Engineering Talk:Electrical Engineering Forum

MCQ Test V on Electric Drive and Speed Control

2021-06-30T08:47:00.011-04:00

Objective Test on Electric Drive and Speed Control

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MCQ Test on Power Semiconductor Device

2021-06-16T12:46:00.018-04:00

Objective Test on Power Semiconductor Device

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MCQ Test on Three phase Synchronous motor

2021-05-27T11:24:00.012-04:00

Objective Test on Three phase Synchronous motor

Syllabus for the test:-Principle of operation. Methods of starting. Pull-in and pull-out torques. Equivalent circuit, significance of torque angle and torque equation. Losses, efficiency and Power flow chart. Operation of 3-phase Synchronous motor with constant excitation and variable load. Operation with constant load and variable excitation (‘V’ Curves and ‘inverted V’ curves).Applications of 3-ph synchronous motors.

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Three Phase Induction motor working Principle and its Types

2021-04-17T12:39:00.050-04:00

Three Phase Induction motor

Electrical motor converts electrical energy into mechanical energy.

What are the types of motors?

Based on Supply Motor are basically two types: AC and DC Motor. AC motor are divided into two types :Induction motor(Speed is variable), induction motor are also known as asynchronous motor and Synchronous motor(speed is constant ).

What are the types of induction motors?

Depending upon nature of AC supply induction motor are two types (a)Single phase induction motor and (b) 3 Phase Induction motor. Here we will discuss in detail about three phase induction motor.

Click Here to Download 3 Phase induction Motor .ppt

General aspects

•The construction of induction motor and induction generator are same.

•Induction motors are popularly used in the industry.

•Main features: cheap and low maintenance.

•Main disadvantages: speed control is not easy.

Overview of Three-Phase Induction Motor

•Induction motors are used in many industrial, residential, commercial and utility applications.

•Induction Motors transform electrical energy into mechanical energy.

•It is used for pump or fan, or connected to some other form such as a conveyor, winder, or mixer.

Application of IM

3 phase induction motors takes three phase supply from mains and used for various industrial applications because of their following advantages -

1. Three phase Induction motors are very simple and rugged construction.

2. It is are very reliable, robust and having low cost.

3. The efficiency of 3 phase IM is high and its power factor is good at full load.

4. It required minimum maintenance.

4. Three phase induction motor is self starting hence extra mechanism is not required for starting.

They also have some disadvantages-

1. The Speed of induction motor decreases with increase in load, same as a DC shunt motor.

2. If speed is to be varied, the efficiency may change.

Construction

•The three basic parts of induction motor are the rotor, stator, and enclosure.

•The stator is stationary part while rotor is rotating part of induction motor.

•The enclosure protects the stator and rotor of the motor from harmful effects of the environment in which the motor operates.

Bearings which is mounted on the shaft, support the rotor . A fan, also mounted on the shaft, which is used for cooling purpose.

Construction of Induction motor

Construction of Stator

•The stator winding is wounded on stator core which is made up of several thin laminations.

Coils of insulated wire are inserted into stator slots of the stator core. The stator winding either connected in delta or star configuration. The stator windings of induction motor are connected to the supply mains.

Construction of Rotor

•The rotor is the rotating part of three phase induction motor.

•It can be found in two types:

–Squirrel cage

–Wound rotor

What are the types of 3-phase induction motors?

Three phase Induction motor types : Based on rotor construction three phase Induction motor are two types-

Squirrel cage induction motor:

Rotor winding is composed of rotor copper bars embedded in the rotor slots and their end terminal is shorted end rings arrangements. It is very Simple, low cost, robust and has low maintenance.

Wound rotor or slip ring induction motor:

Rotor winding is wound by wires. The rotor winding terminals can be connected to external resistance through slip rings and brushes for smooth speed control.

•However, the most common type of rotor is the “squirrel cage” rotor.

Types of Motor

Difference between Three phase Squirrel cage induction motor and Wound Rotor induction motor:

Squirrel cage rotor

1 No Slip rings or brushes

2 External resistance can not be connected.

3 Starting torque can not be adjusted.

4 Less rotor copper loss.

5 Higher efficiency

6 Applications includes lathes , fan ,water pumps

Wound rotor or Slip ring rotor :

1 Slip rings or brushes are used

2 External resistance can be connected.

3 Starting torque can be adjusted.

4 High rotor copper loss.

5 Low efficiency.

6 Applications includes crane ,elevators ,compressors , lifts etc.

Working principle of three phase induction motor

•When a thee phase stator winding is connected to a three phase voltage supply, 3 phase current will flow in the stator winding, which will produces 3 phase flux in the stator.

The nature of this flux is rotating with constant speed and fixed amplitude. The rotating magnetic flux will rotate at a speed called as Synchronous Speed, Ns and which is given as Ns=120 f/p

Where; Ns=Synchronous speed: speed of rotating flux, p = is the number of poles, and f = the frequency of supply

How 3 phase induction motor starts :Torque producing mechanism

When a 3 phase stator winding is connected to a three phase voltage supply, 3 phase current will flow in the windings, hence the stator is energized which produces rotating magnetic flux .

A rotating flux Φ is produced which links with rotor and according to faradays law of electromagnetic induction principle a voltage is induces in the rotor winding (like a transformer).

The induced voltage produces rotor current. The rotor current interacts with the flux and as we know that current carrying conductor placed in magnetic field it experiences torque.

This current will flow in such a direction that the rotor will experience a force that accelerates it in the same direction as that of RMF.

Slip and Rotor Speed

What is slip in induction motor?

Slip (s): The rotor speed of an Induction machine is different from the speed of Rotating magnetic field. The percentage difference between synchronous speed and rotor speed is called as slip.

s=(Ns-Nr)/Ns or Nr= Ns(1-s)

Where; ns = synchronous speed (rpm), Nr = mechanical speed of rotor (rpm)

Under normal operating conditions, slip lies between 1% -5%, which is very small.

