Electrical Engineering Interview Questions and Answers
1. What happens if I connect a capacitor to a generator load?
Answer : Connecting a capacitor across a generator always improves power factor, but it will help depends up on the engine capacity of the alternator, otherwise the alternator will be overloaded due to the extra watts consumed due to the improvement on pf. Secondly, don't connect a capacitor across an alternator while it is picking up or without any other load.
2. Why the capacitors works on AC only?
Answer: Generally capacitor gives infinite resistance to dc components (i.e., block the DC components). It allows the ac components to pass through.
3. Explain the working principal of the circuit breaker?
Answer: Circuit breaker is the one which makes or breaks the circuit. It has two contacts namely fixed contact and moving contact. In normal condition moving contact comes in contact with the fixed contact thus forming the closed contact for the flow of current. In case of abnormal and faulty conditions (when the current exceeds the rated value), an arc occurs between the fixed and moving contacts and thus forms the open circuit. The arc is extinguished by the arc extinguishing media such as air, oil, vacuum, etc.
4. How many types of colling system it transformers?
Answer:
a. ONAN (oil natural, air natural)
b. ONAF (oil natural, air forced)
c. OFAF (oil forced, air forced)
d. ODWF (oil direct, water forced)
e. OFAN (oil forced, air forced)
5. What is the function of anti-pumping in circuit breaker?
Answer: When the circuit breaker is closed at one time by the closing pushbutton, the anti-pumping contactor prevents the circuit breaker from being reclosed by the closing pushbutton after it is already closed.
6. What is stepper motor? What is its uses?
Answer: Stepper motor is the electrical machine which act upon input pulse applied to it.it is one type of synchronous motor which runs in steps in either direction instead of running in complete cycle.so, in automation parts it is used.
7. Tell me in detail about c.t. and p.t.?
Answer: The term C.T means current transformer, and the term P.T means potential transformer. In circuit where measurements of high voltage and high current is involved, they are used there.
In particular, when a measuring device like a voltmeter or ammeter is not able to measure such a high value of the quantity due to a high value of the torque, it can damage the measuring device. Thus, CTs and PTs are introduced into the circuits. They work on the same principle as the transformer, which is based on the connection of the electromagnetic flux produced by the primary with the secondary. They work according to the ratio in which they are designed.
8. There are a Transformer and an induction machine. Those two have the same supply. For which device the load current will be maximum? And why?
Answer: The motor has max load current compare to that of transformer because the motor consumes real power and the transformer is only producing the working flux and it’s not consuming. Hence the load current in the transformer is because of core loss so it is minimum.
9. What is power factor? Whether it should be high or low? Why?
Answer: Power factor should be high in order to get smooth operation of the system. Low power factor means losses will be more.it is the ratio of true power to apparent power. It has to be ideally 1. If it is too low then cable over heating &equipment overloading will occur. If it is greater than 1 then load will act as capacitor and starts feeding the source and will cause tripping. (If pf is poor ex: 0.17 to meet actual power load has to draw more current (V constant), result in more losses if pf is good ex: 0.95 to meet actual power load has to draw less current (V constant), result in less losses)
10. What is the difference between Isolator and Circuit Breaker?
Answer: Isolator is an off load device which is used for isolating the downstream circuits from upstream circuits for the reason of any maintenance on downstream circuits. It is manually operated and does not contain any solenoid unlike circuit breaker. It should not be operated while it is having load. First the load on it must be made zero and then it can safely operate. Its specification only rated current is given. But circuit breaker is on load automatic device used for breaking the circuit in case of abnormal conditions like short circuit, overload etc., it is having three specification 1 is rated current and 2 is short circuit breaking capacity and 3 is instantaneous tripping current .
11. What is Boucholz relay and the significance of it in to the transformer?
Answer: Boucholz relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. whenever any internal fault occurs in a transformer, the Boucholz relay at once gives a horn for some time, if the transformer is isolated from the circuit then it stop its sound itself otherwise it trips the circuit by its own tripping mechanism.
12. What is SF6 Circuit Breaker?
Answer : SF6 is Sulphur hexa Fluoride gas. If this gas is used as arc quenching medium in a Circuit breaker means SF6 CB
13. Describe the ferrantic effect.
Answer : The voltage at the receiving end is higher than the voltage at the transmitting end, or the output voltage is higher than the input voltage.
14. What does cable insulation voltage mean? Describe it.
Answer : In response, the ability of a cable to sustain applied voltage without breaking is referred to as the insulation level of the cable.
15. Why we do 2 types of earthing on transformer (i.e. :) body earthing & neutral earthing, what is function. i am going to install a 5oo kva transformer & 380 kva DG set what should the earthing value?
Answer: The two types of earthing are Familiar as Equipment earthing and system earthing. In Equipment earthing: body (non-conducting part) of the equipment should be earthed to safeguard the human beings. System Earthing: In this neutral of the supply source (Transformer or Generator) should be grounded. With this, in case of unbalanced loading neutral will not be shifted.so that unbalanced voltages will not arise. We can protect the equipment also. With size of the equipment (transformer or alternator) and selection of relying system earthing will be further classified into directly earthed, Impedance earthing, resistive (NGRs) earthing.
16. Where can I use MCCB and what is the difference between it and MCB?
The answer is that MCBs, or micro circuit breakers, are thermally driven and used in circuits with small current ratings to prevent short circuits. MCCB circuit breakers have molded cases and are magnetically operated for instantaneous trip in the event of a short circuit and thermally operated for over load current. There could be built-in undervoltage and underfrequency. It is typically utilized in situations where the average current exceeds 100A.
17. How does a lockout relay work with high voltage?
The e-stop switch is usually positioned either before or after a lock-out relay so that electricity can be cut off at a single, central point. This relay is powered by the same electrical source as the control power and is operated by a key lock switch. The relay itself may have up to 24 contact points within the unit itself. This allows the control power for multiple machines to be locked out by the turn of a single key switch.
18. What is the difference between earth resistance and earth electrode resistance?
Answer: Only one of the terminals is obvious in earth resistance. In order to find the second terminal, we must resort to its definition: Earth resistance is the resistance existing between the electrically accessible part of a buried electrode and another point on the earth, which is far away. The resistance of the electrode has the following components: (A) The resistance of the metal and that of the connection to it. (B) The contact resistance of the surrounding earth to the electrode.
19. Which power plant has a high load factor?
All base load power plants have a high load factor. If we use high efficiency power plants to supply the base load, we can reduce the cost of production. Hydroelectric power plants have a higher efficiency than thermal and nuclear power plants.
20. Why does an AC solenoid valve attract the piston even if we interchange the terminal? Will the poles change?
Answer: Yes, because the poles change in every half cycle of AC voltage, so the polarity of AC voltage changes continuously in every half cycle. Thus, the interchangeability of terminals in an AC system does not have any difference. That is why the AC solenoid attracts the plunger even if its terminals are interchanged.
21. Definition of IDMT relay?
Answer: It is an inverse definite minimum time relay. In an IDMT relay, its operation is inversely proportional and is also a characteristic of the minimum time after which this relay operates. It is inverse in the sense that the tripping time decreases as the magnitude of the fault current increases.
22. What are the losses of transformer?
Answer: TRANSFORMER LOSSES - Transformer losses have two sources: copper loss and magnetic loss. Copper losses are caused by the resistance of the wire (I2R). Magnetic losses are caused by
Eddy currents and hysteresis in the core. Copper loss is a constant after the coil is wound and hence a measurable loss. Hysteresis is the constant loss for a particular voltage and current.
The eddy current loss however is different for each frequency passing through the transformer.
23. What is meant by regenerative braking?
Answer: When the power supply to a running motor is cut off, it continues to run due to inertia. To stop it quickly, we place a load (resistor) across the armature winding and the motor must have maintained a continuous field supply. Thus, the back EMF voltage is applied across the resistor and due to the load, the motor stops quickly. This type of braking is called “regenerative braking”.
24. Why does a DC motor have a high beginning current?
The voltage equation for DC motors is V=Eb-IaRa, where V stands for terminal voltage, Eb for the motor's back emf, Ia for armature current, and Ra for armature resistance.Eb starts off at zero. Consequently, V=IaRa, Ia= V/Ra, where Ra is extremely small—about 0.01 ohm.That is, Ia will significantly grow.
25. What are the benefits of using an induction motor with a star-delta starter?
The response is (1). The decrease of current during motor starting is the primary benefit of utilizing a star delta starter. Three to four times the direct online starting current is used as the starting current.(2). As a result, when a motor is started in a system, the starting current and voltage dips are decreased.
26. Why Delta Star Transformers are used for Lighting Loads?
Answer: The secondary winding for a lighting load must be star wound since a neutral conductor is required. As a result, the lighting load is always imbalanced in all three phases. We use delta winding in the primary in order to reduce current imbalance. For lighting loads, a delta/star transformer is therefore utilized.
27. Why is the earth pin on a three-pin plug longer and thicker than the other pins?
The answer is dependent on the formula R=rho l/a, where area (a) and resistance (R) are inversely related. Hence, if (a) increases, R drops, and if R is less, the leakage current will follow a low resistance path, necessitating a thicker earth pin. It takes longer since the earth pin should connect first and detach last. This assures Safety for the person who uses the electrical instrument.
28. Why series motor cannot be started on no-load?
Answer: Series motor cannot be started without load because of high starting torque. Series motor are used in Trains, Crane etc.
29. Why ELCB cannot work if the N input of ELCB is not connected to earth?
Answer: ELCB is used to detect earth leakage fault. Once the phase and neutral are connected in an ELCB, the current will flow through the phase and this current will have to return to the neutral, so the resultant current is zero. Once there is an earth fault on the load side, the current from the phase will flow directly through the earth and will not return through the neutral via the ELCB. This means that once the side current passes and does not return and hence because of this current difference, the ELCB will trip and protect the other circuits from faulty loads. If the neutral is not earthed, the fault current will definitely be high and this complete fault current will return through the ELCB, and there will be no current difference.
30. How does an A.C. generator produce electricity?
In order to generate electricity, a prime mover is required. This can be either a steam turbine or a hydro turbine, which provides mechanical power input to the alternator. Due to a polarity change in the rotor poles (i.e., N-S-N-S), voltage is generated and has a sinusoidal waveform as the rotor poles move beneath the armature conductors that are mounted on the stator.
31. Why does an AC solenoid valve draw in the plunger even when the terminals are switched? Will the poles shift?
Yes, since the poles of an AC voltage change every half-cycle, the polarity of the voltage also continually changes every half-cycle. Therefore, switching out the terminals in an AC system does not result in any difference. Because of this, even though the AC solenoid's terminals are switched, it still attracts the plunger.
32. What is derating? Why it is necessary, it is same for all means for drives, motors, and cables
Derating is therefore a recommended protective measure for electronic components and devices to protect them from high temperatures and prevent failures.
33. Automatic Voltage Regulator (AVR): What is it?
The acronym for automatic voltage regulator is AVR. It is a crucial component of synchronous generators since it regulates the generator's excitation current, which in turn controls the output voltage. As a result, it has control over the generator's reactive power output.
34. What is the purpose of an exciter?
The answer is that exciters come in two varieties: rotary and static. The exciter's function is to provide the generator's fixed poles with an excitation DC voltage. A second tiny generator installed on the main generator's shaft is called a rotary exciter. If the generator is DC, it will use a slip ring and brushes to provide DC power to the rotor poles (traditional alternator). If the exciter is ac, its output is rectified by turning diodes, which then supplies DC to the main fixed poles.ac exciter is the ac generator whose field winding are stationary and armature rotates. Remaining magnetism builds up the initial voltage. It provides the generator with its starting torque.
35. What distinguishes a three-point starter from a four-point starter?
The disadvantage of the three point stater is that the shunt connection is connected to the line in a four point stater, whereas with a three point stater it is provided separately from the line.
