Chapter 2 Chapter 2 Triode for Alternating Current (TRIAC)
Triac (industrial electronic)
May 22, 2015
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Chapter 2Chapter 2Triode for Alternating Current (TRIAC)
Basic OperationBasic Operation
Triac can conduct current in either direction and formally called bidirectional triode thyristor Closely related to SCRDifferences between Triac and SCR
Triac is bidirectional devices (can conduct current in either direction) while SCR is unidirectional devices (can conduct current only in one way) force commutation by reversed biasing cannot be employed.TRIACs can be triggered by either a positive or a negative current applied to its gate electrode while SCR can only triggered when a positive current apply to the gate terminal
In order to create a triggering current, a positive or negative voltage has to be applied to the gate with respect to the A1 terminal (otherwise known as MT1). EAD 3043 (Industrial Electronic)
Nor Aida Idayu Binti Abdullah. 2012
(a) symbol
(b) Equivalent circuit
Parameter of TRIACParameter of TRIAC
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Comparison between SCR Comparison between SCR and TRIACand TRIAC
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CharacteristicCharacteristic
It can be seen that it is an extension IV characteristic of SCR
The characteristic are symmetrical about the first and the third quadrants
It shows the gate can be used to control the main current flow in either direction
TRIAC will be continuously ON until the current through A1 to A2 are below the holding current EAD 3043 (Industrial Electronic)
Nor Aida Idayu Binti Abdullah. 2012
EAD 3043 (Industrial Electronic)Nor Aida Idayu Binti Abdullah. 2012
Triggering MethodTriggering Method
The phase shifting method of firing TRIAC is similar to the firing of the SCR
The major difference in the waveform is there is a negative portion in the waveform of TRIAC
It shows the gate can be used to control the main current flow in either direction
Turning the TRIAC ONTurning the TRIAC ON
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ExampleExample
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ExampleExample
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ExerciseExercise
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ExerciseExercise
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QuizQuiz
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AssignmentAssignment
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