Features of the Triac

Question 1

Where the SCR is a unidirectional device, a Triac is a _______ device

Answer 1

bi-directional

Question 2

In general, Triac’s have ______ (higher/lower) current ratings than SCR’s

Answer 2

lower

Question 3

Name one common application for a Triac

Answer 3

lamp dimming; domestic range hot plate control; smaller motor speed control; applications that do not need high current

Question 4

In some (but not all) Triacs, how is the gate terminal readily identified?

Answer 4

smaller than the other two leads

Question 5

The voltage drop across a Triac, when conducting rated current, would be closest to:

a. 0.7 V
b. 1 V to 2 V
c. 5 V
d. 12 V

Answer 5

b. 1 V to 2 V

Question 6

Can a Triac be triggered into conduction without a gate signal? Explain.

Answer 6

yes, by raising the voltage across the main terminals high enough (breakover), or by a rapid rise in voltage across the main terminals (dv/dt)

Question 7

What is meant by the Triac holding current?

Answer 7

current required to keep the Triac on without the gate signal

Question 8

The action of a Trial could be likened to two ____ connected back to back

Answer 8

SCR’s

Question 9

Triacs are available in rms current ratings up to a maximum of about ____ A

Answer 9

45 A

Question 10

When testing a Triac, the ohmmeter should read:

a. ______ (continuity/high resistance) before the jumper lead is connected, and
b. ______ (continuity/high resistance) after the jumper lead is connected

Answer 10

a. high resistance

b. continuity