Rotor Speed : When the rotor rotates with a speed of Nr (rps), the stator flux will circulate the rotor conductor at a speed of (Ns-Nr) rps. Hence, the frequency of the rotor can be derived as:

Where; s = slip, f = supply frequency

Torque Equation-The torque produced by IM depends on :

1.The rotor Power factor under running condition= CosØ 2

2.The rotor current under running condition= I2r

3.The Part of rotating magnetic field which induces e.m.f in rotor winding= Ø

Therefore, T α Ø Ir CosØ 2 ----------------(i)

But Ø α E1 Where E1 = Stator voltage But E1/E2 =K= Transformation ratio

Therefore, E2 α E1 Hence, E2 α Ø and E2 = Er

Equivalent circuit

•Here, k=3/2πNs Ns = Synchronous speed in RPS= Ns/60

This expression indicates that:

1.For a slip ring IM we can connect external resistance by modifying R2 in the rotor circuit.

2.Hence we can adjust Starting torque by varying rotor resistance R2.

3.Modification of R2 in Cage type IM is not possible.

Relation between Air gap power(Pg),Rotor copper loss (Pcu) and Mechanical Power output(Pm) :

Power flow diagram

a).Relation between Pg and Pcu:

Pg= Air gap Power

Pcu= Rotor copper loss

Pm= Mechanical Power

Let, Ns= synchronous speed and Nr= Rotor Speed

As we know, P= ω T (Angular Freq x Torque)

Pg = ω Tg

Pg = 2πNsTg -------------------(1)

Similarly, Pm= 2πNrTg ------(2)

Pcu = Pg-Pm

Pcu = 2πNsTg - 2πNrTg

Pcu = 2πTg (Ns – Nr) -------------(3)

Dividing equation 1 and 3

Therefore Pcu = sPg --------------(4)

b.Relation between Pm and Pcu:

Pg= Pm + Pcu

Pcu(1/s) = Pm + Pcu

Pcu = sPm + sPcu

Pcu – sPcu = sPm

Pcu(1-s) = sPm

Therefore Pcu/Pm = (s/(1-s) ---------(5)

Comparing Pcu = sPg -----------------(4) and (5)

Pg : Pcu : Pm = 1 : S : (1-S)

Need of Starter for three phase Induction motor: 3 Phase IM is self starting, because there is a starting torque.

•Let V1 be the stator voltage /phase

•Ze1 be the equivalent impedance/ phase ref to stator.

Ist = V1/ Ze1

•At the time of starting Ze1 is very very small, hence short circuit current Isc is very high. Generally it is 5 times greater that full load current.

•This higher current in stator winding may damage the winding due to overheating. Hence at the time of starting starters are required in three phase induction motor.

Types of Starters

Starters for Squirrel cage rotor induction motors

i) Direct on line (D.O.L.) starter

ii) Stator – resistance starter

iii) Auto transformer starter

iv) Star delta starter

Starters for Slip Ring Induction Motor

i) Rotor resistance starter

Speed control of Three phase induction motor

MCQ Test-01 on DC Machines

2021-04-15T12:45:00.004-04:00

Objective Test on DC Machines

Syllabus: Construction, working principle of D.C. generator, emf equation of D. C. generator, working principle of D.C. motor, types of D.C. motor, back emf, torque equation for D.C. motor, characteristics of D.C. motor (series and shunt only), three-point starter for D.C shunt motor, methods for speed control of D.C. shunt and series motors, industrial applications. Special purpose motors: Construction, working principle, characteristic and applications of stepper motors, A.C. and D.C servomotors, universal motors, brushless DC motors.

Guidelines for MCQ Test-01

There are Approx. 20 questions of total 20marks
Each question carry 01 marks
Total duration of the test is 25 Minutes.
Types of questions will be numerical/theoretical having multiple choice, fill in the blanks, Multiple correct option, match the following types.
Some Question having more than one correct option ,so tick all correct answers carefully.
There is no negative marking.

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MCQ Test on Transducer

2021-02-21T00:22:00.002-05:00

Objective Test on Transducer:

Syllabus of TRANSDUCERS: Classification, Selection criteria, Sources of error for parameter under measurement, Transducer specifications, Temperature transducer, Linear variable differential transducer, Strain gauge. Various applications of transducers.

Transducer

Guidelines for MCQ Test

• There are 20 questions of total 20marks

• Each question carry 01 marks

• Total duration of the test is 1hour.

• Types of questions will be numerical/theoretical having multiple choice, fill in the blanks, Multiple correct option, match the following types.

• Some Question having more than one correct option ,so tick all correct answers.

• There is no negative marking.

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MCQ Test on Digital Electronics

2021-02-04T03:13:00.005-05:00

Objective Test on Digital Electronics:

MCQ Test on Digital Electronics

Topics: Introduction, digital signals, Basic logic gates and universal gates: AND, OR, NOR, NOT, NAND, EX-OR, EX-NOR, Boolean laws, Arithmetic circuits: Half Adder, Full Adder, Flip flops: Basic latch, Gated SR, JK flip flop, D flip flop, T flip flop, Introduction to Shift registers and Counters.

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MCQ Test on Diode and Diode circuits

2021-01-05T04:42:00.015-05:00

Objective test on Diode and Diode circuits.

PN Junction diode: characteristic and analysis, Types of diodes – Zener diodes, Photodiodes, Light emitting diodes (LED’s), Rectifiers: Half wave, Full wave and Bridge rectifier circuits and their analysis, BJT, types, construction, configurations and characteristics.

Diode and Diode circuits

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Objective practice test on Diode and Diode circuits

2021-01-04T10:01:00.004-05:00

Objective test: Diode and Diode circuits.

Objective test on Diode and Diode circuits.

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Questions on Basics of Electronics and Transducer

2021-01-01T03:04:00.004-05:00

Diode and Diode Circuit

1) What do you mean by dc load line of a transistor? What is meant by Q point?
2) What is need of biasing a transistor?
3) Describe fixed biased, collector to base bias and voltage divider bias circuits with circuit diagram.
4) Draw and describe input and output characteristics of BJT? What is Early effect in BJT?
5) Differentiate between CB, CE and CC configurations.
6) Sketch the CE output characteristics and indicate the active, saturation and cut-off regions.
7) Explain BJT as a switch. Why CB and CC configurations are not preferred.
8) Explain input output characteristics of CE amplifier.
9) Explain working of transistor as a switch
10) Explain how EX-OR gate can be used as an invertor.
11) Draw and describe working of bridge rectifier and derive equations for V_DC, V_RMS, I_DC & I_RMS. Also draw input and output voltage waveforms.
12) Draw and describe working of full wave center tap rectifier and derive equations for V_DC, V_RMS, I_DC,& I_RMS, TUF, FF & rectification efficiency. Also draw input and output voltage waveforms
13) Draw and describe construction, working of zener diode, tunnel diode, varactor diode.
14) Draw and describe circuit diagram of zener diode as a shunt voltage regulator.
15) Input=5V_RMS, Diodes=silicon diodes, load resistor=2.2 KΩ, calculate, V_DC, V_RMS, I_DC & I_RMS, TUF, FF, & rectification efficiency.
16) What is difference between tunnel diode and PN diode?
17) What are different applications of varactor diode?
18) Write PN diode current equation and describe reverse saturation current.
19) Draw waveforms for output voltage, diode voltage, diode current and input voltage of bridge rectifier circuit. Assume silicon diodes.
20) Design and draw Zener shunt regulator circuit to meet following specifications- VL=8V, Vin=30V, IL=50mA, Izmin=5mA, Pz=1 Watt. Calculate RLmin, RLmax, & R.
21) Half wave rectifier has turns ratio 4:1 with input 240V, 50 Hz supply, Forward resistance of diode (R_F)=10Ω, secondary resistance(R_S)= 80Ω and load resistance (R_L)=1KΩ. Calculate V_DC, V_RMS, I_DC & I_RMSand rectification efficiency.
22) Full wave centre tapped rectifier has turns ratio 2:1 with input 230V, 50 Hz supply, Forward resistance of diode (R_F)=1Ω, secondary resistance(R_S)= 50Ω and load resistance (R_L)=2KΩ. Calculate V_DC, V_RMS, I_DC & I_RMSand rectification efficiency.
23) Bridge rectifier has turns ratio 4:1 with input 230V, 50 Hz supply, Forward resistance of diode (R_F)=1Ω, secondary resistance(R_S)= 40Ω and load resistance (R_L)=3KΩ. Calculate V_DC, V_RMS, I_DC & I_RMSand rectification efficiency.

Question Bank on Basic Electronics

Digital Electronics

1) Solve using Boolean laws, theorems,

a. (AB)’+(A+B)’+AB’

b. AC+C(A+A’B)

c. AB+ABC+AB(E+F)

2) Implement combinational logic for ExOR gate

3) Implement 2:1 mux using NAND gates

4) Implement following circuits using NOR gates 2:4 decoder, 2:1 Multiplexer

5) Draw and describe SR latch using NAND gates

6) Describe JK flip-flop using its state table

7) What are advantages of JK master slave flip-flop? Describe racing in JK flip-flop?

8) Design 2:4 decoder and describe operation.

9) Draw and describe 4 bit asynchronous counter

10) Draw and describe 4 bit shift register in SISO, SIPO, PISO, PIPO modes. Also draw waveforms.

11) Describe single bit half adder and full adder.

12) Draw and explain full adder using two half adder with its truth table

13) Explain the operation of multiplexer and Demultiplexer.

14) Explain the UP/Down counter using J-K Flip Flop.

15) Design the Full adder logic gate using K-Map.

16) Explain and describe the K-Map.

17) Draw the schematic diagram & explain working of 4:1 mux and 1:4 demux.

18) Implement the following with minimum number of NAND gates.

i) Y=AD+CB

ii) Z=(A( ))

19 19)State and prove the de-Morgan’s theorem. Simplify the following Boolean expression: 20) Compare Microprocessor and Micro-Controller

21) Describe following Boolean laws with examples,

a. Commutative law

b. Associative law

c. Distributive law

22) Describe with example, principle of duality.

23) What do you mean by combinational logic circuits? Explain examples.

24) What do you mean by sequential logic circuits? Explain examples.

Transducer

1) Define a transducer and sensor.

2) Draw and describe block diagram of transducer.

3) Classify transducers

4) What are various selection criterions of transducer.

5) Describe possible sources of error in parameter measurement.

6) Draw and describe construction, transduction principle and working of LVDT, Ultrasonic transducer.

7) What is operating principle of flow measurement?

8) Draw and describe construction working and types of strain gauge.

9) Draw and describe block diagram of load cell.

10) What are different types of temperature transducer? Describe RTD and thermocouple in detail with diagrams.

11) Describe with diagram construction and working of elastic transducer.

12) Draw block diagram of digital thermometer and describe working.

13) Draw block diagram of weighing machine and describe operation.

14) Describe specifications, test conditions and operating conditions of transducer.

15)Draw and explain block diagram of instrumentation system.

16)Explain the Ultrasonic transducer with details.

17)Write short note of: Load cell, Flow measurement and Temperature transducer.

18)What do you mean by Electroluminescence? Describe with figure.

MCQ Test on transformer and DC Machines

2020-12-09T10:05:00.020-05:00

Objective Test 02 on basics of transformer and DC machines

Syllabus of test: ELECTRICAL MACHINES

Electromechanical energy conversion: Types of ac and dc motors, Characteristics and applications, ac generators. Single phase transformer: Construction, principle of working, emf equation, ratios, regulation, losses, efficiency, condition for maximum efficiency, Introduction to O.C & S.C. test, Introduction to auto-transformer and instrument transformer.

MCQ Test 02

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Objective Test transformer and DC Machines

2020-12-07T12:47:00.012-05:00

Objective test 01 : Transformer and DC Machines

Objective Test
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Questions on Basic Electrical DC and AC Circuits

2020-11-21T03:44:00.003-05:00

Assignment Questions: Basics of Electrical and Electronics Engineering

D.C. CIRCUITS AND A.C. CIRCUITS

State Kirchoff’s voltage law, Kirchoff’s current law
Write equations to transform electrical networks from star to delta and vice versa
What is operating principle to generate alternating voltage?
Draw & Describe the phase relation between current and voltage in RC & RL circuit?
Find current through 4ohm resistor in Fig 1 by nodal analysis .

Figure of Numerical questions

What is relation between maximum voltage, RMS voltage and average voltage of sine wave?
What do you mean by power factor and quality factor? Write their equations.
State and explain Superposition theorem in detail.
A coil having an inductance of 100 mH and resistance 20 Ω is connected in series with a 30 μF capacitor across a 300 V ac supply. Calculate (a) total current (b) voltage across resistance (c) voltage across inductor
Apply Norton’s theorem to calculate current in 5 Ω resistor in Fig 2.
State and Explain Thevenin’s theorem in detail
What do you mean by Node and Mesh analysis.
Define the terminologies:- a. Instantaneous values b. Cycle c. Periodic time d. Angular velocity e. Amplitude
Find the current through 8 Ohm resistor using loop analysis in Fig 3.
By applying Kirchhoff’s current law , Solve and find V_CE and V_{GE in}Fig 4.
What do you mean by phase and phase difference of alternating current and voltages?
Draw and describe working of series RL circuit connected across ac source with phasor diagram.
Draw and describe working of series RC circuit connected across ac source with phasor diagram.
State and explain Superposition theorem.
In the network shown in Figure 5, find the value of power dissipated across RL=5ohm.
Derive equations for average, RMS voltage, & Form Factor of sinusoidal waveform?
Draw and describe working of RLC series circuit and write current equation.
Find Impedance of Pure Resistive, Inductive and Capacitive Circuit.
State and explain Ohm’s law.
Using Thevenin’s theorem, calculate the current flowing through the 4 Ω resistor in Fig 6.
A choke coil having a resistance of 15Ω & an inductance of 63.7 mH is connected in series with a non-inductive resistor of 10Ω. The circuit has been connected across a 240V, 50 Hz mains. Calculate,
a. Current and Power factor b. Voltage across the coil c. Voltage across the non-inductive resistor
Find V1, V2, V3 and current flowing from A to D in Fig 7.
State Kirchoff’s voltage law, Kirchoff’s current law
Describe AC through Pure Resistive, Inductive and Capacitive Circuit.
What is impedance triangle and power triangle.

Network Theory Quiz

2020-11-07T05:36:00.008-05:00

Network Theory Quiz

Syllabus: Two Port Network Analysis and Filters & Attenuators.

Quiz on two port network

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MCQ Test 01 on DC and AC circuits

2020-10-30T00:20:00.007-04:00

MCQ Test-01

Syllabus of MCQ Test-01:D.C. CIRCUITS AND A.C. CIRCUITS :Classification of network, Ohm's law, KCL, KVL, network simplification using star-delta/delta-star transformations, mesh analysis, network theorems (Superposition and Thevenin).Generation of alternating voltages, fundamentals of ac circuits, behaviour of pure R, L, C in ac circuits, concept of phasor and its representation, series RL, RC and RLC circuits.

Basic Electrical Test Objective

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Basic Electrical Test

2020-10-13T02:17:00.003-04:00

Basic Electrical Test-01

D.C. CIRCUITS

Classification of network, Ohm's law, KCL, KVL, network simplification using star-delta / delta-star transformations, mesh analysis, network theorems (Superposition and Thevenin).

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Basics of electrical and electronics engineering

2020-09-06T12:11:00.086-04:00

Analysis of DC circuit and AC circuit:

We will cover the following topics related to basics of electrical and electronics engineering for analysis of DC and AC circuits:

Basics of electrical engineering:

•Network classification, Ohm's law, KCL, KVL

• Use star delta transformations, mesh analysis to simplify the network

• Network theorem (Superposition and Thevenin).

• Generation of AC voltage, basic principles of AC circuits

• The behavior of pure R, L, C in AC circuits, the concept and representation of phasors,

• RL, RC and RLC series circuits.

Network classification :The electric Network is the combination of circuits and electrical components (for example, batteries, resistors, inductors, capacitors, switches)

An electric circuit composed of a closed loop, which provides a return path for the current.

Linear power circuit, a special type consisting of only active element (voltage or current), linear distributed elements (transmission lines), an linear lumped elements (resistors, capacitors, inductors).

Electric network is a combination of circuits with active and passive elements.

Active components: voltage source, current source, etc.

Passive components: resistors, capacitors, inductors, etc.

Different ways to classify the network:

Active and Passive Network:

An active network is a network containing an active source, which can be a voltage or current source. It contains one or more emf source.

A passive network is a network that does not contain active sources. There is no source of emf. It contains R, L, and C elements only.

Linear and nonlinear network:

If the signal of the network follows the superposition principle, the network is linear, otherwise it is non-linear.

A linear circuit is a circuit whose output is proportional to its input. Linear circuits are subject to homogeneity (scaling) and additivity.

Scientific calculator:Casio fx-991 ES

Laptop specification(HP/DELL i5 processor, RAM-8GB,SSD-256GB,HDD-1TB,Grafics card-2GB )

Click below to download Syllabus, book pdf,ppt etc:

Basics of electrical and electronics engineering syllabus (MIT-ADTU)

Basics of electrical and electronics engineering lab manual

Basic electrical and electronics engineering pdf (book)

Basic electrical and electronics engineering multiple choice questions

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D.C. and AC Circuits ppt

Click here for Subjective Questions on Basic Electrical DC and AC Circuits(Unit-I)

Click here for objective question practice set-I (Basics of AC and DC Circuit)

Click here for objective question practice set- II (Basics of AC and DC Circuit)

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ELECTRICAL MACHINES(Motor and 1 phase Transformer) ppt

Click here for objective question practice set-I(Electrical Machines)

Click here for objective question practice set-II(Electrical Machines)

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Diode and Diode Circuits ppt(Click here)

Questions bank on Basic Electronics(Diode,BJT,Digital Electronics) and Transducer(Unit-III,IV and V)(Click here)

Click here for objective question practice set-I (Diode and Diode circuits)

Click here for objective question practice set-II (Diode and Diode circuits)

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Digital Electronics ppt(Click here)
Questions bank on Basic Electronics(Diode,BJT,Digital Electronics) and Transducer(Unit-III,IV and V)(Click here)

Click here for objective question practice set-I (Digital Electronics)

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Transducer

Questions bank on Transducer(Unit-III,IV and V)(Click here)

Click here for objective question practice set-I (Transducer)

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Ohm's Law:

This is the most basic law of electrical engineering. As long as the temperature and other physical parameters of the conductor remain unchanged, the potential difference between the two ends of the conductor is proportional to the current flowing through the conductor.

V∝I or V = RI

Here, R = the resistance of the conductor (ohm, Ω)

The unit of resistance, ohm is defined as the resistance that allows one ampere of current to flow when a potential difference of one volt is applied to the resistance.

Another way to illustrate Ohm’s law is

I = GV

The constant of proportionality is called conductor conductance.

Therefore, G = 1 / R

The graphical form of Ohm’s Law,

V-I Characteristics

Here voltage is the independent variable (cause) and current is the dependent variable (effect)

The slope of the line is the reciprocal of resistance (1 / R), which is the conductance

A conductor exhibiting linear VI characteristics has linear resistance.

