triac .pptx

power electronics
topics ( TRIAC)

1. TRIAC Triode for alternating current

2. INTRODUCTION Triac is a three-terminal semiconductor device that is used for controlling the flow of current. It is commonly used in AC power control applications. A triac can switch AC power to a load in either direction. It consists of two thyristors connected in parallel, with the gate of one connected to the main terminal of the other.

3. Triac Symbol 3

4. Construction of triac Two SCRs are connected in inverse parallel with gate terminal as common. Gate terminals is connected to both the N and P regions. It consists of three terminals: main terminal 1(MT 1 ), main terminal 2(MT 2 ), and gate terminal G. 4

5. 5 Working There are four different modes of operations, they are- MT2 is positive with respect to MT1 with a gate polarity positive with respect to MT1. MT2 is positive with respect to MT1 with a gate polarity negative with respect to MT1. MT2 is negative with respect to MT1 with a gate polarity negative with respect to MT1. MT2 is negative with respect to MT1 with a gate polarity positive with respect to MT1

6. VI characteristics of TRIAC 6

7. 7 Advantage It can be triggered with positive or negative polarity of gate pulses. It requires only a single heat sink of slightly larger size, whereas for SCR, two heat sinks should be required of smaller size. It requires single fuse for protection. A safe breakdown in either direction is possible but for SCR protection should be given with parallel diode.

8. Use of triac They are used in control circuits. It is used in High power lamp switching. It is used in AC power control.

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