Electronics and Electrical Engineering interview Question and Answers for fresh engineers (Part 1)
Question1: Is it possible to start up a 36w or 40w 220V AC/DC tube light without the help of Coil or Choke?
Answer 1: It is not possible without the help of electric coil or choke. Because, the coil or choke ionize the particles in the tube light. In normal voltage it is not possible to ionize the particle.
Question2: What is the difference between three point and four point starters?
Answer 2: In the four point starter the line and Shunt are connected separately. In the three point starter the line and shunt are connected in same. This is one of the advantages of three point starter.
Question 3: What types of resistance is used in bulbs or tube lights? What will happen if a 220volt AC operated bulb or device run by the 220volt DC?
Answer 3: The AC operated Bulb or device has a very low resistance. But, the devices whose are designed for AC offers high impedance to the supply. When the DC voltage is applied to the AC devices, the passing DC current is very high due to the low resistance of the device. This high voltage may damage the device.
Question 4: What do you mean by electric traction?
Answer 4: Electric Traction means running a machine by using electric energy or power. Electrical energy, energies the traction system. Basically DC motors are used in traction system. Now electric traction system widely used in trams, trolleys, industries, railways .Bullet train is also running by the magnetic traction, magnetism is setup by the electric energy in the bullet train.
Question 5: Why the capacitor works doesn’t work on DC?
Answer 5: The capacitor normally gives an infinite resistance to DC component. But, it allows AC power component to pass through the devices. These resistances of the capacitor blocks work of DC component.
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Electrical engineering interview topic:Job interview and viva Topics for Electrical and electronics Engineers (Part-4).
In this topic we know about Power System Stability,Steady State Stability,Static Stability,Dynamic Stability and Steady State Stability Criterion
13. Power System Stability:
In the large power system there might be some disturbance always. The system has the tendency for the system to develop forces for bringing the system in a normal or stable condition. The ability of the system to obtain the normal or stable condition after getting disturbed is called Power System Stability.
The stability has mainly two types:
1. Steady State Stability.
2. Transient Stability.
14. Steady State Stability:The ability of being stable after a small disturbance in the system is called Steady State Stability.
The Steady State Stability is concerned with the very small power changes .which are changed gradually.
The Steady State Stability has two types:
1. Static Stability
2. Dynamic Stability.
· Static Stability:In the Static Stability there is a large duration phenomenon with small disturbance. This is the inherent stability that can achieve with out the help of automatic control devices.
· Dynamic Stability:In the Dynamic Stability there is a small duration phenomenon with large disturbance. This Dynamic Stability refers to artificial stability. This artificial stability is given to an inherently unstable system by the help of automatic control devices.
15. Steady State Stability Criterion:The rate (dP/dδ) of the differential power increased is obtained per differential load angle increased. This are called as electrical stiffness or the synchronizing power coefficient of a synchronous machine. This is considered as the measure of the stability of the system.
The Steady State Stability has basically three Criterion or state.
· (dP/dδ) > 0 ; Direct State Synchronous Stability.
· (dP/dδ) = 0 ; Steady State Stability.
· (dP/dδ) < 0 ; The System is unstable.
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Electronics and Electrical Engineering interview Question and Answers for fresh engineers (Part 7)
In this topic we know about the Power Factor, the leading and lagging condition for the power factor, the disadvantage of the low Power Factor and the main causes of the low power factor.
Question: What is Power Factor?
Answer: In an a.c. circuit the cosine of angle between voltage and current is called as power factor.
|Fig: Power factor angles|
Question: What are the leading and lagging conditions in the power factor improvement?
Answer: Normally there are two types of circuit, capacitive and inductive circuits.
· In the capacitive circuits, current leads the voltage and power factor is called as leading.
· In the inductive circuits, current lags behinds the voltage and power factor is called as lagging.
Question: What are the disadvantages of low power factor?
Answer: The main disadvantages of low power factor are as follows,
1. Large size of the Conductor.
2. Large Kilo Volt Ampere rating of the electrical machinery or equipment.
3. Poor or unaccepted voltage regulations.
4. A big amount of Copper loss.
5. The handling capacity of the system reduced.
Question: What are the main causes of the low power factor?
Answer: In the supply system normally the power factor is lower then 0.8 for the overall load. Low Power factor is very undesirable, because it hampers the economic parameters for the power generation and distribution. Now, some short important causes are as follows,
· In the low lagging factor some electrical equipment such as electric discharge lamps, Arc lamps and the industrial heating furnaces are running.
· The power factor is also depending on the load conditions. The load is varying time to time. The supply voltage is increasing in the low load period which increases the amount of the magnetization current. This magnetizing current is resulting in the decreased power factor.
· The single phase and three phase ac motors have low lagging power factor and they are induction type also. The power factor is varying for these types of motor. It can run from 0.2 to 0.9 values depends on load. In the heavy load the power factor can be 0.8 or 0.9 and in the light load the power factor can be 0.2 to 0.3.
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