A
TRIAC is used in AC power control applications in order to switch high
voltages and high levels of current over both parts of the AC
waveform. As a result, triac circuits are used in a number of
applications that require power switching. The triac was developed after
the creation of the thyristor which is able to control AC current over
one half of the cycle. The triac circuit can be visualized as two
thyristors that are opposite, parallel, and have the two gates connected
together with the anode of one device connected to the cathode of the
other. A common household device which uses the triac circuit are light
dimmers found in domestic houses
TRIAC Composition
The
basic Triac circuit has bi-directional properties. Similar to a
thyristor, it has three terminals with a gate acting as a trigger to
turn the device on. The other two terminals are then referred to as Main
Terminal 1 (MT1) and Main Terminal 2 which have similar properites due
to the bi-directional nature of the circuit
How Does a TRIAC Work
A
TRIAC is triggered by a positive or negative voltage being applied to
its gate electrode. Once the circuit is triggered, it will conduct
elecgtricity until the current drops below the designed threshold value.
As a result, they permit the control of large power flows with very
small control currents. TRIACs also let the percentage of current that
flows through the circuit to the load to be controlled which is also
referrred to as phase control. TRIACs will normally have a DIAC included
in the circuit when used as a control for electrical equipment in
order to dampen the level of harmonics produced by the circuit
What are the Uses for a TRIAC
There
are a number of uses for TRIACs in industry in small AC power
applications. Examples of uses of TRIACs include dimmer switches, speed
controls for electric fans, in computerized control circuits of
household appliances, and in electric motor controls