36. Why should a high transmission system use a VCB? Why is it not possible to use ACB?
The fact that the die electric strengths in VCB are equivalent to eight times those of air means that vacuum actually has higher arc quenching properties than air. That is, air is used in LT and vacuum is used in HT breakers.
37. What distinguishes a lightning arrestor from a surge arrestor?
The lightning effect is grounded when a lightning arrestor is installed outside, but the energy is used and the effect of the surge is neutralized when a surge arrestor is installed inside panels made of resistors.
38. What is the purpose of using synchro generators to produce electricity?
In response, synchronous machines can operate at varying power factors—that is, different hypothetical POWs—by altering the field emf. Hence syn. generators r employed for the production of electricity.
39. Enlist types of dc generator?
Answer: D.C. Generators are classified into two types
- Separately excited d.c.generator
- Self-excited d.c.generator, which is further classified into; 1) series 2) shunt and
- Compound (which is further classified into cumulative and differential).
40. What is the difference between synchronous generator & asynchronous generator?
Simply put, an asynchronous generator (induction generator) simply supplies active power while monitoring reactive power for magnetizing. In contrast, a synchronous generator supplies both active and reactive power. In windmills, this kind of generator is utilized.
41. What are the two fundamental DC shunt motor speed control schemes?
Answer:
1. By employing the flux control approach, which involves connecting a rheostat across the field winding in order to regulate the field current.Because speed and flux are inversely related, it is possible to regulate speed by varying the current generated by the field winding.
2. Armature control method: in this approach, the armature winding is connected to a rheostat, and the resistance is adjusted to alter the resistive drop (IaRa). Since the speed is directly proportional to the difference between Eb and IaRa, the speed can be adjusted.
42. What is the motor's principle?
To induce a turning or twisting action, a current-carrying conductor placed in a magnetic field is said to produce torque.
43. What does the term "armature reaction" mean?
The term "armature reaction" refers to the impact of armature flu on main flux. The main flux may be opposed by the armature flux, or it may assist it.
44. What is the value of the Polarization Index? (Pi value) and polarization index defined in simple terms?
The ratio of insulation resistance (IR), or the meggar value for ten minutes, to insulation resistance for one minute is the answer. For new motors, it typically ranges between 5-7, and a well-maintained motor should typically have a value greater than 2.5. The Polarization Index Examination (PI) - The PI test calculates the insulation's capacity to withstand voltage over time. This provides a measure of the total insulation quality of the transformer's individual insulation parts. This examination is typically conducted in tandem with the Meggar Test. The ratio of insulation resistance (IR) for ten minutes to insulation resistance for one minute is used to measure it.
45. What happens if power factor leads the way in power distribution?
In the event when the power factor is near to one, or high power factor:
1. Heat-related losses will be minimized.
2. Cable becomes much more affordable and lightweight; 3. It also lessens transformer overheating.
46. Describe a two-phase motor.
A motor that has a phase split between its running and starting windings is referred to as a two-phase motor. such as an AC servo motor. where there is a 90-degree phase divergence between the control and auxiliary windings.
47. Why should EOT cranes use vvvf drives instead of non-vvvf drives?
1. Smooth beginning and ending.
2. No load jerking.
3. Precise orientation
4. Improved motor protection.
5. Adjustable speed, high and low.
6. Break shoe dependability.
7. Controlling breaks using programming.
8. Simple circuitry
9. A decrease in controls
10. Prolongs the life of the motor
48. Why is vector grouping important in power transformers?
The manufacturer lists the vector group for each power transformer. In essence, it provides information on the phase difference between the voltage and current as well as the windings' connection type (delta or wye). Delta primary, Wye secondary, and current at 11 o'clock with respect to voltage are denoted by the code EG. DYN11.
49. What kind of A.C. motor powers the fans found in homes, such as the exhaust, pedestal, ceiling, and bracket fans?
The answer is that it's a single-phase induction motor with a capacitor start and capacitor run, primarily for squirrel cage rotors.
