Power Electronics TRIAC - Power Electronics

What is TRIAC?

TRIAC (Triode for Alternating Current) is a semiconductor device which has three terminals for controlling the flow of current. In contrast to SCR, TRIAC is bi-directional and it is perfect for operation which makes use of AC power for switching purposes as it controls the current flow for both halves in an irregular current cycle. Below diagram clearly explains this scenario.


TRIAC Symbol

Below is the Circuit diagram for a TRIAC. It looks like two thyristors placed back to back.


TRIAC Structure

TRIAC Structure can be considered as a DIAC which has additional gate contact included to make sure the control of the device. Same like other power devices, TRIAC is also manufactured from silicon. As a result of this, the process of fabricating the silicon will be resulting in the manufacturing of less cost devices. As shown below, TRIAC will be having six areas known as four N-type regions and two P-type regions.


TRIAC Operation

TRIAC operation will be depending on thyristor and it helps the switching function in AC electrical components and systems. TRIAC operations are extensively used in light dimmers as they let both halves of the AC cycle to be utilized. This is the reason why it is making them more competent in power usage. Thyristors can be used to function as TRIAC, but turns out to be costly for operations which need less power. TRIAC can be viewed in terms of two thyristors.


TRIACs are generally used in applications which are not in need of high power consumption as they show non-symmetrical switching in their operation. This turns to be harmful for applications which use high power as it causes electromagnetic interference. Because of this TRIACs will be used in motor controls, light residential light dimmers and small electric fans to control speed.

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