The book assumes basic understanding of the fundamentals of Electrical Engineering and related basic electronics. The exam serves as a reference point for the normalization of university engineering education in the country.
APPLYING FOR THE EXAMINATION
While admission to a top institute for Master's program continues to be the most important reason to work hard to secure a good score in the GATE exam; another reason to appear and qualify the GATE exam with good scores is that many Public Sector Undertakings (PSEs) are and probably in the future almost all will be recruiting through the GATE exam. In 2015, 15 PSUs signed agreements with IIT Kanpur to receive GATE 2015 results in various documents.
STRUCTURE OF THE EXAMINATION
UNDERSTANDING GATE RELATED INFORMATION
This assumption is justified as the number of candidates appearing in multi-session papers in GATE 2015 is large and the process of allotting sessions to candidates is random. In addition, it is also guaranteed that for the same document for multiple sessions, the number of candidates allocated in each session is of the same order of magnitude.
ATTRIBUTES FOR SUCCESS IN THE EXAMINATION
For the aforementioned works; The GATE score will be calculated based on the normalized marks and not the actual marks obtained in the exam. University exams or work deadlines will cut into the time you seem to have.
TAKING THE EXAMINATION
Attempt as many previous years GATE questions based on the topic and follow the above approach for self evaluation. Since the syllabus to be covered is very large, time management plays a key role in effective preparation.
SYLLABUS FOR ELECTRICAL ENGINEERING (EE)
Single phase transformer: equivalent circuit, phasor diagram, open circuit and short circuit tests, regulation and efficiency; Three-phase transformers: connections, parallel operation; Auto transformer, Electromechanical energy conversion principles, DC machines: separately excited, series and shunt, motor and excitation mode of operation and their characteristics, starting and speed control of DC motors; Three-phase induction motors: principle of operation, types, performance, torque-speed characteristics, no-load and locked rotor tests, equivalent circuit, starting and speed control; Principle of operation of single phase induction motors; Synchronous machines: cylindrical and salient pole machines, performance, regulation and parallel operation of generators, starting of synchronous motor, characteristics;. Buck, Boost and Buck-Boost converters; Single and three-phase configuration of uncontrolled rectifiers, Line-communicated thyristor-based converters, Bidirectional AC to DC voltage source converters, Issues of line current harmonics, Power factor, Distortion factor of AC to DC converters, Single-phase and three-phase converters, Sinusoidal pulse width modulation.
CONTENTS
MARKS DISTRIBUTION FOR GATE QUESTIONS
2015 Electric and magnetic fields, Network solution and methodology, Sinusoidal steady state analysis, Laplace transform, Two port network. 2012 KVL, KCL, Network theorem, Transient and steady state analysis, Filters, Maximum power transfer theorem, Thevenin/Norton theorems, Two port network, AC.
ELECTRIC CIRCUITS
CIRCUIT CONCEPTS AND LAWS
If the V-I characteristics of an element are as shown in Figure 1.14, then the element is nonlinear, passive, and bilateral. If the V-I characteristics of an element are as shown in Figure 1.17, then the element is linear, active, and bidirectional.
CIRCUIT ANALYSIS TECHNIQUES
The voltage across the 5 Ω resistor is V. 2) Problem 1.10: Determine the power delivered by the 10 V source in the following circuit. Since there is a break in the KVL in the network, the circuit connection is physically not possible.
TOPOLOGY
The number of branches that occur at a node of a graph indicates the degree of the node. A matrix representing the relationship between number of branches and number of nodes in a directed graph is known as incidence matrix.
NETWORK THEOREMS
This network contains only dependent source, so its Q. Problem 1.40: Find the Thevenin equivalent circuit for the following circuit. V is applied between terminals a and b. 10.6) Problem 1.42: Find the Thevenin equivalent source voltage and resistance for the following circuit.
LAPLACE TRANSFORM
The initial value theorem helps to find the initial value of f (t) from an s-domain expression. The final value theorem helps to find the final value of f (t) from an s-domain expression.
TRANSIENT RESPONSE TO DC AND AC NETWORKS
- AC TRANSIENTS
In steady state, energy stored in the network is maximum and constant, that is, the energy stored in the inductor and capacitor is maximum and constant. In a source-free RL circuit, the source is suddenly cut off and we choose the inductor current as the response, since the inductor current cannot change instantaneously. A source-free RC circuit is a circuit in which the DC source is suddenly cut off and the energy already stored in the capacitor is dissipated through the resistor (Fig. 1.65).
If there is no external source of excitation in the circuit, the resulting response is called the natural response of the circuit.
Hsin(ωt)
Note: From the above condition, if the total phase of the excitation at the time of switching is equal to tan−1 wL. For the circuit shown in the figure below, the source frequency is 50 Hz. 0 leading to a transient free response.
F 10cos(2t+ p /4) i(t)
The transient-free response mode is not possible for the networks with both types of elements, i.e. inductor and capacitor. When the LC elements are present in the circuit, complex roots will always result in the transient response.
