Jim,

re: bulb start up current

typically 10X steady state depending upon line impedance -- duration 20-30
cycles
series resistance reduces this

big problem with triac and SCR control is flashover at end-of-life -- there
is no longer a current limit of the cold resistance of the filament -- the
current is limited only by the line impedance (and the bond wires - if any -
in the triac/SCR) - so its possible to have flashover currents exceeding 100
A

when flashover occurs a plasma is created (the filament is now 0 ohms) --
normally the plasma would extinguish at zero crossing but if the metal
around the filament stays shorted thru the zero crossing it may continue for
for 100 msec until the field is too weak to overcome the gap at a zero
crossing...

the flashover current is not related to the bulb wattage but the
construction of the filament and the supports -- example 7 watt 7S7 bulbs
have more of a flashover problem than 150 watt spotlights..

Ken

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads