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Re: Neon life (and death) -> protection networks




From: 	Gary Lau  30-Oct-1997 1609[SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: 	Thursday, October 30, 1997 2:15 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Neon life (and death) -> protection networks

From:	HDECAD::LAU          "Gary Lau" 30-OCT-1997 16:08:03.50
To:	US8RMC::"tesla-at-pupman-dot-com"
CC:	LAU
Subj:	Re: Neon life (and death)

I'm not sure I see the protective value in having just chokes and/or
resistors in series with the xfmr outputs, without also employing bypass
caps to ground.  When one has a choke in series PLUS a cap from the xfrm
output to ground, this forms a two pole low pass filter.  If one has only
the choke in series, what does that accomplish?  The transformer
secondary inductance has got to be orders of magnitude higher than most
chokes used.  Assuming the HF induced voltage is divided evenly across
the total choke-plus-secondary inductance, won't the portion dropped
across a choke-only network be not enough to be worthwhile?

On the topic of resistors, I have 3K 50W units in series with my
15KV/30mA transformer (along with chokes and caps).  I figured W=I*I*R or
only 2.7 Watts, but you don't want to touch them after running for a
minute!  Could 60 Hz resonant operation be pulling THAT much more
current?  I must be calculating something wrong.  While the resistance
may be somewhat high (I'd normally shoot for 1-2K), it looks like the
Wattage needs to be higher.

Regards,
Gary Lau
Waltham, MA

================================================================================

>From: 	DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
>Sent: 	Wednesday, October 29, 1997 9:57 PM
>To: 	Tesla List
>Subject: 	Re: Neon life (and death)
>
>to: Greg
>
>Try an air-core choke in series with a 1K, 25 watt resistor.  Digi-Key has
>them (vitreous enamel) in 25, 50, and 100 watt ratings.  Calculate the
>voltage drop across the resistor x the average current thru it to determine
>the wattage ratings.  We have used some 2K 100 watt units in parallel to
>operate with pole pigs at 5 kva.  For higher powers we use some iconel
>resistance wire to wind our own 20 Ohm, 10 KW resistors.  It usually only
>takes 10 to 100 Ohms of resistance to "spoil the Q factor" enough to dampen
>any high potential transients of high freq nature.  
>
>Hope this helps out.
>
>DR.RESONANCE-at-next-wave-dot-net
>

>----------
>> From: Tesla List <tesla-at-pupman-dot-com>
>> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
>> Subject: Re: Neon life (and death)
>> Date: Wednesday,October 29,1997 7:18 PM
>> 
>> 
>> From: 	ghunter-at-mail.enterprise-dot-net[SMTP:ghunter-at-mail.enterprise-dot-net]
>> Sent: 	Wednesday, October 29, 1997 3:20 PM
>> To: 	tesla-at-pupman-dot-com
>> Subject: 	Neon life (and death)
>> 
>> What's the typical lifespan of a neon TC power supply?  One
>> subscriber to the list has suggested that a pile of used neon
>> transformers is good to have around, because they don't last very
>> long.  I find this most disturbing, as I own only ONE neon
>> transformer, and it wasn't free.  I've seen working luminous sign
>> transformers in downtown New Orleans that appear to have been on
>> continuous duty for decades.  Obviously, neons are built to last.  So
>> why would a TC shorten the life of a neon so drastically? I'm aware
>> of the need for output chokes, and mine will be protected with four
>> (4) robust, home-made units (2 big air-cores, and 2 fat ferrite
>> cores).  I'm also including a safety gap.  What more can I do? 
>> Series power resistors maybe?
>> 
>> Greg