28 Triacs | Power Electronics

The video tutorial discusses the operation and applications of thyristors and TRIACs. It explains how TRIACs can control current in both directions, making them useful in devices like lamp dimmers and home appliances. The tutorial covers the construction of TRIACs, their terminals, and how they are triggered. It also provides examples to illustrate the concepts of delay and conduction angles, and how to analyze circuits to determine trigger angles.

What is the primary function of a TRIAC in electrical circuits?

• To convert AC to DC

• To control current in both directions

• To amplify signals

• To control current in one direction

Which terminals are present in a TRIAC?

• MT1, MT2, and Gate

• Emitter and Collector

• Anode and Cathode

• Source, Drain, and Gate

Why is it important to reference the gate pulse to MT1 in a TRIAC?

• To prevent incorrect operation

• To decrease the current

• To ensure the TRIAC conducts in the positive cycle

• To increase the voltage

How does a TRIAC differ from a traditional thyristor?

• It has only two terminals

• It can conduct in both directions

• It cannot be triggered by negative pulses

• It is used only in DC circuits

What happens when a TRIAC is triggered at the zero crossing of the AC waveform?

• It conducts only in the negative half-cycle

• It remains off

• It conducts in both directions

• It conducts only in the positive half-cycle

In the example problem, what is the significance of the delay angle?

• It measures the power output

• It shows the current flow direction

• It indicates the time before the TRIAC conducts

• It determines the maximum voltage

What is the conduction angle in a thyristor circuit?

• The angle at which the thyristor turns off

• The angle at which the current is zero

• The angle during which the thyristor conducts

• The angle at which the voltage is maximum

In the second example problem, what is the role of the diode in the circuit?

• To amplify the signal

• To convert AC to DC

• To drop the voltage by 0.7V

• To increase the current

How is the trigger angle determined in the second example problem?

• By adjusting the resistance

• By calculating the voltage at which the thyristor turns on

• By measuring the current

• By observing the waveform

What is the minimum gate current required to trigger the thyristor in the second example?

• 0.5 mA

• 2 mA

• 0.1 mA

• 1 mA