# Electrical Engineering: Power Electronics MCQ

##### 6. Question

A phase controlled single phase rectifier, supplied by an AC source, feeds power to an R-L-E load as shown in the figure. The rectifier output voltage has an average value given by Vo = Vm(3 + cosα) / 2π ,where Vm = 80π volts and α is the firing angle. If the power

delivered to the lossless battery is 1600 W, α in degree is________ (up to 2 decimal places).

Answer

##### 7. Question

In the circuit shown in the figure, the bipolar junction transistor (BJT) has a current gain β = 100. The base-emitter voltage drop is a constant, V_{BE} = 0.7V. The value of the Thevenin equivalent resistance R_{Th} (in Ω) as shown in the figure is ______ (up to 2 decimal places).

Answer

##### 8. Question

For the circuit shown below, assume that the OPAMP is ideal.

Which one of the following is TRUE?

Answer

##### 9. Question

In the circuit shown all elements are ideal and the switch S is operated at 10 kHz and 60% duty ratio. The capacitor is large enough so that the ripple across it is negligible and at steady state acquires a voltage as shown. The peak current in amperes drawn from the 50 V DC source is ________ . (Give the answer up to one decimal place.)

Answer

##### 10. Question

The figure below shows the circuit diagram of a controlled rectifier supplied from a 230 V, 50 Hz, 1-phase voltage source and a 10:1 ideal transformer. Assume that all devices are ideal. The firing angles of the thyristors T 1 and T 2 are 90º and 270º, respectively.

Answer