triggered gap, "theory and operation"
(click on pics for link to full size)
i have been asked to set up a page that explains the construction, operation and the "WHY'S" of the triggered gap, so i'll do my best here.
the basic idea of the triggered gap in syncronous operation to the line voltage, being 60hz or 50hz, is that the light dimmer unit holds off the flow of current until a variably set voltage level
as you can see the wave form is pulsed on at different points, this pulse is then used to energize the primary of a suitable hv coil. i use a ford ignition coil, but i would think that any ignition or pulse coil could be used?
i use the ford because of it's ease of conecting and the simple atatchment of a high voltage lead.
the 120vac from the wall feeds through the dimmer unit, into a 12 microfarad capacitor for limiting the current drawn by the coil, then into the + (or bat) terminal of the coil. the neutral is carried right to the - or neg. terminal of the coil.. the hv lead is brought out of the coil and conected to the triggering electrode, this triggering electrode is placed inbetween the two main gap electrodes at a slightly "off center" axis.the theory of operation is that as the main tank capacitor is charged by the main transformer, the wider gap spacing that is allowed by the triggered gap holds off arc over of the gap. then when the dimmers tric is fired and energizes the primary of the trigger transformer a high voltage pulse is sent to the trigger electrode causing an arc from it to one of the main electrodes. this small amount of arcing is enough to cause the main gap electrodes to arc, or conduct the flow of current from the main tank capacitor.
there is much more technical explanations, but i think this will suffice.
when the main gap arcs the current in the tank passes into the primary, at the same time the dimmers triac has shut down because the line wave form is passing the zero crossing point. the main gap continues to conduct until enough energy has passed into the primary and oscilated into the secondary to drop the capacitors charge low enough to not be able to continue conduction, at this point the gap shuts down.
as the lines wave form swings into the oposite polarity it starts charging the main tank capacitor again and at the point where the triac turns on, the gap arcs and discharges the tank again, this repeats until power is shut down.
a pic supplied by ted rosenberg, thanks ted