The slope of the line is reciprocal of the resistance (1/R) and is conductance(G)

Resistance:

A resistor is a property of any material which always oppose the flow of current. If the current flowing through a resistor is proportional to the potential difference between both ends, the resistance of the resistor is considered linear.

If the resistance changes with the magnitude of the voltage or current, the resistance is said to be non-linear.

R ∝l/A or R =ρl/A

Where ρ=Resistivity (ohmmeter, Ωm),l =length of the material, A=Cross sectional area of the material.

Resistance: Color coding of resistance

Google image by: https://www.instructables.com/id

Combination of resistance:

Combination of resistance

1. Series combination:

In figure(a), current I flows through three resistances. Applied voltage V must be equal to the sum of the three individual voltage drops V1,V2, V3.

V =V1+V2+V3

= IR1+IR2+IR3

=I (R1+R2+R3)

V=IRs

Where Rs = R1+R2+R3

2. Parallel combination:

In figure (b), voltage V is equal to all three resistances.

I1=V/R1;I2=V/R2;I3=V/R3

Here, I = I1+I2+I3

= V(1/R1+1/R2+1/R3)

= V/Rp

1/Rp=(1/R1+1/R2+1/R3)

For two resistances,

1/Rp=1/R1+1/R2=R1R2/(R1+R2)

Voltage Divider Rule:

Voltage division takes place in series circuit.The concept of voltage divider is very useful when analyzing the circuits.

Consider the circuit in which two resistors R1 and R2 are connected in series with a voltage source V. The current I is given as:

I = V /(R1 + R2)

Therefore, the voltage V1 across resistor R1 is

V1 = IR1 = V R1 /(R1 + R2)

Similarly, the voltage V2 across resistor R2 is given as:

V2 = IR2 = V R2 /(R1 + R2)

Current divider rules:

Let us consider that two resistors (R1 and R2) are connected in parallel. Therefore, a voltage V appears at both resistor.

V = I1R1 and V = I2R2

Among them, I2 = V / R2 = I1 R1 / R2

I = I1 + I2 = I1 + I1 R1 / R2 = I1 [R1 + R2 / R2]

I1 = IR2 / R1R2

The current through R2 is given as

I2 = IR1 / R1R2

Kirchhoff's Law

The German physicist Gustav Kirchhoff (Gustav Kirchhoff) observed that these are specific examples of analyzing two basic conditions of any power circuit. The possible conditions are as follows:

The first Kirchhoff ‘s law is current law(KCL): at any moment, the algebraic sum of the current at the network node is zero.

At any electrical junction incoming current is equal to outgoing current. Different sign positive and negative are assigned to keep the current flowing to and away from the junction.

Kirchhoff ‘s current law

The second Kirchhoff ‘s voltage law: In any case in a closed loop, the algebraic sum of e.m.f that works in the loop is equal to the algebraic sum of potential drop in the loop.

KVL

V=V1+V2+V3

Circuit Theorems

Superposition Theorem
Thevenin's Theorem
Norton's Theorem
Maximum Power Transfer

Superposition Theorem:

In any linear, bilateral network having various active and passive element, the response (current, voltage) across any passive element is algebraic sum of all the responses across that element when considering one source at a time and deactivation all other source at that instant.

Because the circuit is linear, we can find the circuit's response to each source acting alone, and then add them together to find the circuit's response to all sources acting together. This is the so-called superposition theorem.

The principle of superposition states that the voltage across a component (or the current flowing through it) in a linear circuit is the algebraic sum of the voltage across the component (or the current flowing through it). This is due to the fact that each independent power supply works independently. .

Steps to apply the superposition principle:

1. Turn off all independent sources except one. Look for the response (voltage or current) due to a valid source.

2. Repeat step 1 for each other independent source.

3. Find the total output by adding all the results found in steps 1 and 2 above algebraically.

Let us take one example :

#Remedial Lecture-01:Solve 2 Question(Given below) on Basic Law's of Electrical Network & Paste your photo of your solution by Clicking on plus(+)pink sign below.Write your roll no and name on every page of your solution then take photo.

#Remedial Lecture-02: Solve 3 Question(Given below) on Basic Law's of Electrical Network & upload your scanned/photo of your solution .Write your roll no and name on every page of your solution then take photo.

Click here to see the question.

#Remedial Lecture-03 & 04 : Solve Questions (Given below) on Basic Law's of Electrical Network.

Click here to see the question.

MCQ Test-01Click here for MCQ Test-01. Syllabus of MCQ Test-01:D.C. CIRCUITS AND A.C. CIRCUITS: Classification of network, Ohm's law, KCL, KVL, network simplification using star-delta / delta-star transformations, mesh analysis, network theorems (Superposition and Thevenin).Generation of alternating voltages, fundamentals of ac circuits, behaviour of pure R, L, C in ac circuits, concept of phasor and its representation, series RL, RC and RLC circuits

Click here for objective questions (Electrical Machines)

Click here for MCQ Test-02

Click here for MCQ Test-03

Network Theory Test-03

2020-09-04T02:45:00.008-04:00

Network theory_Exercise-03(Analysis of DC & AC Circuits)

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Network Theory Test-02

2020-08-30T08:52:00.006-04:00

Network theory _Exercise-02 (DC Circuit :Network Theorem)

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Network Theory Test-01

2020-08-20T12:44:00.007-04:00

Network theory _Exercise-01 (DC Circuit)

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Network Theory Basics

2020-08-01T12:32:00.070-04:00

Network Theory

Network theory is the study of solving complex circuit into simple circuit. In this introductory chapter, let us first discuss the basic terminology of circuits and types of network elements.

Network Theory

Basic term :In network theory, we often encounter the following terms −

Circuit

Electrical network

current

Voltage

power

Therefore, before proceeding, some basic knowledge about these terms must be collected. Let's start with the circuit.

Circuit

The circuit contains a closed path for providing electron flow from a voltage source or a current source. The components present in the circuit can be in series, in parallel, or any combination of series and parallel.

Electrical network

Combination of circuit is called as electrical network.

Download Syllabus, Notes and Book of Network Theory ppt:

Download Syllabus of Network Theory .

