TRIAC Specifications and Recommendations (Turn‐On Behavior)
TRIAC is defined as an electronic component approximately equivalent to two silicon‐ controlled rectifiers (SCRs/thyristors) joined in inverse parallel (paralleled but with the polarity reversed) and with their gates connected together. This results in a bidirectional electronic switch which can conduct current in either direction when it is triggered (turned on) and thus doesn't have any polarity. It can be triggered by either a positive or a negative voltage being applied to its gate electrode.
Once triggered, the device continues to conduct until the current through it drops below a certain threshold value, the holding current, such as at the end of a half‐cycle of alternating current (AC) main power. This makes the TRIAC a very convenient switch for AC circuits, allowing the control of very large power flows with milliampere‐scale control currents. In addition, applying a trigger pulse at a controllable point in an AC cycle allows one to control the percentage of current that flows through the TRIAC to the load (phase control).