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RE: The PING Test
Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
Malcolm -
One way of looking at this result is to consider the overall efficiency
which would then be
OAE = 400 x 100/(300 x 8) = 16.67%
But how did you get the Q of 300? I have not as yet found Q's that high. Did
you use the Ping test? What were the parameters of the secondary coil?
John Couture
-----------------------------
-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, September 24, 2002 6:58 AM
To: tesla-at-pupman-dot-com
Subject: RE: The PING Test
Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<m.j.watts-at-massey.ac.nz>
Hi John,
What voltage should I expect with a primary voltage of 8kV
and a Q of 300? Problem is, Vs = Vp*Q applies *only* to a CW driven
system. According to COE physics and single shot tests, 400kV is
about what the above system actually does get.
Regards,
Malcolm
On 23 Sep 2002, at 22:29, Tesla list wrote:
> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
>
>
> The Ping Test is the most fundamental of all Tesla coil tests. The TC
> operates using a dampened wave and the Ping test also uses a dampened wave
> unlike other tests. A robust pulse generator is needed for good results. I
> used a HP 214A which can produce pulses of 100 volts into a 50 ohm load.
> These pulse generators are still available on the surplus market at
> resonable prices.
>
> In the Ping test the TC secondary coil is pinged with a pulse from the
> generator and the ring down of the dampened wave noted on a standard
> oscilloscope. The test setup is very simple and a storage or digital scope
> is not necessary because the pings are repetitive. The decrement or
> decreasing of the waveform can then be used to give the TC researcher
> important information regarding how his TC system will perform.
>
> A crucial and difficult to determine TC parameter of the secondary coil is
> the Q factor of the coil. The Q factor can be used to estimate the
secondary
> voltage of the TC. The equation is
> Vs = Q x Vp where Vs = secondary voltage
> Vp = primary voltage
>
> The Q factor can also be found by the equation
> Q = 6.283 F L/R where F is the frequency,
> L is the inductance of the secondary and R is the resistance.
> The problem with this equation is that both Q and R are unknowns. However,
> if we can find the Q factor with the Ping test we can then find the R
> parameter.
>
> In order to illustrate how the Ping test can be used to determine the Q
> factor I tested a 4" x 15" secondary coil with 1000 turns of #28AWG. The
> coil inductance was 30.6 mh and the frequency was 91.84 KHz. When the coil
> was pinged the scope showed the dampened waveform decreased to 10% in 27
> cycles. This gave a Q factor of
> Q = pi/log dec = 3.1416/(ln(10))
> Q = 1.364 x cycles = 1.3644 x 27
> Q = 36.82
>
> If the TC primary voltage is 15 KV the estimated secondary TC voltage
would
> be
> Vs = Vp x 1.4 x Q x eff
> Vs = 15 x 1.4 x 36.82 x .50
> Vs = 386.61 KV
> with an overall efficiency of 50%. The efficiency would vary depending on
> the quality of construction, the wire insulation, etc. The overall
> efficiency can be found with the lamp tests mentioned in earlier posts.
>
> To find the effective resistance "R" when the coil is in operation and
35.47
> is the Q factor.
> R = 6.283 x F x L/Q
> R = 6.283 x 91840 x 0.0306/36.82
> R = 479.55 ohms
> The DC resistance of the coil was 76.9 ohms. The effective AC/DC operating
> resistance ratio of the coil is
> AC/DC Ratio = 479.55/76.9 = 6.24
>
> This resistance ratio with the same H/D can be changed using less turns
and
> larger wire or more turns and smaller wire. Should the secondary turns be
> increased or decreased to increase the secondary voltage and the spark
> length with the same H/D coil?
>
> John Couture
>
> ---------------------------------
>
>
>
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