Re: Cap Location (fwd) A correction (fwd)
---------- Forwarded message ----------
Date: Mon, 12 Jan 1998 22:30:46 -0700
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Cap Location (fwd) A correction
As John Couture probably suspected, I miss quoted the numbers for
resonant rise. With a 60mA 15KV neon transformer connected to a 0.01725uF
capacitor (no other load present), the resonant rise of the system raises
the output voltage by about 40% above what one would expect. Thus at 120
volts input, instead of 15KV on the output I may get about 21KV. This
stress usually will not kill a neon but doesn't help it much. The real
problem may be the input current. Spice modeling (which has accurately
predicted other parameters I have measured) predicts the input current to
the neon will be about 18A and the output current could go to 140mA.
Apparently, the neon's current limiting my no longer function as designed
when the output voltage and current are 90 degrees out of phase. This will
definitely hurt the neon if the theory is correct.
I have only tested this theory at low power due to current limits on
my equipment. Now that the probe is working, I can briefly push the system
to check this theory out. Since the transformer is brand new (former
testing did not go well :-(, I want to be very careful.
If anyone has any thoughts on neons drawing high currents or
producing higher than rated output voltages when a capacitor is connected to
their output terminals, I would be interest to hear them.
I haven't investigated power factor correction much but I fear the
power factor capacitor and the primary winding of the transformer may see
high resonant currents even though the AC input looks better.
Much to work on.......
>---------- Forwarded message ----------
>Date: Mon, 12 Jan 1998 19:44:01 +0000
>From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>To: Tesla List <tesla-at-pupman-dot-com>
>Subject: Re: Cap Location
>At 05:38 AM 1/12/98 +0000, you wrote:
>>Sent: Sunday, January 11, 1998 10:16 PM
>>To: Tesla List
>>Subject: Re: Cap Location
>> You must also be cautious of the output of the neon and the primary
>>capacitor resonating and producing higher voltages than you want. My 15KV
>>60mA neon and 0.01725uF primary cap can reach 15KV at only 40 volts AC in
>>due to this. If I were to put 120VAC into the neon it would hit about 45KV
>>and the cap or the neon would blow.
>> To make a long story short, go with the gap across the transformer
>>and use a good spark gap across the transformer to catch any induced spikes
>>during the break.
>> In a related note, my real-time fiber-optic voltage and current
>>probe is now working properly after many months of dealing with bandwidth,
>>noise, finding parts, etc. It can easily measure the situations we have
>>here. I have been trying it in a number of situations and I will soon have
>>it hooked to a full power primary circuit which will easily show the
>>differences between the two situations described above. I will report the
>>results as available. I will try the circuits without the secondary in
>>place for now since I have calculators, laptop, digital scope, etc. laying
>>all over the place. Not ready for any 4 foot arcs right now :-) I may need
>>to build a new spark gap first. According to the probe, my present gap
>>really sucks! Works for a few pulses then just acts like a continous short.
>>You can easily hear the transition from proper arcing to poor shorting once
>>you can see it on the scope as it is happening. Very interesting stuff!!
> Terry -
> We will all be waiting anxiously to hear how your research turns out.
> One note of caution on the rise in destructive voltages. There is a big
>difference in whether the voltage wave is a sine wave or a nanosecond pulse
>wave. The type of waveform (RMS or Peak or pulse width) should be indicated
>for the voltage. The sine wave requires much greater energy than the pulse
>type. A gain in sine wave voltage could require a gain in input energy. This
>is not true of pulse type waveforms. However, either waveform can destroy a
>transformer or other electrical equipment.
> What is the load on the neon with the 15 KV at 40 volts?
> John Couture