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POWER ELECTRONICS Questions and Answers pdf free download mcqs interview objective type important 2 mark questions for eee ece. Power Electronics Objective Questions 1. Questions & Answers on Diodes The P-N Junction Power Diode – Part 1 Power Diode – Part 2 Types of Power Diodes . Our + Power Electronics questions and answers focuses on all areas of Power + Multiple Choice Questions & Answers in Power Electronics with.
Mohammad Al Rshdan. What is meant by positive converter group in a cycloconverter? What is meant by step-up cyclo-converters? False Answer: What are the applications of cyclo-converter? Nitesh Kumar. Directly proportional to their harmonic order b.
Triangular AC output voltage d. Trapezoidal AC output voltage. Square AC output voltage. Two dimensional functions b. Three dimensional functions c. One dimensional functions d. Two dimensional functions. Zero b. AC — AC converters b. AC — DC converters c.
DC — AC converters d. DC — DC converters. The amplitudes are a. Directly proportional to their harmonic order b. Inversely proportional to their harmonic order c. Not related to their harmonic order d. Inversely proportional to their harmonic order. Does not contains second harmonic b. Does not contains third harmonic c. Does not contains fifth harmonic d.
Does not contains seventh harmonic. Does not contains second harmonic. Identical to line voltage in a VSI b. Identical to line current in VSI c. Identical to phase voltage in VSI d. Identical to phase voltage in CSI. Identical to line voltage in a VSI.
One b. Three c. Six d. Dependent on the load current b. Dependent on the voltage c. Dependent on both the load current and load voltage behind the short circuit current d. Independent on both the load current and load voltage. Large overlapping takes place b. Small overlapping operation c. No overlapping operation d. No overlapping operation. Suppressing emissions b. Reducing the efficiency of the coupling path c. Reducing the susceptibility of the receptor d.
Decays as R, where R is the separation distance between the emitter and the receptor c. Decays as 2R, where R is the separation distance between the emitter and the receptor. Is equal to the source resistance b. Greater than the source resistance c.
Smaller than the source resistance d. Is equal to the source resistance. Decrease with frequency b. Remains same with change in frequency c. Increase with frequency d. Either a or b. Increase with frequency. Diode and capacitor b. Capacitor and SCR c. Inductor and capacitor d.
Capacitor and load. Diode and capacitor. Symmetric triangular voltage across itself b. Symmetric rectangular voltage across itself c. Symmetric trapezoidal voltage across itself d. Symmetric sinusoidal voltage across itself. Symmetric trapezoidal voltage across itself. Voltage across the commutating inductances collapses b. The capacitance voltage adds to the supply voltage c. Both a and b d. Both a and b. LISN stands for a. Line integrated stabilization network b. Line impedance stabilization network c.
Line integrated stored network d. Voltage commutated chopper. Current commutated chopper. Load commutated chopper. What is meant by voltage commutation? In this process, a charged capacitor momentarily reverse biases the conducting thyristor and turn it off.
What is meant by current commutation? In this process, a current pulse is made to flow in the reverse direction through the conducting thyristor and when the net thyristor current becomes zero, it is turned off.
What is meant by load commutation? In this process, the load current flowing through the thyristor either becomes zero or is transferred to another device from the conducting thyristor.
What are the advantages of current commutated chopper? The capacitor always remains charged with the correct polarity. Commutation is reliable as load current is less than the peak commutation current ICP.
The auxiliary thyristor TA is naturally commutated as its current passes through zero value. What are the advantages of load commutated chopper?
Commutating inductor is not required. It is capable of commutating any amount of load current. It can work at high frequencies in the order of kHz. Filtering requirements are minimal. What are the disadvantages of load commutated chopper? For high power applications, efficiency becomes very low because of high switching losses at high operating frequencies.
Freewheeling diode is subjected to twice the supply voltage. Peak load voltage is equal to twice the supply voltage. The commutating capacitor has to carry full load current at a frequency of half chopping frequency.
One thyristor pair should be turned-on only when the other pair is commutated. This can be realized by sensing the capacitor current that is alternating. What is meant by inverter? A device that converts dc power into ac power at desired output voltage and frequency is called an inverter. What are the applications of an inverter? Adjustable speed drives b. Induction heating c. Stand-by aircraft power supplies d. UPS e. HVDC transmission What are the main classification of inverter? Voltage Source Inverter b.
Current Source Inverter Why thyristors are not preferred for inverters? Thyristors require extra commutation circuits for turn off which results in uncreased complexity of the circuit. For these reasons thyristors are not preferred for inverters. How output frequency is varied in case of a thyristor? The output frequency is varied by varying the turn off time of the thyristors in the inverter circuit, i.
Give two advantages of CSI. CSI does not require any feedback diodes.
Commutation circuit is simple as it involves only thyristors. What is the main drawback of a single phase half bridge inverter? It require a 3-wire dc supply. Why diodes should be connected in antiparallel with thethyristors in inverter circuits?
For RL loads, load current will not be in phase with load voltage and the diodes connected in antiparallel will allow the current to flow when the main thyristors are turned off. These diodes are called feedback diodes. What types of inverters require feedback diodes? VSI with RL load. What is meant a series inverter?
An inverter in which the commutating elements are connected in series with the load is called a series inverter. What is the condition to be satisfied in the selection of L and C in a series inverter? What is meant a parallel inverter? An inverter in which the commutating elements are connected in parallel with the load is called a parallel inverter. What are the applications of a series inverter? The thyristorised series inverter produces an approximately sinusoidal waveform at a high output frequency, ranging from Hz to kHz.
