cameroon gce advanced level 2025 power electronics 1

Based on the image provided, here is the extracted data, which includes a set of multiple-choice questions related to power electronics, specifically focusing on thyristors, choppers, and rectifiers.

Question 1

A thyristor (SCR) is a:

A. P-N-P-N device

B. P-N-P-N device

C. N-P-N-P device

D. P-N-P device

Question 2

A chopper is a:

A. Time ratio controller

B. AC to DC converter

C. DC transformer

D. High speed semiconductor switch

Question 3

In the circuit of Figure 1, the SCR is triggered at a certain firing angle α. The load current falls to zero at ωt equals to

A. α

B. α/2

C. π

D. π/2

Question 4

A single-phase half wave circuit has Vs​=230 V with a load R of 100 Ω. The average load current at α=30∘ is

A. 1.45 A

B. 0.57 A

C. 0.96 A

D. 2.3 A

Question 5

The circuit given in Figure 2 is that of

A. Half wave series inverter

B. Full wave series inverter

C. Half wave bridge inverter

D. Half wave parallel inverter

Question 6

Single phase half bridge inverters require

A. two wire ac supply

B. two wire dc supply

C. three wire ac supply

D. three wire dc supply

Question 7

The load voltage of a chopper can be controlled by varying the:

A. Firing angle

B. Resistor position

C. Excitation angle

D. Duty cycle

Question 8

The duty cycle of a chopper is

A. Ton​/Toff​

B. Ton​×Toff​

C. T/Toff​

D. Ton​/T

Question 9

Inverters convert:

A. DC power to DC power

B. AC power to AC power

C. AC power to DC power

D. DC power to AC power

Question 10

A cyclo-converter is

A. One stage power converter

B. One stage voltage converter

C. One stage frequency converter

D. Proportional stage converter

Question 11

If the firing angle becomes negative, the the rectifier begins to work as:

A. A rectifier

B. An inverter

C. A chopper

D. A regulator

Question 12

In a three-phase bridge rectifier the ripple frequency is:

A. Equal to the input frequency

B. Twice the input frequency

C. Three times the input frequency

D. Six times the input frequency

Question 13

In a three-phase half wave rectifier, when firing angle is less than 90 degree, then the average dc output voltage becomes:

A. positive

B. negative

C. inductive

D. zero

Question 14

A three-phase bridge inverter requires minimum of:

A. 3 switching devices

B. 4 switching devices

C. 6 switching devices

D. 8 switching devices