21 Feb
2011
21 Feb
'11
11:37 a.m.
On 21 Feb 2011 at 14:04, Shoppa, Tim wrote:
But... electronic ballasts are switching devices and
the current
is not steady-state. If twice the current flows for half the time,
then the power dissipation doubles (Remember, I-squared-R, you doubled
I, so I squared goes up by a factor of four.)
Let's do the math. Suppose the current went from 0.5A to 4A.
Probably, the 2A fuse in series with this thing would blow. If that
didn't happen, the resistor would be called on to dissipate about 5W--
on a transient basis, the resistor could handle this; on sustained
basis, the resistor would overhead and discolor and the PC board
would also be discolored. That didn't happen.
The resistor is a plain-Jane 2W light-brown painted body with orange-
orange-silver-gold markings. No letterings or other notations, no
discoloring--just two paint chips missing from the body.
I can post photos if you want.
--Chuck