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Re: AC Resistance (formerly Spice Simula
Could you share the data in realtime as you collect it
via spreadsheet maybe??
Barry
----------
|From: "tesla-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|To: Benson Barry; "Tesla-list-subscribers-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|Subject: Re: AC Resistance (formerly Spice Simula
|Date: Friday, November 01, 1996 3:28AM
|
|<<File Attachment: 00000000.TXT>>
|From lod-at-pacbell-dot-netThu Oct 31 22:39:48 1996
|Date: Tue, 31 Oct 1995 12:04:31 +0000
|From: GE Leyh <lod-at-pacbell-dot-net>
|To: tesla-at-pupman-dot-com
|Subject: Re: AC Resistance (formerly Spice Simulation Pictures)
|
|Bert Hickman wrote:
|
|<snip>
|>
|> Secondary Parameters:
|> Diameter: 10.25 inches
|> Coil active Length: 31 inches
|> Wire Gauge: #21 AWG Double Formvar
|> Wire (Cu) diameter: 0.0285 inches
|> Wire (Cu) diameter: 0.072 cm
|> Fo with Toroid: 91 kHz
|> DC Resistance: 34.1 Ohms
|> Inductance: 73,455 uH
|> ZL at Fo 42,000 Ohms
|> Est Turns: 995 (97% close-wound)
|> Est Turn:Turn Spacing: 0.0312 inches
|>
|> 1. Measured/calculated Value of Rac:
|> My estimate for Rac was done by backfiguring from the time constant of
|> the decaying exponential secondary voltage captured on a storage scope.
|> You could also base-excite the secondary/toroid from a low impedance
|> variable-frequency source, measure frequencies at the 0.707 points,
|> calculate Q, and then back-figure Rac.
|>
|> Conditions: gaps reduced for no corona breakout, gaps quenched at
|> end of 1st beat, "single shot" mode, with a pickup plate 7' from
|> secondary and connected to a storage scope.
|>
|> The time for the output waveform to to go from the peak voltage to 5% of
|> peak was about 2 milliseconds. This equates to 3 time-constants (3*Tau)
|> for the exponential envelope, so Tau = 670 uSec. But, Tau = 2L/Rtotal,
|> where Rtotal = Rac + Rground. I estimated my RF ground resistance to be
|> about 15 ohms based on low-voltage AC (6.3 VAC) current measurements
|> from the dedicated RF ground to AC (line) ground. Solving for Rac:
|>
|> Rac = (2L/Tau) - Rground = 110 - 15 Ohms
|> Rac = 95 Ohms
|>
|> 2. Purely calculated method for a close-wound coil (from Frederick
|> Terman, Radio Engineers' Handbook, 1943, McGraw-Hill, pp.77-80):
|>
|> Rac/Rdc = aH + (bu1 + eu2)G[(d/c)^2]
|>
|> Variables H, a, b, e, u1, u2, and G are all derived from the coil's
|> parameters, operating frequency, and a number of look-up tables. Term aH
|> is the skin effect contribution, and the remaining term is from
|> proximity effect. Solving for the above conditions yields the following:
|>
|> Rac/Rdc = 1.263 + 1.160 = 2.423 (combined effect)
|> (skin) (Proximity)
|>
|> Rac = 2.423*34.1 = 82.6 Ohms
|>
|> Considering my measurement errors (especially in estimating Tau and
|> ground
|> resistance), the two values are in reasonably close agreement. BTW, the
|> first method is _much_ simpler than several calculations and
|> interpolations from multiple tables!
|>
|> Given the above parameters, what does your graph predict for Rac?
|>
|> Safe computin' to ya, Jack!
|>
|> -- Bert --
|
|
|Nice analysis, Bert! I am curious as to how the streamers appear on your
|coil,
|do you have any pictures posted of it in operation? Have you noticed any
|peculiarities in how the streamers grow, or move about? Also, have you by
|chance measured the wall-plug power of your coil at a given arc length?
|
|I have been collecting data on all types and sorts of coils, and your
region
|of
|parameter space is still sparsely populated (ZL at Fo = 42000 Ohms).
|
|Quantitative coilin' to ya, Bert!
|
|-GL
|