Unit-I Analysis of DC and AC Circuits

Unit-II Transient Analysis

Unit-III Two Port Network

Unit-IV Filter and Attenuator

Unit-V Graph Theory

Previous Year Question Paper of TA-1 PDF

Download reference book of Network Theory pdf:

A)Schaums of Electric Circuits7th Edition-1(Ref:engbookspdf.com)

B)Schaum's Outline of Theory and Problems of Electric Circuits ( Ref:PDFDrive.com )

Concept of Super mesh and super node.

Click here for-Network theory _Exercise-01

Click here for-Network theory _Exercise-02

Click here for Solution of -Network theory _Exercise-02

Click here for-Network theory _Exercise-03

Click here for-Solution of -Network theory _Exercise-03

What is an Electrical Drives

2020-06-19T12:28:00.024-04:00

Electrical Drives :Definition, Block diagram, Classification , advantages and disadvantages.

Whenever the terms "motor" or "generator" are used, we tend to think that the speed of rotation of these machines is completely controlled by the frequency of the applied voltage and source current. However, the rotation speed of the motor can also be accurately controlled by implementing the concept of driving.

Test your Basics:Electrical Drives

The main advantage of this concept is that motion control can be easily optimized with the aid of a drive. Simply put, the system that controls the movement of a motor is called an electric drive.

A typical drive system consists of an electric motor and a complex control system that controls the rotation of the motor shaft. Today, this control can be easily done with the help of software. As a result, control becomes more and more precise, and this drive concept also provides ease of use.

Evolution of Drive :

• Came into picture with the invention of wheel in the proto historic period of 3500 BC.

• Till 18^th – 19^th century : Not much conscious effort in the control of motion

• Conscious effort to control motion : advent of steam governors

• Advent of electric motors in 19^th century led to the development of electric drive

• Conscious automatic control of drive became more wide spread.

This drive system is widely used in many industrial and home applications such as factories, transportation systems, textile mills, fans, pumps, motors, robots, and so on. The drive is used as a diesel or gasoline engine, gas or steam turbine, hydraulic prime mover motor and electric motor.

Now entering the history of electric drives, it was first designed by B.S. Iakobi in Russia in 1838, when he tested the DC motor provided by the battery and propelled the boat. Even industrial adaptation occurred many years after about 1870. Today, the application of electric drives can be seen almost everywhere.

Definition of Electric Drive:

Systems employed for imparting motion and its control. An electrical drives employing electric actuator or motor as the prime mover. A system used to control the movement of a motor is called as an electrical drives.

In other words, a driver using an electric motor is called an electric driver. Electric drives use any prime mover, such as hydraulic motors or electric motors as the main energy source. The prime mover provides mechanical energy to the drive for motion control.

Applications of electrical drives:

It is widely used in industrial and domestic applications such as

• Transportation systems

• Paper mills

• Cement Mills

• Textile mills

• Sugar Mills

• Steel Mills

• Electric Traction

• Petrochemical Industries

• Electrical Vehicles

Block diagram of the electric drive:

The figure below shows the block diagram of the electric drive. The load in the figure represents various types of equipment, including fans, pumps, washing machines and other motors. Determine the electrical load requirements based on speed and torque. Choose a motor suitable for the load capacity as the load driver.

Block Diagram
Various components of electrical drives:

The main components of the electric drive are the power modulator, motor, control unit and sensing unit. Their components will be described in detail below.

Source: For electrical drives sources are AC and DC. AC sources are single phase or three phase AC supplies

Power modulator: Power modulator performs the following functions

• Modulates power flow from the source to the motor.

• During transient operations, such as starting, braking and speed reversal, it restricts source and motor current within permissible values. Excessive current drawn from source may overload it.

• It converts electrical energy of the source in the form suitable to the motor. For example, if the source is direct current and an induction motor is used, the power modulator converts the direct current into alternating current

• It also selects the operating mode of the motor, i;e motoring or braking.

The power modulator can adjust the output power of the power supply. It controls the power from the power source to the motor so that the motor transfers the speed-torque characteristics required by the load.

During transient operations such as starting, braking and speed, excessive current drawn from the power supply can be reversed. Excessive current drawn from the power supply may overload it or cause a voltage drop. Therefore, the power modulator limits the source current and the motor current.

Control unit:

The control unit controls the power modulator, which operates at a lower voltage and power level. The control unit also operates the power modulator as required. It also generates commands to protect the power modulator and motor. Input the command signal, from the input to the control unit, adjust the working point of the driver.

Sensor:

It senses certain drive parameters, such as motor current and speed. It is mainly used for protection or closed-loop operation. From Motor it senses Speed ,Torque, Position, Current and Voltage from lines or from electric motor terminals. From Load it senses Torque and Temperature.

Advantages of electric drives:

The following are the advantages of electric drives.

· Electric drives have very large torque, speed and power ranges.

· Their work is not affected by environmental conditions.

· The electric drive has no pollution.

· The electric drive runs on all quadrants of the speed torque plane.

· The drive can be started easily without refueling.

· The efficiency of the drive is high because of low losses.

Disadvantages of electric drive:

· The power failure completely disabled the entire system.

· The application of the driver is restricted because it cannot be used in places where there is no power supply.

· Will cause noise pollution.

· The installation cost of the system is high.

· Its dynamic response is poor.

· The output power obtained from the driver is low.

· During conductor failure or short circuit, the system may be damaged, so some problems will occur.

Selection Criteria of Electrical Drives:

The choice of electric drive depends on many factors. Some important factors are.

1. Requirements for steady-state operating conditions: Properties of speed torque characteristics, speed regulation, speed range, efficiency, duty cycle, working quadrant, speed fluctuation (if any), rating, etc.

2. Transient operation requirements: Values for acceleration and deceleration, starting, braking and reversible performance.

3. Requirements related to source: Power supply type and its capacity, voltage size, voltage fluctuation, power factor, harmonics and their impact on other loads, the ability to accept regenerative power

4. Capital and operating costs, maintenance requires life.

5. Space and weight restrictions (if any).

6. Environment and location.

7. Reliability.

Types of Electrical Drives:

A variable speed drive for controlling a DC motor is called a DC drive, and a variable speed drive for controlling an AC motor is called an AC drive.

AC drives are used to drive AC motors, especially three-phase induction motors, because in most industries they have an advantage over other motors. In industrial terms, AC drives are also called variable frequency drives (VFD), variable speed drives (VSD).Based on the application and demands, drives are classified into various categories shown in below figure:

Types of electrical drives.

