MCQs of DC-DC converters - Switching Voltage Regulators (Power Electronics - 3140915)

Power Electronics (3140915) MCQs

MCQs of DC-DC converters - Switching Voltage Regulators

Showing 41 to 50 out of 51 Questions

41.

For the step down chopper shown in the figure below, Vs = 100 V and the duty cycle of the switch is 0.8. The load is sufficiently inductive so that the load current is ripple free. The average current through the diode (D) under steady state is

(a)	2 A
(b)	1.6 A
(c)	8 A
(d)	6.4 A

42.

A chopper circuit is fed from an input voltage of 20 V delivers a power of 16 watts. If the chopper efficiency is 80 %, then find the value of input current.

(a)	0.64 A
(b)	1 A
(c)	0.8 A
(d)	1.25 A

43.

In dc choppers, if Ton is the on-period and f is the chopping frequency, then output voltage in terms of input voltage Vs is given by

(a)	Vs . (Ton/f)
(b)	Vs . (f/Ton)
(c)	(Vs/f) . Ton
(d)	Vs . f . Ton

44.

In dc choppers, the waveforms for input and output voltages are respectively

(a)	discontinuous, continuous
(b)	both continuous
(c)	both discontinuous
(d)	continuous, discontinuous

45.

In PWM method of controlling the average output voltage in a chopper, the on-time is ____________ but the chopping frequency is ____________.

(a)	varied, varied
(b)	varied, kept constant
(c)	kept constant. varied
(d)	kept constant, kept constant

46.

In FM method of controlling the average output voltage in a chopper, chopping period is ______________ but on-time is _______________or off-time is __________________.

(a)	varied, kept constant, kept constant
(b)	kept constant, varied, varied
(c)	kept constant, kept constant, varied
(d)	varied, varied, varied

47.

For step-down chopper, Vs is the source voltage, R is the load resistance and &delat; is the duty cycle. The average output voltage and current for this chopper are respectively

(a)	δ.Vs , δ . (Vs/R)
(b)	(1-δ) . Vs , (1-δ) . Vs/R
(c)	Vs/δ , Vs/δR
(d)	Vs/(1-δ) , Vs/(1-δ)R

48.

A chopper has Vs as the source voltage, R as the load resistance and &delat; as the duty cycle. For this chopper, rms value of output voltage is

(a)	$δ . V_{s}$
(b)	$\sqrt{δ} . V_{s}$
(c)	$V_{s} / \sqrt{δ}$
(d)	$\sqrt{1 - δ} . V_{s}$

49.

For a chopper, Vs is the source voltage, R is the load resistance and δ is the duty cycle. Rms and average values of thyristor currents for this chopper are

(a)	$δ . \frac{V_{s}}{R}, \sqrt{δ} . \frac{V_{s}}{R}$
(b)	$\sqrt{δ} . \frac{V_{s}}{R}, \sqrt{δ} . \frac{V_{s}}{R}$
(c)	$\sqrt{δ} . \frac{V_{s}}{R}, δ . \frac{V_{s}}{R}$
(d)	$\sqrt{1 - δ} . \frac{V_{s}}{R}, (1 - δ) . \frac{V_{s}}{R}$

50.

In dc choppers, per unit ripple is maximum when duty cycle δ is

(a)	0.2
(b)	0.5
(c)	0.7
(d)	0.9

Showing 41 to 50 out of 51 Questions