voltage
bushings. It has been my experience that this is the easiest way
to rough test winding ratios and continuity. On a 5 - 15 kVA pole
pig the output from a 30ma neon is sufficient to energize the
core for testing. On the higher kVA rated transformers I find
that 60 - 90 ma of HV current is required to energize enough to
get a VOM to read reliably.

Anyway, once you get your neon's HV outputs connected across the
high-voltage bushings of the pole pig, put your meter across the 
low voltage bushings and take some measurements. This will give
you a rough idea of the turns ratio.

The pigs that I have show the internal wiring diagram on the
plate. But you can also check that there is no continuity between
the high-voltage windings and the case with your Ohm meter. While
you are at it, you can measure the Ohms resistance on a working
neon (both primary & secondary) and compare that to the primary
and secondary windings on the pole pig. If you do this, then you
will be thoroughly convinced that you are dealing with a
different breed of power supply.  

 ES> I paid $100.00 for this transformer - a good deal I think.   
 ES> I have spent that much already on neon sign transformers.

$100.00 is an excellent price for the pig.

 ES> If I remember correctly, you said to leave the center of the 
 ES> safety spark gap connected to main RF ground and to          
 ES> disconnect the ground from the two filter caps so I just     
 ES> have the two filter caps in series with each other and       
 ES> connected across the high voltage outputs from the trans-    
 ES> former.  And also to ground the case of the transformer to   
 ES> the main RF ground.  Do I have this correct?

Yup.

 ES> Now that I have a good power supply, and my commercial       
 ES> capacitor should be here in about 4 weeks - can I damage my  
 ES> coil by applying too much power? 

Anything is possible, and failures will occur even in rated
equipment. 

 ES> Let's talk spark gaps.  So far, I have only been using one   
 ES> cylindrical spark gap (I have two) with seven 2.0" dia       
 ES> copper electrodes in it. It has a 100 cfm fan and the gaps   
 ES> are about .030".  It fires with the variac at about 40 or    
 ES> 50% using a 12kv 120ma power supply.  I think I will need to 
 ES> use both spark gaps in series but my experience says they
 ES> will not fire until I get up to about 80% on the variacs -   
 ES> and I want them to fire much earlier.  

Place the two gaps units in parallel.

 ES> Do I need to start thinking about a rotary gap?  

This is the point where nearly every coil is forced to begin
using rotary gaps. 

 ES> Does anyone have any plans?  

I do not have plans.

 ES> Is it important to use a constant speed motor? 

I have seen more wild 'n' crazy rotary gap units than you can
shake a stick at. Fixed speed synchronous, fixed speed non-
synchronous, and variable speed. Every type works, some
particular designs are better, some worse, but they all work.

Bill Wysock swears by synchronous rotary gaps that run at a fixed
speed and are set up to fire at specific locations on the input
supply waveform.

The Tesla Museum in Colorado Springs had a Black & Decker grinder
with one grinding wheel removed. The wheel was replaced by a
sheet metal disk that had holes drilled and tapped around the
circumference. The tapped holes had #10 (or possibly 1/4 inch)
long brass machine screws threaded through the holes, so that the
screw shafts protruded enough to be used as rotating electrodes.
It worked, but as I was looking at the jury-rigged contraption
the museum guy energized the coil and I was pelted with molten
brass and red hot dross as the soft brass electrodes burned and
melted in the hot arc.

Sid Romero out of Salt Lake City uses a similar method, but he
uses a larger fixed speed motor mounted on heavy 1" marine grade
plywood, and everything is bolted down with carriage bolts. He
mounts a pulley on the motor shaft and belt drives the power to
the rotary disk mounted about a foot away. This prevents HV from
getting into the motor. He uses a heavy steel disk about 3/8 of
an inch thick with a shaft through the middle that runs on three
sets of sealed roller bearings. The outside of the disk is
drilled and tapped for 3/8 inch long steel bolts. The steel bolts
are threaded through the rotating disk so that they extend out
far enough to be used as moving electrodes. He then caps the ends
of the 3/8" steel bolt shafts with chrome plated, hardened steel
acorn cap nuts. When the cap nuts become eroded, the are simply
unscrewed and replaced.

Richard Hull has developed some outstanding rotarys and is a firm
believer in extremely high break rates for Magnifier operation,
and variable break rates in 1/4 wave coils. He uses a large DC
series wound motor with a variac controller. The variac output
runs through a full wave bridge rectifier.  

Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12