Test your Basics:Electrical Drives

What are the Characteristics of DC motors

2020-06-01T13:11:00.032-04:00

Characteristics of DC motors-

Characteristics of DC Motor means the relation(or graph) between different parameter like Armature Torque, Armature Current & Speed of the motor.

There are three characteristic of DC motors which are:

Torque speed characteristics
Torque current characteristics and
Current speed characteristics.

DC Motor

These are explained step by step for each type of the motor (DC Motor). These graph of DC motor are determined by keeping two things in mind first back emf equation and second torque equations. For a DC motor, magnitude of the back emf of DC motor is same as emf equation of a dc generator.

The back emf equation of DC motor are given as: Eb=(PɸNZ)/(60A)-----(i)

and armature torque equation of DC Motor is given as: Ta= 0.159(PZ/A)ɸIa-----(ii)

where P= number of poles,

Z= Total number of conductor and

A= Number of parallel path,

Hence once a motor get manufactured then P, Z and A remains constant and Therefore above equations (i) and (ii) can be written as Ta ∝ ɸ.Ia and N ∝ Eb/ɸ........(iii)

Characteristics of DC series motors- In a DC series motor the series field winding is always connected with the armature winding and DC supply is applied across it. The applied voltage or terminal voltage (supply voltage) in DC series motor is given by : Vt=Eb+IaRa+IseRse+Brush drop

Vt=Eb+Ia(Ra+Rse)+Brush drop, Eb= Vt-Ia(Ra+Rse)-Brush drop...................(iv)

The load current is given by IL=Ise=Ia and the back emf is given by equation (i).

(a)Armature Current Vs Speed Characteristic (Ia Vs N): In DC series motor the flux, which is produced by magnetic field is proportional to load current . As per the above equation(i) the speed of the motor is proportional to back emf , but back emf of DC Series motor can be given in equation (iv), Eb= Vt-Ia(Ra+Rse)-Brush drop.

In a DC series motor the voltage drop across brush terminals is very small. The resistance of the motor is also negligible, hence a change in the back emf will remains constant if we maintain terminal voltage constant. It means rotational motion i,e; speed of DC series motor is inversely proportional to load current as stated in above equation(iii) (N ∝ Eb/ɸ).

As ɸ ∝ Ise=Ia= IL, Hence N ∝ 1/ɸ ∝ 1/Ia

There will be dangerously very high speed at no load (no armature current) condition of the motor and current in the field winding is low hence flux is low. Hence DC series motor should never operates without mechanical load. The Armature Current and Speed Characteristic (Ia Vs N) is shown in figure(a).

(b)Armature Current Vs Torque Characteristic(Ia Vs Ta):From above equation(ii), we know that torque is directly proportional to the product of armature current and magnetic flux, Ta ∝ ɸ.Ia. In DC series motor the flux is directly proportional to current carried by field winding (hence load current), ɸ ∝ Ise=If (Field current).

If we increase the field current, flux will also increase up to a certain point, known as a magnetic saturation point of field core. The magnetic saturation is a capacity of a field core to hold maximum magnetic flux. Once core get saturated, after that if you increase field current then flux will remains constant. It means there will be no change in flux after saturation point.

Therefore, before magnetic saturation of the field core, ɸ is directly proportional to armature current, Hence torque is proportional to square of armature current,Ta ∝ Ia*Ia= (Ta ∝ Ia2). Hence before saturation point characteristic is a parabola.

After magnetic saturation of the field core, magnetic flux is independent of armature current, Ia. Hence, the torque directly proportional to Ia , Ta ∝ Ia. Therefore, armature current- torque curve becomes a straight line after magnetic saturation of the field core.

Before magnetic saturation torque increases as the square of armature current, therefore DC Series motors are used where high starting torque is required. The Armature Current and Torque (Ia Vs Ta) characteristics is shown in figure(b).

(c)Torque Vs Speed Characteristic (Ta Vs N):Torque is proportional to square of the armature current, Ta α Ia2. The speed of DC series motor is N ∝ Eb/ɸ. Hence if the torque on the DC shunt motor increased the armature current also increases, thus flux increases and speed will be dropped as N ∝1/square root Ta .

As the load goes on increasing speed of DC series motor will drop rapidly. This characteristic is also known as mechanical characteristic of DC motor. The Torque and Speed Characteristic (Ta Vs N) is shown in figure(c).

Characteristics of DC Series motor.

Characteristics of DC shunt motor

In DC Shunt motor the shunt field winding and the armature is connected in parallel and DC supply voltage is applied across it. The applied voltage or terminal voltage,Vt in DC shunt motor is given by : Vt=Eb+IaRa+Brush drop

Eb= Vt-IaRa-Brush drop

Vt=I_shR_sh I_sh= Vt/ R_sh................. ...............(v)

The line current is given by I_L=I_sh+I_a and the back emf, Eb is given by equation (i).

(a)Armature Current Vs Speed Characteristic (Ia Vs N): As we know that flux ɸ, is directly proportional to field current. In DC shunt motor field current ,If=Ish= Vt/ R_sh,hence in DC shunt motor if supply voltage and shunt field resistance is constant then the flux is constant as current Ish, carried by field winding is constant.

Therefore DC shunt motor is also known as constant flux motor. Hence equation (iii) speed is proportional to back emf, N ∝ E_b/ɸ ∝ ( Vt-IaRa-Brush drop)/ɸ. The shunt field resistance and voltage drop across brush is very less, hence change in back emf Eb will remains constant if we maintain terminal voltage Vt constant. This indicate that the speed of DC shunt motor is almost constant with respect to armature or load current.

Hence DC shunt motor can be assumed as a constant speed motor. The characteristic is slightly dropping due to presence of voltage drop in back emf by IaRa drop which is very small. The Armature Current and Speed Characteristic (Ia Vs N) is shown in figure(d).

(b)Armature Current Vs Torque Characteristic(I_aVs T_a): In DC shunt motor the flux is constant as current carried by field winding is constant. From equation (iii), we know that the torque is proportional to product of field flux and armature current, T_a ∝ ɸ.I_a .But as we have stated above that the flux of DC shunt motor is assumed to be constant.

