Re: Filament voltages

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

Tesla list wrote:

> Original poster: "rheidlebaugh by way of Terry Fritz

><twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>
 
> Dave: Am I reading correctly, 4 tubes with 10V 10 A filament.

> If so that is 10V 40 Amps or 400 watt.  I would not use under

>#10 wire to avoid wire heating.


	Concur, more or less.  I was addressing the '10A'
	only.  If 40A, then something heavier may be
	in order.  Still, for short runs...  Or use
	4 SETS of #10, one for each tube.  Likely good
	to go heavier on the WINDING (if it will fit...  And if
	it WON'T fit, then THAT is a problem).

	Mention was made of I**2R losses:
	Taking 40A (total) indeed one gets 1600 for I**2.
	R for #10 is roughly 1 ohm per THOUSAND feet.
	From this the loss in a hypothetical winding and
	hookup wiring can be had.  Guessing:
		10 feet of winding: 0.01 ohms
		*40 ==0.4V drop at full load, from winding.
	Allow another 10 feet for hook up, another 0.4V.


	Losses for this _ASSUMED_ case would be:
		1600 * 0.02 =32 W
	Nontrivial, survivable.

	Drop from no load to full load can be due to:
		Winding R
		Hookup R
		Core limits.
	(And i may be forgetting summat...)

	best
	dwp