DIYbanter - View Single Post - problem with triacs with neon transformer loads

Winfield Hill wrote:
wrote...

I am designed a commercial neon lamp two channel flasher and connected
to my hotels name board. The circuit is having two parts, one is
flashing circuit and the other is the output stage, wher the phase
line is switched. In the out put stage i have used BTA 41 triacs for
switching the neon transformer, ie the phase to the transformer is
connected through the triac. The gate signal is controlled through one
MOC3083 opto triac. the output from the flashing circuit is connected
to the opto triac's(MOC3083) input (LED).

The problem with switching transformer primaries with triacs is
the high inrush current that can develop. For example, if the
transformer magnetizing flux is strongly of one polarity when
it's turned off, and the ac line is pushing toward the peak of
the other polarity when the triac is turned on, the transformer
core will saturate and the primary will look like a section of
thick copper wire across the AC line. Very high currents will
flow for a portion of an ac cycle. Your triac is designed to
handle a little of this, but it's highly stressful and should
be minimized.

There are several solutions, including zero-crossing switching,
or a two-stage switch with a series resistor in the first path,
or both.

Haha- write more- Genome is having too much fun here-)