How are TRIACs used as a power controller?
This results in a controlled supply of power to the load. Triacs are popularly used as a solid-state replacement of relay for switching high power AC loads. However, there’s another very useful feature of triacs which allows them to be used as power controllers, for controlling a given load at a desired specific power levels.
How are TRIAC phase control circuits used in heaters?
A variable zero-set has been provided by changing the 47K resistor with a 100k potentiometer. The various Triac phase control circuits discussed until now may be applied to control heater type load applications, although the load temperature being controlled might change with variations in the input AC voltage and the surrounding temperature.
What is the nominal voltage of a TRIAC circuit?
Most of the practical circuits show two sets of component values for use with normal domestic/commercial 50Hz or 60Hz AC voltage supplies with nominal values of either 240V (as used in most of Europe) or (in parenthesis) 120V (as used in most of the USA).
How is the TRIAC triggered in an isolated circuit?
Q2 is driven via the optocoupler from the isolated external circuit, and the triac is on when SW1 is open and off when SW1 is closed. FIGURE 12. Isolated-input AC power switch with DC triggering. Figures 11 and 12 show variations in which the triac is triggered via a transformer-derived DC supply and a transistor-aided switch.
What happens to the TRIAC when the lamp is closed?
When SW1 is open, the triac acts as an open switch and the lamp passes zero current. When SW1 is closed, the triac is gated on via R1 and self-latches shortly after the start of each half-cycle, thus switching full power to the lamp load.
How long does a TRIAC phase control circuit last?
Triac to conduct only for a very short time while the AC waveform travels across its end of the half cycle. Although the dimmer circuit demonstrated above really is easy and low-cost to construct includes one significant limitation – it doesn’t allow a smooth control of power on the load from zero to maximum.