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130kW Coil -- Oh No!




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From:  Wysock, William C. [SMTP:Wysock-at-courier8.aero-dot-org]
Sent:  Tuesday, February 03, 1998 8:46 AM
To:  Tesla List
Cc:  ttr
Subject:  RE: 130kW Coil -- Oh No!


Greg,

It sounds like you're really getting the (un-named) 130 KW
coil going now.  As for 5 amp full scale meters and current
transformers, yes, I've had considerable experience with
them (look at the pix of the Model 13M Magnifier 125 KW
power supply.)  There will be some new images of the
components used in that unit, posted in the next few days,
on my web site.

As for changing out the porcelain for G-10 stationary
electrode holders, you're right on!  I had to do the same
thing in my Model 13M magnifier (but in my case, I had
used linen based phenolic instead of porcelain; but
the phenolic got so hot that it bubbled, delaminated, and
oozed resin out of the material!)

All the C.T.'s and meters I used were either G-E or
Westinghouse switchboard components.  The problems
you had in accurate measurement of input a.c. current are
the same as I experienced.  I believe what is been seen
is out-of-phase currents, that give a higher current reading
then what is actually being consumed.  A Syncroscope
meter or a power factor meter will show this.  Another point
to note is that it makes a difference, where you are making
the current measurements in the circuit; i.e., an ammeter
in series right at the a.c. mains, another in series with the
primary of your H-V transformer, etc.  In my system, I measure
using three 400:5 C.T.'s and calibrated 8 1/2" d'Arsonval meter
movement ammeters reading 0-400 amps full scale.  Since
I use the double grouped and 6-ganged stacks of Variacs
to control input, I measure first at the a.c. mains (right after the
main 500 amp power breaker.)  Next, I measure after the first
6-ganged stack of W-50H Variacs (used for voltage control
as an actual autotransformer.)  Next, I measure after the series
connected 6-ganged stack of W-50 Variacs, used as a variable
series inductance.  I noted on all occasions, that the current
readings of the input, were more then shown after the voltage
control Variac stack, which was about only 70 % of what was
shown after the current limiting stack of W-50 Variacs.  Changing
the variable inductance, with the H-V transformer connected to
the 0.275 mfd. tank capacitors, but with the RSG not firing proved
to me, that I could make these current readings go all over the
place.  But always, when there was resonant rise in the power
circuitry (the condition that occurs when the Tesla tank circuit
is running and properly tuned for maximum smoke,) the load
ammeter would peg at over 400 A, the source ammeter would
read ~ 270 amps, and the line ammeter read about 280 amps.

If you take a 4 channel vertical input scope and monitor the
output of all your C.T.'s in their verious positions of the control
circuitry, and sync the time base to the input of the a.c. line,
you can see the phase shift changes in the different parts of
the circuit.  The C.T.'s don't "know" the difference between
forward going and reflected power.

Bill Wysock
 --------------------------------------------
Tesla Technology Research
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From: Tesla List
To: Tesla List
Subject: 130kW Coil -- Oh No!
Date: Tuesday, February 03, 1998 1:02AM


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From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent:  Sunday, February 01, 1998 4:47 PM
To:  Tesla List
Subject:  130kW Coil -- Oh No!

Hi All,

The final development and testing efforts of the coil during the
last few weeks have brought considerable progress, and a few setbacks
as well.  Most of the major problems so far have had to do with the
dynamics of the rotary gap system.

The latest setback on the rotary gap system has to do with
the sharp pulsations of air pressure exerted on the stationary
electrode holders by the quickly moving rotating electrodes.  As the
moving electrode passes the stationary one (at 420 km/h with a
clearance of 0.9mm), the shock wave tends to hammer the stationary
electrode supports, which are supported by an array of large porcelain
insulators.  These shockwaves are strong enough even at half speed
that hearing protection is required anywhere near the gap.
Although the porcelain insulators are quite massive, they appear to
be susceptable to vibrational fatigue, and during power tests
last Friday one of these insulators failed completely, resulting in
a rather impressive spray of porcelain shards, ejected out of the
vault through the access door.  T. Leonard was far enough away, and
I was behind my favorite steel plate, so no one caught any action.

On a positive note -- at the time of the insulator failure, the coil
was generating 22 ft long discharges into the air from the top sphere,
with the mains at one-fourth of full power!  Electrically speaking
at least, the coil appears to be doing quite well.
I finally got the Fluke ScopeMeter to work with the coil energized,
and grabbed some waveforms just before the rotary exploded.
The measured waveforms on the charging reactor and HV circuitry
have come out fairly close to the projected values from PSPICE,
with the exception that PSPICE predicted more ringing on the diode
stacks at the end of the charging cycle than was actually observed
with the HV scope probe. (those pesky ideal components)

* The charging reactor waveforms indicate that the coil is _not_
in fact drawing 2.5 times the normal amount of power (as the 60Hz
CT's on the mains indicate).  The current waveform measured on the
charging reactor is a haversine 4.8A tall by 3msec long.  PSPICE
predicted a haversine 4.6A tall by 2.4msec long.  With a HVDC of
12,700V and a rep rate of 200PPS, this gives a power usage of 32kW,
where the CT's on the mains say 120A per 400V leg!

Does anyone have experience with standard 5A FS panel meters and
300:5 CT's?  How sensitive are they to non-sinusoidal waveforms?

Also, we were able to bring the primary voltage to 55kV in the
single-shot mode (~1PPS), at which point the top sphere issues
7' to 8' streamers, and the RF current at the base of the coil
is 60A pk.

Our plan for the electrode support insulators involves replacing
all 8 of the porcelain posts with 3.5" x 6" x 27" solid slabs of G-10.
The material is already in hand; however the machining efforts,
modifications to the rotary gap frame and testing will probably
set our schedule back another two weeks.

I'll report on our progress again when the G-10 is installed.


 -GL