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Re: Lt bulb for pwr resistor?




From: 	Gary Lau[SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: 	Friday, September 05, 1997 7:36 AM
To: 	tesla-at-pupman-dot-com
Cc: 	lau-at-hdecad.ENET.dec-dot-com
Subject: 	Re: Lt bulb for pwr resistor?

>There's been some discussion recently of the need for heavy-duty
>power resistors as part of a network to protect neons from HF spikes.
>An ordinary light bulb is quite good at high-temperature operation,
>and its resistance at incandescent temperature is several times its
>cold resistance---a nonlinearity that I'd guess would be quite
>suitable for damping unwanted oscillations in our protective RFC-
>BPC circuit. Does anybody use bulbs this way and if not why not?

While I'm still trying to sort out all the details, I think a light bulb
would be unsuitable.  The standing recomendation is to have several K of
resistance.  At full power at 120V, a 40W bulb would be only 360 Ohms,
cold measures 25 Ohms.  With cold resistance that low, it would never
heat up.

Gary Lau
Waltham, MA