Most Asked Power Electronics Interview Questions and Answers

Intermediate Power Electronics Questions and Answers

We provide a list of 10 medium level power electronics interview questions in this segment. Examining typical interview questions could enable you to be successful when applying for jobs in this industry.

14. What, in your opinion, is the main application for power electronics?

Ans. Power electronics assists engineers in designing high-efficiency electrical systems for lighting, automation equipment, motor controls, and sophisticated microprocessor utilities. Power electronics concepts can be applied to the following fields:

• Rectifier and inverter applications, 
• Chopper applications,
• Cyclo-converter applications,
• AC to DC, DC to AC, AC to AC, and DC to DC conversion. 

Rectifier and inverter use include 

• Electroplating,
• Improved charging, 
• Variable DC drives, 
• Emergency lighting systems,
• Uninterrupted power supply,
• Frequency converters.

Rectifier and inverter circuits are used to convert AC to DC and DC to AC circuits.

15. Distinguish between a circuit breaker and an isolator?

Ans. Circuit breakers automatically activate in the event of a system error, however, isolators must not be used with a load. Both switches, isolators and circuit breakers, serve connections between circuit components and a power system.
In order to disconnect downstream and upstream circuits when fixing downstream circuits, isolators are manually operated off-loading devices. In the event of overload faults, short circuits, and other failures, circuit breakers are helpful on-load devices for severing circuits. Additionally, isolators have a lower breaking capacity than circuit breakers.

16. What conditions must be met for a gate pulse to activate an SCR?

Ans. The following conditions must be met for an SCR to be activated by a gate pulse:

• The forward-biased mode of SCR should be used between the gate and cathode, a positive gate voltage.
   
• To make sure that the anode current exceeds the latching current, the gate pulse width should be set.

17. What distinguishes holding current from latching current in an SCR?

Ans. The latching current, which is associated with the SCR turn-on procedure, is the minimal current needed by the anode to maintain the forward conduction condition after the gate current has been removed. 

The holding current, which has to be reached by an anode in order for it to achieve an off status, is related to the SCR turn-off process. If the latching current, for instance, is 5 mA, then the holding current can halt conduction if it falls below 5 mA.

18. What are the benefits of a GTO over a traditional thyristor?

Ans. In comparison to a traditional thyristor, a GTO(Gate Turn-off thyristor) has the following advantages:

1. GTO switches more quickly.
    
2. Its ability to handle surge current is comparable to that of an SCR.
    
3. At turn-on, it has a higher di/dt rating.
    
4. GTO circuits are smaller and lighter than SCR circuit units.
    
5. GTO is more effective.
    
6. Due to the removal of commutation chokes, the GTO unit's acoustical, electromagnetic noise has been minimized.

19. What function does the inter group reactor serve in a circuit for a single phase cyclo-converter?

Ans. There will be a net potential difference across the two converters, which causes a circulating current even though the output voltages of the two converters have the same average value and different output voltage waveforms as a function of time. An Inter-group reactor can be inserted to stop this circulating current. Therefore, circulating current is limited using intergroup reactors.

20. For high-frequency applications, which would you pick: MOSFET or IGBT?

Ans. Given that a MOSFET has lower switching losses than an IGBT when used in high-frequency applications doing so may be advantageous. The ideal practice is to limit the frequency range for high-frequency applications to 200 kHz and for low-frequency applications to 20 kHz. The cost advantage of MOSFET over IGBT is another perk of this technology.

21. Why does a single-phase half-controlled bridge rectifier have a higher input power factor than a fully controlled bridge rectifier when both are powering RL loads at the same firing angle?

Ans. Even after having the same firing angle, a single phase half controlled bridge rectifier has a higher input power factor than a fully controlled bridge rectifier because some energy is returned to the source by the inductor in a completely controlled bridge rectifier, the input power factor of a single phase half bridge rectifier is larger than that of a fully controlled bridge rectifier of RL load for the same firing angle.

Consequently, less electricity will be sent to the load. Where supplied power to load/source volt-ampere equals power factor of input supply.

22. What benefits come with using freewheeling diodes?

Ans. The following are the benefits of utilizing freewheeling diodes:

• Improved input power factor Greater load current waveform leads to improved load performance. 
   
• During the freewheeling phase, energy held in L is transferred to R, increasing converter efficiency overall. 
   
• The load voltage V0 is prevented from going negative by the freewheeling diode.

23. Why is stepper motor efficiency so low?

Ans. In contrast to Dc motors, the current consumption of a stepper motor is independent of load. When they are not working at all, they draw the most current. They consequently frequently run hot. At high speeds, the impedance increases, which results in a decrease in the voltage needed to run the constant current control.