50. Why, when birds sit on transmission lines or current wires doesn’t get shock?
It is true that birds won't receive an electrical shock if they contact the single line (phase or neutral). Birds experience electrical shocks when they come into contact with two lines, which closes the circuit. Therefore, if a person touches a single line (phase) while in the air (not touching) or while standing on the ground, he will not be shocked; however, if he touches a line (phase) while standing on the ground, he will be shocked because the ground is like a line (ground bed, or neutral), and in the majority of electric lines, the neutral is grounded. This implies that a person touching the line closes the phase-to-neutral circuit.
51. What occurs if we feed a tube light with a 220 volt DC supply?
In response, AC bulbs and other equipment are made to function by providing a high impedance to the AC supply. They typically have little resistance. Low resistance in the lamp causes the current to flow through it at a high enough level to potentially harm the bulb element when a DC supply is provided.
52. Which type of motor—a DC, induction, or synchronous motor—has a higher starting torque and starting current?
The DC Series motor offers a high torque at startup. when the DC series motor can be started without a load, the Induction and Synchronous motors cannot be started when under load.
53. What is a circuit breaker with a vacuum? Describe where we use it and with what cause.
In order to break a circuit, a breaker is typically utilized. Separating the contact terminals is what will happen when the circuit is broken. Between the terminals, an air gap forms at the moment of separation. The arc is caused by the ionization of the air in the gap caused by the current flow. This arc is quenched in the appropriate CBs using a variety of media. However, vacuum gas is the medium in VCB. The arc creation is stopped because of the vacuum pressure in the CB's air. Up to 11 kv can be used with VCBs.
54. Where is ACSR cable used and what does it mean?
In transmission and distribution, aluminum conductor steel reinforced, or ACSR, is the answer.
55. Describe the Marx Circuit.
In order to charge several capacitors in parallel and discharge them in series, it is utilized with generators. When the voltage needed for testing is greater than what is available, it is used.
56. What is the motor's principle?
To induce a turning or twisting action, a current-carrying conductor placed in a magnetic field is said to produce torque.
57. Explain electric traction to me.
The term "traction" refers to the use of electric power for traction systems, such as those used in trolleys, trains, and trams. Using electricity for all of these is known as electric traction. These days, bullet trains also employ magnetic traction. In general, electric traction systems use DC motors.
58. How can a 40w tube light be turned on with 230v AC/DC without a choke or coil?
Answer: Electronic choke makes it feasible. The particles in the tube cannot be ionized otherwise. Normal voltage and light.
In electrical engineering, what does "pu" mean?
In a power system single line diagram, the term "pu" (per unit) refers to a unit of measurement that is used to represent a large electrical circuit made up of variously rated generators, transformers, and loads (measured in MVA and KV). We employ the Pu idea to unify all the ratings into a single platform. Generally speaking, the component with the highest MVA and KV ratings is deemed to have the base values; all other component ratings are then reverted to this basis. We refer to those values as pu values. True value minus base value is p.u.
59. Operation carried out in Thermal power station?
Answer: The water is obtained in the boiler and the coal is burnt so that steam is obtained this steam is allowed to hit the turbine, the turbine which is coupled with the generator generates the electricity.
60. Why is a fuse in the phase of an AC circuit and a link in the neutral?
The link is given in a link form to resist large amps since it is placed at a neutral common point in the circuit from which different connections are obtained for the separate control circuit. However, the fuse in the AC circuit's phase is made in such a way that the fuse rating is solely determined for that specific circuit, or the load. Therefore, in the event of a malfunction, the fuse associated with that specific control circuit alone will blow.
61. Enlist types of dc generator?
Answer: D.C. Generators are classified into two types :
- 1)separately excited d.c.generator
- 2)selfexcited d.c.generator,
which is further classified into;
- 1)series
- 2)shunt and
- 3)compound (which is further classified into cumulative and differential).
62. What distinguishes an electronic fan regulator from a standard rheostat regulator?
In an electronic regulator, power losses are lower as the speed is decreased because the electronic regulator provides the necessary power for that specific speed; in an ordinary regulator, on the other hand, power is wasted at all speeds and no power is saved. Speed control in an electronic regulator is achieved by adjusting the firing angle using a triac; with a rheostat, speed control is achieved by gradually decreasing the resistance.
