Hi
Look for SGS-Thomson application note "Control by a triac for an inductiv
load"
You will find the solution in using an alternistor instead of a triac for
this purpose.
Schematics included alternistor = TPDV 640 .... 1240
Ton Visch


wrote:

wrote:
Hi,
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).
I have installed the flasher in my hotel's neon name board. there is
two transformers connected to one flasher channel. it was working for
the last 4 months. last week one channel was not flashing. only one
channel is flashing the other channel is in ON state, ie not blinking.
The next when i checked the flasher in my lab both of the channels was
flashing. again i connected the flasher to the same neon board. After
two weeks agin the same problem occured, ie one channel was not
flashing. Can anbody know the reason for that. Is that problem with
Opto triac(MOC3083) or BTA 41. Is there any possibility of humidity or
temparature cause the problem

Thanks in advance

Raseel.M

Firstly as has been mentioned switch on at the AC maximum to reduce the
inrush. Triacs are not good for this application since they go off at
the current zero crossing point which is when the voltage is near
maximum. This sudden application can cause the triac to conduct during
the current "off" time so when the current tries to reverse you get
conduction once again. Large snubbers can help out but its marginal at
best, this is why sometimes it works and sometimes doesnt. The solution
is to chuck out the triac and use two thyristors instead.