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WorksheetsThyristors
Total questions: 25
Worksheet time: 4mins
The ____ can be externally programmed to turn on at a desired anode-to-gate voltage level.
UJT
PUT
SCR
SCS
You need a very efficient thyristor to control the speed of an AC fan motor. A good device to use would be
SCR
TRIAC
BJT
PUT
An application of _____ is in lighting system for power interruptions.
SCR
SCS
DIAC
TRIAC
Identify the symbol
SCS
PUT
LASCR
TRIAC
The silicon controlled switch is similar in construction to the _____.
TRIAC
DIAC
SCR
IGCT
The _____ can conduct current in either direction and is turned on when a breakover voltage exceeds
SCR
SCS
TRIAC
DIAC
You need to design a relaxation oscillator circuit. The most likely device to use might be
an SCR
a UJT
a TRIAC
a GTO
Identify the diac symbol
A
B
C
D
E
You have a schematic diagram of several types of circuits. Which of these circuits most likely uses a triac?
an oscillator
an ac motor control
a programmable oscillator
an amplifier
What is the maximum breakdown voltage of a diac?
38V
40V
42V
44V
Diac is sometimes called as _______.
SBS
SCS
SCR
LASCR
Identify the type of 4 layer diode.
Zener
Schottky
Shockley
PN junction
The static VI curve for an SCR is plotted for ______.
Ia vs Ig, Va as a parameter
Ia vs Va, with Ig as a parameter
Va vs Ig, with Ia as a parameter
Ig vs Vg, with Ia as a parameter
What is GTO stands for?
Gate turn off
Gate turn on
Gate trigger on
Gate trigger off
SCR were designed to control powers as high as _____
100 MW
10 MW
500 kW
50 kW
The holding current in an SCR can be removed by _____
removing the gate terminal
internally move the SCR to blocking stage
shunt the anode-cathode voltage
commutate the device
Which of the following break down voltages equations are related to DIAC?
VBR1=VBR2±0.1VBR2
VBR1=VBR1±0.1VBR2
VBR1=2VBR2
VBR1=21VBR2
Which of the following is NOT an advantage of SCR as a switch?
the switching speed is very high
the operation does not produce harmonics
it gives noiseless operation at high frequency
it has no moving parts
The SCR is turned off when the anode current is _____ the holding current.
above
equal to
below
twice
A PUT is actually a type of _______ thyristor.
FET device
SCR
TRIAC
UJT
When checking a good SCR or TRIAC with an ohmmeter it will:
show low resistance in both directions
show low resistance when positive on anode and negative on cathode, and high resistance when reversed
show high resistance when positive on anode and negative on cathode, and low resistance when reversed
show high resistance in both directions
The only way to close an SCR is with ________________.
a trigger input applied to the gate
forward breakover voltage
low current drop out
valley voltage
A TRIAC
can trigger only on positive gate voltages
cannot be triggered with gate voltages
can trigger only on negative gate voltages
can be triggered by either a positive or a negative gate voltage
Once a DIAC is conducting, the only way to turn it off is with
breakover voltage
low current drop out
a negative gate voltage
a positive gate voltage
A UJT has
two base leads
one emitter lead
two emitter leads and one base lead
one emitter lead and two base leads