63. How were electrical and electronics engineering different from one another?
The study and use of electricity, electronics, and electromagnetic are the main areas of research and application for the engineering discipline of electrical engineering. Electronic engineering, also known as electronics design, is the branch of engineering that designs electronic circuits, devices, and systems. Typically, printed circuit boards are the basis for these designs, which also include passive electrical components and non-linear and active electrical components like electron tubes and semiconductor devices, particularly transistors, diodes, and integrated circuits.
64. What is the function of an exciter?
The answer is that exciters come in two varieties: rotary and static. The exciter's function is to provide the generator's fixed poles with an excitation DC voltage. A second tiny generator installed on the main generator's shaft is called a rotary exciter. If the generator is DC, it will use a slip ring and brushes to provide DC power to the rotor poles (traditional alternator). If the exciter is ac, its output is rectified by turning diodes, which then supplies DC to the main fixed poles.The ac exciter is a type of ac generator that has rotating armature and stationary field windings. Remaining magnetism builds up the initial voltage. It provides the generator with its starting torque.
65. What does BOM mean?
Bill of Materials, or BOM for short, is an inventory of the components that go into making up a product assembly. For instance, a lawnmower needs assemblies for the handle, metal deck, engine, control, and blades.
66. Describe what a QMS is.
The Quality Management System, or QMS for short, records all the data required for the organization's operational controls and design, including issue reporting, monitoring, training, and continuous improvement to ensure that the business produces a consistent product.
67. What is the difficulty in producing goods?
Creating more efficient production processes, securing the best possible material and component sources at the lowest possible cost, cutting production times, getting rid of waste, and maintaining product quality are the primary challenges in manufacturing.
68. What does "factory overhead" mean?
Everything that costs money throughout the production process is called "factory overhead," which does not include the price of raw materials or direct labor.
69. Describe the process of overseeing a manufacturing facility.
The many stages of production must be attended to when supervising a manufacturing process. The factory supervisor should also keep a careful check on the inventory before it is used.
- First step: Maintain documentation of the various stages of production and determine whether the crew's output is sufficient to meet demand.
- Step 2: Locate any bottlenecks inside the unit and take steps to remove them
- Step 3: Monitor inventories and make an effort to use less liquid capital after unused material
- Step 4: Check to see if the finished products live up to the company's quality requirements.
70. What are interpoles and why are they required in a DC machine?
Answer: Interpoles, also known as commutating poles, are additional field poles located between the main poles of a DC machine. They are series-excited by the armature current and are positioned such that they influence the armature coils only during the commutation process. Interpoles help to induce an additional EMF in the coil undergoing commutation, which opposes the self-induced EMF and aids in smooth current reversal. This helps to prevent sparking at the brushes and improve the overall performance of the DC machine.
71. Comment on the working principle of operation of a single-phase transformer.
Answer: A single-phase transformer operates based on the principle of electromagnetic induction. When an alternating current (AC) is applied to the primary winding, it creates a time-varying magnetic flux. This flux is linked with both the primary and secondary windings.
According to Faraday's Law of Electromagnetic Induction, the changing magnetic flux induces an electromotive force (EMF) in both windings. The EMF induced in the primary winding is known as the self-induced EMF and opposes the applied voltage (due to Lenz's Law). This is also referred to as the back EMF.
The EMF induced in the secondary winding is known as the mutually induced EMF. When a load is connected to the secondary winding, a current flows through it. This secondary current creates a secondary magnetic flux that opposes the primary flux. This opposition reduces the primary current, effectively transforming the voltage from the primary to the secondary winding.
In essence, a transformer works by transferring electrical energy from the primary side to the secondary side through electromagnetic induction, with the voltage ratio between the two windings being determined by the ratio of their turns.
72. What is the speed rating?
The motor's speed is referred to as its rated speed at the moment it is drawing its usual current, or rated current. It is the pace at which a system can operate with little current and greatest efficiency.