Click on the following link to read further: Javascript Interview Questions and Answers

Advanced Power Electronics Questions and Answers

In this section, we offer a list of 10 advanced power electronics interview questions. 

24. Which do you think is better for high voltage applications, MOSFET or IGBT?

Ans. IGBT is required for high-voltage applications. MOSFETs are low voltage electronics, hence. They have a lower voltage rating than IGBT, for example. Generally speaking, MOSFETs are appropriate for applications with breakdown voltages under 250V. Applications with a breakdown voltage of up to 1000V are suitable for IGBTs.

25. What fundamental and necessary specifications must we obtain from the customer in order to construct the buck converter?

Ans. The customer must provide the following information to us:

1. The voltage at Output Voltage input VOUT VIN
    
2. Current Output (load current) IOUT
    
3. Maximum voltage permitted for ripple on the output side
    
4. The converter's effectiveness

26. What benefits does GTO have over SCR?

Ans. Some of the benefits of GTO over Scr are mentioned below:

• Reduction in cost, weight, and volume due to eliminating forced commutation's commutating components.
   
• Reduction of commutation chokes results in a decrease in electromagnetic and acoustic noise.
   
• Increased turn-off speed that allows for high switching frequency.
   
• Improved converter effectiveness.

27. List some of the purposes for a controlled rectifier.

Ans. The purposes of a controlled rectifier are:

• Dc motor drives are used in steel rolling mills, printing presses, textile mills, and paper mills.
   
• Traction DC
   
• Processes involving electrochemistry and electrometallurgy
   
• Drives for portable hand tools
   
• Power sources with magnets
   
• Transmission system using HVDC

28. What does the term "inversion mode" mean?

Ans. The voltage at the dc terminal in a single phase full converter over 900 is negative. Power thus flows from source to load, and the converter functions as a line commutated inverter. Current is positive while source voltage Vs is negative. This is referred to as synchronous mode or inversion mode.

29. What are the various sorts of chopper configurations?

Ans. Choppers can be categorized into the following types based on the direction of the current and voltage.

1. Chopper in the First Quadrant, Type A
    
2. Chopper from the Second Quadrant, Type B
    
3. Type B helicopter with two quadrants or Type C
    
4. A Type C or Type D two-quadrant helicopter
    
5. Type E or four-corner helicopter 

30. Why are thyristors and diodes connected in antiparallel in inverter circuits?

Ans. When the main thyristors are turned off, the diodes linked in antiparallel will still permit the current to flow since the load current for RL loads will not be in phase with the load voltage. This is why we connect thyristors and diodes antiparallel. They are known as feedback diodes.

31. What are some uses for a series inverter?

Ans. At a high output frequency, between 200 Hz and 100 kHz, the thyristorised series inverter generates a waveform that is roughly sinusoidal. Induction heating, sonar transmitters, ultrasonic generators, and fluorescent lights are a few examples of fixed output applications where it is frequently employed.

32. What are the drawbacks of the harmonics present in the inverter system?

Ans. The major drawbacks are the following:

• Harmonic currents will cause the induction motors to overheat. The motor's ability to support a load will be reduced as a result.
   
• Harmonics from power rides can interfere with the operation of the control and regulating circuits if they are not properly protected. This can lead to malfunctions.
   
• Harmonic currents result in losses in the ac system and, on occasion, even resonance. Resonance circumstances may impact the instruments and metering.
   
• Torque pulsation caused by the harmonic current can be helpful on critical loads.

33. Compare CSI and VSI.

Ans.

Frequently Asked Questions

How do I prepare for a power electronics interview?

To prepare for a power electronics interview, first of all, you must clear all your core concepts regarding power electronics. Then, you should look over the previously asked interview questions to find out the pattern and level of the questions. Finally, you should work on you confidence and communication skills.

What are the basic electronics questions asked in interview?

Some primary electronic questions asked in an interview are: What is a passband? What is an ideal voltage source? How and when do you use a resistor? How to use a capacitor? What is a diode? What do you mean by thermal conductivity?

What are the main topics in power electronics?

The main topics in power electronics are electronic circuits, silicon carbide, thermal conductivity, capacitors, diodes, gallium nitride, dielectric material, semiconductor physics, electric motors, mechanical actuators, control systems, electromagnetic devices, etc.

Conclusion

We ended up going over power electronics interview questions in this article, which were divided into easy, medium, and difficult levels. It is an excellent resource for learning about power electronics. We hope these interview questions will assist you in preparing for your dream career.

We advise you to read a few of our interview articles to broaden your knowledge.

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