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Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE) PDF Download

Q21: In the 3-phase inverter circuit shown, the load is balanced and the gating scheme is 180°-conduction mode. All the switching devices are ideal.
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)The rms value of load phase voltage is       (2012)
(a) 106.1V
(b) 141.4V
(c) 212.2V
(d) 282.8V
Ans: 
(b)
Sol: RMS value of line voltage
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Therefore, RMS value of load phase voltage
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q22: A three phase current source inverter used for the speed control of an induction motor is to be realized using MOSFET switches as shown below. Switches S1 to S6 are identical switches.
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)The proper configuration for realizing switches Sto S6 is      (2011)
(a) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
(b) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(c) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(d) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Ans: (c)
Sol: Device used in current source inverter (CSI) must have reverse voltage bloking capacity. Therefore, device such as GTOs, power transistors and power MOSFETs canot be used in a CSI. SO, a diode is added in series with the devices for reverse blocking.

Q23: The Current Source Inverter shown in figure is operated by alternately turning on thyristor pairs (T1, T2) and (T3, T4). If the load is purely resistive, the theoretical maximum output frequency obtainable will be     (2009)
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(a) 125kHz
(b) 250kHz
(c) 500kHz
(d) 50kHz
Ans: 
(b)
Sol: The circuit shown in the figure is a single phase bridge auto sequential commutated inverter (1-phase ASCI).
Thyristor pairs T1, T2 and T3, T4 are alternatively switches to obtain a nearly square wave load current. Two commutating capacitors, one C1 in the upper half and the other C2 in the lower half are connected as shown.
Diodes D1 to Dare connected in series with each SCR to prevent the commutation capacitors from discharging into the load.
THe inverter output frequency is controlled by adjusting the period T through the triggering circuits of thyristors.
The theoretical maximum output frequency obtainable
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q24: A single phase source inverter is feeding a purely inductive load as shown in the figure The inverter is operated at 50 Hz in 180° square wave mode. Assume that the load current does not have any dc component. The peak value of the inductor current i0 will be      (2008)
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(a) 6.37A
(b) 10A
(c) 20A
(d) 40A
Ans:
(b)
Sol: Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Load current increases linearly from −IP to IP during 0 < ωt ≤ π, where IP = peak value of i0
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q25: A 3-phase voltage source inverter is operated in 180° conduction mode. Which one of the following statements is true ?       (2008)
(a) Both pole-voltage and line-voltage will have 3rd harmonic components
(b) Pole-voltage will have 3rd harmonic component but line-voltage will be free from 3rd harmonic
(c) Line-voltage will have 3rd harmonic component but pole-voltage will be free from 3rd harmonic
(d) Both pole-voltage and line-voltage will be free from 3rd harmonic components
Ans: 
(b)
Sol: In 3-phase VSI working in 180° mode
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Pole voltage is a squre wave.
Therefore 3rd harmonic is present in pole voltage.
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)In line voltage waveform even and tripplen harmonics are not present.

Q26: A voltage source inverter is used to control the speed of three-phase, 50 Hz, squirrel cage induction motor. Its slip for rated torque is 4%. The flux is maintained at rated value. If the stator resistance and rotational losses are neglected, then the frequency of the impressed voltage to obtain twice the rated torque at starting should be      (2007)
(a) 10 Hz
(b) 5 Hz
(c) 4 Hz
(d) 2 Hz
Ans: 
(c)

Q27: A single-phase voltages source inverter is controlled in a single pulse-width modulated mode with a pulse width of 150° in each half cycle. Total harmonic distortion is defined as  Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE) where V1 is the rms value of the fundamental component of the output voltage. The THD of output ac voltage waveform is      (2007)
(a) 65.65%
(b) 48.42%
(c) 31.83%
(d) 30.49%
Ans:
(c)
Sol: Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Pulse width = 2d = 150°
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Output voltage in fourier series,
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)RMS value of fundamental component of output voltage,
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Total harmonic Distortion,
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q28: "Six MOSFETs connected in a bridge configuration (having no other power device) must be operated as a Voltage Source Inverter (VSI)". This statement is     (2007)
(a) True, because being majority carrier devices MOSFETs are voltage driven.
(b) True, because MOSFETs hav inherently anti-parallel diodes
(c) False, because it can be operated both as Current Source Inverter (CSI) or a VSI
(d) False, because MOSFETs can be operated as excellent constant current sources in the saturation region.
Ans:
(b)
Sol: As MOSFET have internally antiparallel diodes, MOSFET can not withstand reverse voltage , due to which MOSFET can not be as current source inverter (CSI).

