Sunday, September 23, 2012

Power Electronics Objective Questions with Answers: Part 5

[1]which of the following statements are true about VI characteristic of SCR?
A. Holding current is more than Latching current
B. SCR will trigger if the applied voltage exceeds forward break over voltage
C. SCR can be triggered without gate current
D. When the SCR is in reverse biased, small leakage current will flow
Options:
a. A, B and C
b. All are true
c. B, C, D
d. C, D

[2] which of the following statements are true about BJT?
(i) It has more power handling capability than MOSFET
(ii) Has higher switching speed than IGBT and MOSFET
(iii) Has low on state conduction resistance
(iv) Has second breakdown voltage problem  
Options:
a. All are true
b. (i), (ii), (iii) and (iv)
c. (i), (iii) and (iv)
d. (ii), (iii) and (iv)

[3] For a JFET, when VDS is increased beyond the pinch off voltage, the drain current
a. Increases
b. Decreases
c. Remains constant
d. First decreases and then increases

[4] n-channel FETs are superior to P-channel FETs, because
a. They have higher input impedance
b. They have high switching time
c. They consume less power
d.  Mobility of electrons is greater than that of holes

[5] Which of the following is true about the diodes
a. During forward biased small amount of voltage drop will appear across anode and cathode
b. If the reverse voltage exceed VRRM the diode will destroy
c. trr is depends on softness factor
d. schottky diodes have low trr
Options:
(i) All are true
(ii) A, B, D
(iii) A, B,C
(iv) B,C, D

The feature of schottky diode is low forward voltage drop, not low trr.

[6] The MOSFET has
(i) Higher Power handling capability than BJT
(ii) Faster switching speed than BJT
(iii) High on state resistance
(iv) Secondary breakdown voltage problem
which of the above statements are incorrect?
Options:
a. (i), (iii), (iv)
b. (ii), (iii)
c. All of the above
d. (ii), (iii), (iv)

[7] Which of the following is called as uncontrolled semiconductor device?
a.  Diode
b. Thyristor
c.  GTO
d.  MOSFET

[8] Which of the following is a half controlled semiconductor device?
a. MOSFET
b. GTO
c. MCT
d. SCR 

In SCR only turn on of the device an be controllable by the gate signal.

[9]Which of the following abbreviation is not a power semiconductor device?
a. SIT
b. SITH
c. MCT
d. IGCT
 Options:
1. a and d
2. a only
3. a, b, d
4. All are power semiconductor device

SIT – Static Induction Transistor
SITH – Static Induction Thyristor
MCT -  MOS Controlled Thyristor
IGCT – Integrated Gate Commutated Thyristor

[10] Which of the following statements are correct?
a. IGBT is current driven device
b. IGCT is voltage driven device
c. MOSFET is voltage driven device
d. GTO is minority carrier device
Options:
1. a, b, c
2. b, c, d
3. All are correct
4. None are correct
5:57 PM

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