Compare SCR and TRIAC
SCR
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TRIAC
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It is an unidirectional device.
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It is a bidirectional device.
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It is turned-on by only positive gate current.
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It can be turned-on by either positive or negative gate current.
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Operates only in the first quadrant
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Operates in either 1 st or 3rd quadrant.
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Anti-parallel SCRs are used for bidirectional current flow.
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TRIAC is equivalent to a pair of antiparallel connected SCRs.
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It has better gate-current sensitivity.
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It has poor gate-current sensitivity as compared to SCR.
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It has lower turn-on & turn-off times as compared to TRIAC.
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It has higher turn-on & turn-off times as compared to SCR.
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For bidirectional current applications, two SCRs & two heat sinks require more space.
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For bidirectional current applications, one TRIAC & one heat sink require less space.
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Firing circuit design is simple.
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More careful firing circuit design is required.
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Higher voltage & current ratings as compared to TRIAC.
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Lower voltage & current ratings as compared to SCR.
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It is employed in large power applications including large power supplies, DC motor drives, lighting and heating, Static VAR compensators, Electronic circuit breakers etc. |
It is employed in low and medium power applications including lamp dimmer, heating control, zero voltage switched AC relay, small AC motor control etc.
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