Industrial electronics
Explainer
The TRIAC: AC Control in One Device
One component can dim a lamp on both halves of the AC wave. How?
Quick check · tap an answer to continue
Lesson notes
Key points
- A TRIAC is a bidirectional thyristor that behaves like two SCRs connected in inverse parallel, sharing a single gate.
- Its terminals are main terminal one, main terminal two and the gate, because it has no fixed anode or cathode.
- It can be triggered in four quadrants, depending on MT2 and gate polarity, though quadrant four needs the most gate current.
- Because it must turn off at every current zero, TRIACs suit low-frequency mains loads like dimmers, fans and heaters.
Definitions
- TRIAC
- Three-terminal thyristor (MT1, MT2, gate) that conducts in both directions once triggered
Takeaway: A TRIAC gives full-wave AC control with one gate.
Quick check: A TRIAC is equivalent to which arrangement?
- Two SCRs in inverse parallel
- Two diodes in series
- An SCR with a diode in series
TRIACMT1, MT2, GateTriggering quadrantsApplications
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