SINUSOIDAL STEADY STATE ANALYSES USING PHASORS
The phasor diagrams along with the characteristic equations for different circuits are discussed as follows. L∠ °90 In any RL circuit due to the inductances, the current lags the voltage, therefore the phasor diagram as shown in Fig. 90. Three phasor diagrams are possible depending on the relationship between capacitor and inductor current, that is IC > I. The expressions for characteristic parameters are listed in Table 1.8.
In the circuit shown in the figure given below, if I I. 1.7 Sinusoidal Steady State Analyzes Using PHASORS 69 .
MAGNETICALLY COUPLED CIRCUITS
RESONANCE
The quality factor of a resonant circuit is the ratio of its resonant frequency to its bandwidth. At resonance, the voltages across the inductor and capacitor increase by Q times (more than 1), so these circuits are called resonance voltage boosting circuits. Because the circuit takes maximum current at resonance compared to any other operating frequency.
At resonance, the circuit rejects a fraction of the current compared to any other operating frequency.
FILTERS
Active Filters: Filters consisting of active devices such as operational amplifiers that tend to amplify signals are called active filters. Inductors are not preferred in the design of active filters because their size is bulky and their cost is high. Passive Filters: These filters contain only passive components in the circuit i.e. series and parallel connections of inductor and capacitors.
Low-pass filter (LPF): A filter that passes low frequencies and stops high frequencies is called a low-pass filter (Fig. 1.100).
THREE-PHASE CIRCUITS
The YNs are exactly equal in magnitude and each has a progressive phase shift of 120°, as shown in Fig. Now, if the three-phase load is such that the magnitudes and angles of each of the three phases are equal, then the three-phase load is balanced.
AC POWER ANALYSIS
The RMS value of any periodic current is equal to the value of the DC current flowing through an R-ohm resistor and delivering the same average power to the resistor as the periodic current. The rms values of the sine or cosine function of each phase and frequency are the maximum value/2. Find both the average power and an expression for the instantaneous power resulting when the corresponding phasor voltage V = 4∠ °0 V is applied across an impedance Z = 2∠ °60 W.
TWO-PORT NETWORK
Parallel connection of two-port network The short-circuit admittance parameters are used for the characterization of parallel two-port network (Fig. 1.112). Series connection of two-port networks When two networks A and B are connected in series with Z parameters [Z. Cascade connection of two-port networks The transmission parameters are useful for describing two-port networks which are connected in cascade (Fig. 1.114).
If these two networks are daisy-chained, then so is the admission parameter of the total two-port network.
IMPORTANT FORMULAS
Series Impedance and Voltage Division R Z V. Mesh Analysis: Steps to Follow. ii) Assign the mesh current. iii). Node analysis: steps to follow (i) Identify the nodes. ii) Assign the node voltage and ground node. iii) Write node equations using KCL's law + Ohm's law. General formula for calculating current through inductor.). g) Source-driven RLC circuit in parallel V t L. h) Source-driven RLC circuit in series i t C.
Phasor relationship for circuit elements. a) When current and voltage are in the same phase V = RI.
SOLVED EXAMPLES
In the circuit shown in the figure below, the switch is in position 1 for a long time and it is moved to position 2 at t = 0. In the circuit given in the following figure, the switch is for ' closed for a long time and is opened at t = 0. Solution: When the switch is at position 1 for a long time, then current through capacitor is zero and voltage across capacitor at E is as shown in the following figure.
In the given circuit, if the current through the resistor R is zero, what is the value of I.
PRACTICE EXERCISES
In the circuit given below, the current I. The circuit given below is initially in steady state. Determine the current (I) and average power. Pavg) in the circuit shown in the figure below. In the circuit shown in the figure below, steady state is achieved with S open.
For the circuit shown in the figure below, the switch is closed for a long time and it opens at t = 0.
ANSWERS TO PRACTICE EXERCISES
Since the two cosines have different frequencies, the two mean power values can be. If two lamps are connected in series, the circuit is A. Applying the current loop method and KVL equation for loop current I. Applying Cramer's rule, we get. In the following equivalent circuit 2Ω. b) Parallel combination of each 5 Ω on the left side, then convert to voltage source as shown in the following figure.
The output voltage across capacitance is V I X. c) Applying ∆ to star conversion on the upper delta, we get.
SOLVED GATE PREVIOUS YEARS’ QUESTIONS
Therefore, the potential difference between P and Q is V. Two AC sources feed a common variable resistive. load as shown in the figure below. Under the maximum power transfer condition, the power absorbed by the load resistor R. To obtain Thevenin impedance, short-circuit the source. The value of Z in the figure below. is best suited to cause parallel resonance at 500 Hz.
For the two-port network shown in the figure below, the value of h. as for open circuit I.
From the graph,
2 Ω provides a passive non-linear resistance characterized by the relation V. The power delivered in the non-linear resistance is. Then the Thevenin voltage is represented as, V. 1 is the input voltage applied at port A. AB= DC = 3A, since the output current from A to B is equal to the input current from D to C;. the circuit is one-port network. Provided that both voltage sources are in phase. the value of R for which maximum power is transferred from circuit A to circuit B is.
In the circuit shown, the three voltmeter readings are V. The power factor of the load is.
ELECTROMAGNETIC FIELDS
COULOMB’S LAW
ELECTRIC FIELD INTENSITY