73. Will a bulb glow if it is connected to two phases?
The light will glow if the voltage differential between the two phases is equal to the voltage of the lamp.
Depending on the type of lamp, a large voltage differential will cause damage, whilst a lesser voltage difference will cause the lamp to glow.
74. What does KVAR stand for in full?
We are aware that there are three different kinds of power in electronics: apparent, reactive, and active. Kilo Volt Amps with Reactive Component is what KVAR stands for.
75. Out of two 100w and 40w bulbs linked in series across a 230v supply, which one will put out the most light and why?
Given that two bulbs are connected in series, they will receive an equivalent quantity of electricity, but the supply voltage across each bulb will remain constant (P=V^2/R).Therefore, a 40W bulb will glow brighter since it has a higher resistance and a higher voltage across it (V=IR).
76. Why do bus bars and isolators conduct temperature rise?
Since bus bars and isolators are designed to withstand continuous power flow, high currents will cause them to heat up. Testing these devices for temperature rise is therefore essential.
77. System: What Is It?
The collection of components that together make up a system are those that are linked in a certain order to carry out a particular purpose.
78. What is the Control System?
When input and output are connected in a way that makes it possible for the input quantity to control the output quantity or variable, the system is referred to as a control system.
Command signal or excitation is the name of the input quantity, and regulated variable or response is the name of the output quantity.
79. What kinds of control systems are there?
There are two main categories of control systems:
- Open loop Control System
- Control Systems with Closed Loops
Systems of control known as "open loops" are those in which the quantity of the output has no bearing on the quantity of the input. There isn't any feedback for rectification from the output quantity to the input quantity.
Closed Loop Control System: A closed loop control system maintains the system's intended output by providing feedback from the output quantity to the input amount for correction.
80. What does a control system feedback mean?
The control system's feedback mechanism involves sampling the output and feeding a proportionate signal back to the input to automatically fix errors (i.e., any changes to the desired output) and then processing the data further to obtain the desired output once more.
81. Why the Control System Prefers Negative Feedback?
In a control system, feedback's job is to return the sampled output to the input and check for errors (disturbances from the intended outcome) by comparing the output signal with the input signal.
The system is more stable when there is negative feedback because it rejects any disturbance signals and is less susceptible to changes in the parameters. Therefore, negative feedback is taken into account in control systems.
82. How does positive feedback affect the system's stability?
Since positive feedback raises the error signal and causes instability in the system, it is often not used in control systems. However, some internal signals and parameters are amplified in small loop control systems through the application of positive feedbacks.
83. What is a relay for protection?
In the event of an anomalous state or a malfunction, the electrical device is intended to trigger the isolation of a specific section of the electrical infrastructure or to sound an alarm. Relays, to put it simply, are electrical devices that, upon detecting a problem, send a signal to an isolation device (such as a circuit breaker) to assist in isolating the defective system from the intact electrical system.
84. What kinds of relays are used to safeguard machinery and transmission lines?
The following relay types are typically used to protect transmission lines:
- undervoltage, underfrequency, distance, directional, overcurrent, and directional relays.
- Pilot relays, phase sequence relays, thermal relays, and differential relays.
85. How is the protection of the electrical power system divided?
The protection of the transmission lines, feeders, bus bars, transformers, generators, and feeders make up the total system protection.
86. How are the relays in the electricity system connected?
The current transformer (CT) or potential transformer (PT) is how the relays are connected to the electrical system.
87. What kinds of electromechanical relay operating principles are there?
Eletro-mechanical relays function according to two principles. two types of electromagnetic fields: induction and attraction. Relay plungers are drawn to solenoids or armatures are drawn to the electromagnet's poles in electromagnetic attraction. The electro-magnetic induction motor operates on a similar basis to that of an induction motor. The electromagnetic induction concept generates torque.
88. What do the circuit breaker and relay do in the event of a fault?
Relay activates and closes the trip coils once it detects a fault state. This will cause the circuit breaker to activate and open the contacts.
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