It is commonly used for fixed output applications such as a. Ultrasonic generator. Induction heating. Sonar Transmitter d. Fluorescent lighting. How is the inverter circuit classified based on commutation circuitry?
Line commutated inverters. Load commutated inverters. Self commutated inverters. Forced commutated inverters. What is meant by McMurray inverter? It is an impulse commutated inverter which relies on LC circuit and an auxiliary thyristor for commutation in the load circuit. What are the applications of a CSI? Induction heating b. Lagging VAR compensation c. Speed control of ac motors.
Synchronous motor starting. What is meant by PWM control? In this method, a fixed dc input voltage is given to the inverter and a controlled ac output voltage is obtained by adjusting the on and off periods of the inverter components. This is the most popular method of controlling the output voltage and this method is termed as PWM control. What are the advantages of PWM control? The output voltage can be obtained without any additional components.
Lower order harmonics can be eliminated or minimized along with its output voltage control. As the higher order harmonics can be filtered easily, the filtering requirements are minimized. What are the disadvantages of the harmonics present in the inverter system? Harmonic currents will lead to excessive heating in the induction motors.
This will reduce the load carrying capacity of the motor. If the control and the regulating circuits are not properly shielded, harmonics from power ride can affect their operation and malfunctioning can result.
Harmonic currents cause losses in the ac system and can even some time produce resonance in the system. Under resonant conditions, the instrumentation and metering can be affected.
On critical loads, torque pulsation produced by the harmonic current can be useful. What are the methods of reduction of harmonic content? Transformer connections b. Sinusoidal PWM c. Multiple commutation in each cycle d. Stepped wave inverters. Input voltage is maintained constant Input current is constant but adjustable 2.
The output voltage does not depend on the load The output current does not depend on the load 3. The magnitude of the output current and its waveform depends on the nature of the load impedance The magnitude of the output voltage and its waveform depends on the nature of the load impedance 4.
It requires feedback diodes It does not requires feedback diodes 5. Commutation circuit is complicated i. Commutation circuit is simple i. What are the disadvantages of PWM control? SCRs are expensive as they must possess low turn-on and turn-off times. What does ac voltage controller mean? It is device which converts fixed alternating voltage into a variable voltage without change in frequency.
What are the applications of ac voltage controllers? Domestic and industrial heating b. Lighting control c. Speed control of single phase and three phase ac motors d. Transformer tap changing What are the advantages of ac voltage controllers? Flexibility in control c. Less maintenance What are the disadvantages of ac voltage controllers?
The main draw back is the introduction of harmonics in the supply current and the load voltage waveforms particularly at low output voltages. What are the two methods of control in ac voltage controllers?
ON-OFF control b. Phase control ON-OFF control: In this method, the thyristors are employed as switches to connect the load circuit to the source for a few cycles of the load voltage and disconnect it for another few cycles. Phase control: In this method, thyristor switches connect the load to the ac source for a portion of each half cycle of input voltage. Due to zero-voltage and zero current switching of thyristors, the harmonics generated by the switching action are reduced.
This type of control is applicable in systems that have high mechanical inertia and high thermal time constant. What is meant by unidirectional or half-wave ac voltage controller? Here the power flow is controlled only during the positive half-cycle of the input voltage. What are the disadvantages of unidirectional or halfwave ac voltage controller? Due to the presence of diode on the circuit, the control range is limited and the.
The input current and output voltage are asymmetrical and contain a dc component. If there is an input transformer, sdaturation problem will occur c. It is only used for low power resistive load. What is meant by bidirectional or half-wave ac voltage controller?
Here the power flow is controlled during both cycles of the input voltage. What is the control range of firing angle inac voltage controller with RL load? What type of gating signal is used in single phase ac voltage controller with RL load? High frequency carrier gating signal is used for single phase ac voltage controller with RL load.
What are the disadvantages of continuous gating signal? More heating of the SCR gate. Increases the size of pulse transformer. What is meant by high frequency carrier gating? Thyristor is turned on by using a train of pulses from to. This type of signal is called as high frequency carrier gating. What is meant by sequence control of ac voltage regulators?
It means that the stages of voltage controllers in parallel triggered in a proper sequence one after the other so as to obtain a variable output with low harmonic content. What are the advantages of sequence control of ac voltage regulators? System power factor is improved. Harmonics are reduced in the source current and the load voltage. What is meant by cyclo-converter? It converts input power at one frequency to output power at another frequency with one-stage conversion.
Cycloconverter is also known as frequency changer. What are the two types of cyclo-converters? Step-up cyclo-converters b.
Step-down cyclo-converters What is meant by step-up cyclo-converters? In these converters, the output frequency is less than the supply frequency. What is meant by step-down cyclo-converters? In these converters, the output frequency is more than the supply frequency.
What are the applications of cyclo-converter?
Speed control of high power ac drives c. Static VAR generation d. Power supply in aircraft or ship boards. What is meant by positive converter group in a cycloconverter? The part of the cycloconverter circuit that permits the flow of current during positive half cycle of output current is called positive converter group.
What is meant by negative converter group in a cycloconverter? The part of the cycloconverter circuit that permits the flow of current during negative half cycle of output current is called negative converter group. Flag for inappropriate content. Related titles. Digital Signal Processing short question and answers.
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