Re: Computer data

From: 	Greg Leyh[SMTP:lod-at-pacbell-dot-net]
Sent: 	Sunday, August 31, 1997 2:41 PM
To: 	Tesla List
Subject: 	Re: Computer data


> Even without CW the tank current will dip as noted on the primary side
> ammeters.  We did this experiment in Calif. in 1981 with Bill Wysock
> running one of
> his large coils -- I believe it was a model 10.  The coil output was around
> 32 ft. long spark.  

Bill certainly has an unusual way of rating the performance of his coils. He
may be stretching things a bit to derive a 32 ft. arc length, at least from 
the pictures shown in http://www.ocws-dot-com/tesla/model10.html.  
It appears that he measures the peak _diameter_ of the arc striking range, 
rather than the actual arc length.  This could explain the 55 ft. claims made
in the second photo at http://www.ocws-dot-com/tesla/model13.html.  Tesla also used 
this peak diameter measurement method at one point to measure the performance of 
his Colorado Springs expmt, where he describes the arcs as being "50 ft across."

> The power supply was set up with a continuously
> variable series inductor and a standard parallel variac stack.  As we ran
> the power up thru the voltage variac in small increments we made small
> adjustments to the series inductor.  At almost any setting above 50% power
> level (the range we are most interested in) as one increased the variac
> (voltage) the current would begin increasing as well.  At some point as the
> power factor begins to correct back to unity (phase meter across input
> line) the primary 240 vac side of the power supply will indicate a 5-10%
> drop in the primary current to the power transformer.  This is what I refer
> to as the most efficient point of operation.  The current actually "dips"
> just like a plate milliammeter in a ham radio transmitter.  It's not as
> dramatic, but the effect is quite evident.  From this point the voltage
> variac is increased more and the primary current once again begins to climb.  

I understand now what you mean by dipping the input current, by tuning the 
effective _power factor_ of your system, not it's resonant frequency. 
I think that yours is the first attempt I've heard of to tune for optimum
power factor!  That is definitely a good capability to have, especially if you
are operating near the kVA limit of your feeder!

> I might
> suggest you incorporate several taps into your limiting inductor system and
> you will be able to "tune" your power supply as well as your resonance
> points.  A continuously variable inductor demonstrates these principles in
> dramatic effect but this would be a lot of work to construct for your very
> large system.  A phase shift indicator illustrating where unity is while
> your system is running is a very valuable addition to your instrumentation.

Unfortunately the PF is not adjustable on my setup, as the HV power xfmrs are
switched directly onto the 480V mains without the use of variacs or limiting
inductors (power is controlled by rotary gap speed).  However, on a DC resonant
charger the PF is usually well above 0.9, since the inductive reactance of the
charging inductor exactly cancels the capacitive reactance of the primary
capacitor bank as seen by the HV xfmrs.

> Regarding the data I posted .... does it agree with any of your measured
> values of current input vs spark length output for your old system with the
> 0.18 MFD capacitor???

I cannot say for sure, since I measured my mains current at 480V 3-phase.
However, if I assume that your mains current values are for 240V 1-phase, then

Your prediction - at  90 amps input (21.6kVA)   x = 21 ft. long sec. spark
                  at 108 amps input (25.9kVA)   x = 25.2 ft. long sec. spark
                  at 130 amps input (31.2kVA)   x = 30.3 ft. long sec. spark

Observed (Bert Pool's Austin pics) at about 21kVA  x = 20(avg) to 25(rare) ft.
I would say that your data is in good agreement, for at least this one data point.