Q29: A single-phase inverter is operated in PWM mode generating a single-pulse of width 2d in the centre of each half cycle as shown in figure. It is found that the output voltage is free from 5th harmonic for pulse width 144°. What will be percentage of 3rd harmonic present in the output voltage (Vo3/Vo1max) ?        (2006)
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(a) 0.00%
(b) 19.60%
(c) 31.70%
(d) 53.90%
Ans: 
(b)
Sol: Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)

Q30: The output voltage waveform of a three-phase square-wave inverter contains     (2005)
(a) only even harmonics
(b) both odd and even harmonic
(c) only odd harmonics
(d) only triple harmonics
Ans:
(c)
Sol: The output voltage in both 180° and 120° conduction mode can be described by the fourier series as follow:
In 180° conduction mode, line output voltage
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)line to neutral output voltage
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)where k = 0, 1, 2...
It is clear from equation (i) to (iv), output voltage wave form contains only odd-harmonic.

Q31: With reference to the output wave form given in the figure, the output of the converter will be free from 5th harmonic when      (2003)
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(a) α = 72°
(b) α = 36°
(c) α = 150°
(d) α = 120°
Ans:
(a)
Sol: To eliminate fifth harmonic,
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q32: An inverter has a periodic output voltage with the output wave form as shown in figure
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)When the conduction angle α = 120°, the rms fundamental component of the output voltage is      (2003)
(a) 0.78 V
(b) 1.10 V
(c) 0.90 V
(d) 1.27 V
Ans:
(a)
Sol: Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Output voltage,
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)R.M.S. value of fundamental component, n = 1
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q33: Figure shows an inverter circuit with a dc source voltage Vs. The semiconductor switches of the inverter are operated in such a manner that the pole voltages V10 and V20 are as shown in figure. What is the rms value of the pole-to-pole voltage V12?    (2002)
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(a) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)

(b) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
(c) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
(d) Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Ans: (b)
Sol: Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)
Q34: A single-phase full-bridge voltage source inverter feeds a purely inductive load, a shown in figure, where T1, T2, T3, T4 are power transistors and D1,  D2,  D3,  D4 are feedback diodes. The inverter is operated in square-wave mode with a frequency of 50 Hz. If the average load current is zero, what is the time duration of conduction of each feedback diode in a cycle?
Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE)(a) 5 msec
(b) 10 msec
(c) 20 msec
(d) 2.5 msec
Ans:
(a)
Sol: Conduction time = T/4 = 20/4 = 5 ms.

The document Previous Year Questions- Inverters - 2 | Power Electronics - Electrical Engineering (EE) is a part of the Electrical Engineering (EE) Course Power Electronics.
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FAQs on Previous Year Questions- Inverters - 2 - Power Electronics - Electrical Engineering (EE)

1. What is an inverter in electrical engineering?
Ans. An inverter is a device that converts direct current (DC) into alternating current (AC) to power various electrical devices.
2. How does an inverter work?
Ans. An inverter works by using electronic components to switch the DC input into AC output, typically using pulse-width modulation (PWM) techniques.
3. What are the common applications of inverters?
Ans. Inverters are commonly used in renewable energy systems, uninterruptible power supplies (UPS), electric vehicles, and household appliances like refrigerators and air conditioners.
4. What are the different types of inverters available in the market?
Ans. The different types of inverters include grid-tied inverters, stand-alone inverters, microinverters, and string inverters, each suited for specific applications.
5. How can one select the right inverter for their specific needs?
Ans. When selecting an inverter, factors to consider include power output requirements, input voltage sources, efficiency ratings, and additional features like surge protection and monitoring capabilities.
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