Hence the torque is proportional to armature current, T_a ∝ I_a , and therefore current and speed characteristic is linear passing through origin. The Armature Current and Torque (Ia Vs Ta) characteristics is shown in figure(e).

(c)Torque Vs Speed Characteristic (Ta Vs N): In DC shunt motor the flux is assumed to be constant hence to armature current, T_a ∝ I_a .

The speed of DC shunt motor is N ∝ E_b/ɸ∝( Vt-IaRa-Brush drop)/ɸ . Hence as the torque on the DC shunt motor increases the armature current increases and speed will be dropped by some value. But the characteristic is slightly dropping.

This characteristic is also known as mechanical characteristic of DC motor. The Torque and Speed Characteristic (Ta Vs N) is shown in figure(f).

Characteristics of DC Shunt Motor

Characteristics of DC compound motor-DC compound motors have two field winding, series as well as shunt winding. Series field winding is always connected in series with armature winding. Based on the total flux in motor there are two types of compound motor.

1.Cumulative compound motor
2.Differential compound motor

In a compound motor if the nature of both flux is additive, if series and shunt windings are connected in such way that the direction of series flux is same as the shunt flux then the motor is said to be cumulative compound motor.

And a compound motor if the nature of both flux is subtractive, if series and shunt windings are connected in such way that the direction of series flux is opposite to the shunt flux then the motor is said to differential compound motor.

Characteristics of these compound motors are shown below:

characteristics of compound motor

Steps to find UGC Scopus and web of Science Journal list

2020-05-20T09:19:00.010-04:00

UGC Journal list:-

Union Grants Commission's(UGC) Approved List of Journals:-

As per the UGC guidelines, the UGC Approved List of Journals has been replaced by UGC-CARElist w.e.f. 14.06.2019

UGC-CARE: Union Grants Commission's(UGC) for Consortium for Academic Research and Ethics (CARE)

The UGC-CARE List is dynamic and number of journal is changing time to time. If any good quality journal is missing, it may be submitted and updated by the prescribed process and if any undeserved journal is found anywhere in the List, it may kindly be reported through feedback option and removed from the list by the prescribed process.

Union Grants Commission's(UGC) for Consortium for Academic Research and Ethics (CARE) List is divided into category i) Sciences ii) Social Sciences iii) Arts and Humanities and iv) Multidisciplinary

1.UGC-CARE journal list: By clicking below you have to register first with your email id and set a password.

https://ugccare.unipune.ac.in/Apps1/User/WebA/SearchList

2.List of Journals indexed in Web of Science

https://mjl.clarivate.com/search-results

3.List of Journals Scopus indexed (Elsevier)

https://journalfinder.elsevier.com/

Steps to find UGC Scopus and web of Science Journal list

Can DC Series motor operates at no load condition

2020-05-18T12:40:00.018-04:00

Why DC Series motor can not operates at no load condition

What are the types of DC Motors?

The construction of dc motor is same as dc generator.DC motor are two types Self excited motor and separately excited motor.Based on field winding connection with armature winding self excited motor are divided into three category namely dc series motor, dc shunt motor and dc compound motor.

Take a test:DC Machines

What is DC Series Motor?

As the name indicates, in DC series motor field winding is connected in series with the armature winding. Hence Line current(I_L), Field current (I_se=I_f), and armature current (Ia) all are equal

I_L=I_f=Ia---------------(i)

DC series motor

Armature current of any DC motor depends upon load. Hence if load increases armature current (Ia) also increases and vice versa. At no load condition, load on the motor is zero hence armature current(Ia) is also zero. From equation (i) (I_f=Ia) hence field current(I_f) will also=0 at no load condition.

Now as we know that flux of any DC motor is directly proportional to field current (I_f).We can easily understand this with the help of back emf equation of DC motor:

Basic equations

Hence based on above discussion it is advised that DC Series motor should not operate at no load condition.We can also understand above by knowing characteristics of DC series motor.

How to solve numerical on DC Series Motor? Step by step process:

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Take a test:DC Machines

Engineering Talk:Electrical Engineering Forum

MCQ Test V on Electric Drive and Speed Control

Objective Test on Electric Drive and Speed Control

MCQ Test on Power Semiconductor Device

Objective Test on Power Semiconductor Device

MCQ Test on Three phase Synchronous motor

Objective Test on Three phase Synchronous motor

Three Phase Induction motor working Principle and its Types

MCQ Test-01 on DC Machines

MCQ Test on Transducer

MCQ Test on Digital Electronics

MCQ Test on Diode and Diode circuits

Objective practice test on Diode and Diode circuits

Questions on Basics of Electronics and Transducer

MCQ Test on transformer and DC Machines

Objective Test transformer and DC Machines

Questions on Basic Electrical DC and AC Circuits

Assignment Questions: Basics of Electrical and Electronics Engineering

Network Theory Quiz

MCQ Test 01 on DC and AC circuits

Basic Electrical Test

Basics of electrical and electronics engineering

Analysis of DC circuit and AC circuit:

Network Theory Test-03

Network Theory Test-02

Network Theory Test-01

Network Theory Basics

Network Theory

Download Syllabus, Notes and Book of Network Theory ppt:

Download reference book of Network Theory pdf:

What is an Electrical Drives

Electrical Drives :Definition, Block diagram, Classification , advantages and disadvantages.

Evolution of Drive :

Definition of Electric Drive:

Applications of electrical drives:

Block diagram of the electric drive:

Block DiagramVarious components of electrical drives:

Power modulator: Power modulator performs the following functions

Control unit:

Sensor:

Advantages of electric drives:

Disadvantages of electric drive:

Selection Criteria of Electrical Drives:

Types of Electrical Drives:

What are the Characteristics of DC motors

Characteristics of DC Series motor.

Characteristics of DC shunt motor

(c)Torque Vs Speed Characteristic (Ta Vs N): In DC shunt motor the flux is assumed to be constant hence to armature current, Ta ∝ Ia .

Steps to find UGC Scopus and web of Science Journal list

UGC Journal list:-

Union Grants Commission's(UGC) Approved List of Journals:-

Can DC Series motor operates at no load condition

Why DC Series motor can not operates at no load condition

What are the types of DC Motors?

What is DC Series Motor?

Block Diagram
Various components of electrical drives:

(c)Torque Vs Speed Characteristic (Ta Vs N): In DC shunt motor the flux is assumed to be constant hence to armature current, T_a ∝ I_a .