TRIAC

TRIAC

     You can think of a triac as a three-terminal AC switch.

• It works differently from other silicon-controlled rectifiers because it can conduct in both directions, no matter what the applied gate signal is. This thing can be used as a switch in AC circuits because of this.
• This is an AC power controller with three terminals, four layers, and two directions. You can buy a triac with a maximum power of 16 kW on the market.

 Construction of TRIAC

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• Two SCRs are linked in inverse parallel, with the gate end acting as a link between them.
• The gate contacts are linked to both the N and P regions, which means that any gate signal can be applied, no matter what its polarity is. Because it works for both sides, there is no need for an anode and a cathode here. This means that the device is bidirectional.
• It has three terminals: gate terminal G, main terminal 1 (MT1), and main terminal 2 (MT2).

VI Characteristics of a Triac

It works with both positive and negative triac voltages, but the triac properties are like those of SCR.

 
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First Quadrant Operation of Triac

The voltage at MT2 is higher than the voltage at MT1, and the voltage at the gate is also higher than the voltage at the first end.

Second Quadrant Operation of Triac

The voltage at terminal 2 is higher than the voltage at terminal 1, and the voltage at the gate is lower than the voltage at terminal 1.

Third Quadrant Operation of Triac

The voltage at terminal 1 is higher than the voltage at terminal 2, and the voltage at the gate is lower.

Fourth Quadrant Operation of Triac

• The voltage at terminal 2 is less than the voltage at terminal 1, and the voltage at the gate is greater than zero.
• A current-regulating resistor should be connected to the outside of the device to limit the current that runs through it when it is turned on.
• If the current is too high, it could damage the device.
• The device's firing angle can be changed by using the right gate signal.
• For good gate triggering, the gate triggering circuits should be used. We can set off the gate pulse with a diac.
• For the right shooting angle, a gate pulse of up to 35 microseconds can be used to set off the device.

Advantages of Triac

1. The polarity of gate pulses can either be positive or negative to trigger them.
2.  It only needs one heat sink that is a little bigger than the SCR, which should have two smaller heat sinks.
3.  It needs a single switch to keep it safe.
4.  A safe breakdown can happen in either way, but a parallel diode should be used to protect the SCR.

Disadvantages of Triac

1. They are not very reliable compared to SCR
2. Its DV/DT grade is weaker than SCR's.
3. You can get scores that are lower than SCR.
4. We need to be careful with the wiring that sets off the alarm because it can go either way.

Uses of Triac

1. They are used in control circuits.
2. It's used to switch high-power lamps.
3. It is used to direct AC power.

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