TRIAC

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