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electrical engineering

Questions and Answers of Electrical Engineering

Repeat Problem 10.2 for TV channels, each requiring a bandwidth of 6 MHz.
A geostationary satellite is at a distance of 40,000 km from a ground receiving station. The satellite transmitting antenna is a circular aperture with a 1-m diameter and the ground station uses a
A collision avoidance automotive radar is designed to detect the presence of vehicles up to a range of 0.5 km. What is the maximum usable PRF?
A 10-GHz weather radar uses a 15-cm-diameter lossless antenna. At a distance of 1 km, what are the dimensions of the volume resolvable by the radar if the pulse length is 1 μs?
A radar system is characterized by the following parameters: Pt = 1 kW, 0 1 μs, G = 30 dB, 3 cm, and Tsys = 1,500 K. The radar
A 3-cm-wavelength radar is located at the origin of an x€“y coordinate system. A car located at x = 100 m and y = 200 m is heading east (x-direction) at a speed of 120 km/hr. What is the
A magnetic circuit with a single air gap is shown in Figure. The core dimensions are: Cross-sectional area Ac = 1.8 ? 10?3 m2 Mean core length lc = 0.6 m Gap length g = 2.3 x 10?3 m N = 83
Repeat Problem 1.1 for a finite core permeability of μ = 2500μ0.
Consider the magnetic circuit of Figure with the dimensions of Problem 1.1. Assuming infinite core permeability, calculate(a) The number of turns required to achieve an inductance of 12 mH and(b) The
Repeat Problem 1.3 for a core permeability of μ = 1300 μ0.
The magnetic circuit of Problem 1.1 has a nonlinear core material whose permeability as a function of Bm is given by where Bm is the material flux density. a. Using MATLAB, plot a dc magnetization
The magnetic circuit of figure consists of a core and a moveable plunger of width lp, each of permeability ?. The core has cross-sectional area A and means length Ac. The overlap area of the two air
The magnetic circuit of figure and Problem 1.6 has the following dimensions: Ac = 8.2cm2 lc = 23cm lp = 2.8 cm g = 0.8 mm X0 = 2.5 cm N = 430 turns a. Assuming a constant permeability of ? = 2800?0,
An inductor of the form of figure has dimensions: Cross-sectional area Ac = 3.6 cm2 Mean core length lc = 15 cm N = 75 turns Assuming a core permeability of μ = 2100μ0 and neglecting the effects of
The magnetic circuit of Figure consists of rings of magnetic material in a stack of height h. The rings have inner radius Ri and outer radius R0. Assume that the iron is of infinite permeability (? =
Repeat Problem 1.9 for a core permeability of μ = 75μ0.
Using MATLAB, plot the inductance of the inductor of Problem 1.9 as a function of relative core permeability as the core permeability varies for μr = 100 to μr = 10000. What is the minimum relative
The inductor of figure has a core of uniform circular cross-section of area Ac, mean length lc and relative permeability ?r and an N-turn winding. Write an expression for the inductance L.
The inductor of figure has the following dimensions: Ac = 1.0 cm2 lc = 15 cm g = 0.8 mm N = 480 turns Neglecting leakage and fringing and assuming ?r = 1000, calculate the inductance.
The inductor of Problem 1.13 is to be operated from a 60-Hz voltage source.(a) Assuming negligible coil resistance, calculate the rms inductor voltage corresponding to a peak core flux density of 1.5
Consider the magnetic circuit of Figure. This structure, known as a pot-core, is typically made in two halves. The N-turn coil is wound on a cylindrical bobbin and can be easily inserted over the
A square voltage wave having a fundamental frequency of 60 Hz and equal positive and negative half cycles of amplitude E is applied to a 1000-turn winding surrounding a closed iron core of 1.25 x
A square voltage wave having a fundamental frequency of 60 Hz and equal positive and negative half cycles of amplitude E is applied to a 1000-turn winding surrounding a closed iron core of 1.25 x
Consider the inductor of Problem 1.17. Write a simple design program in the form of a MATLAB script to calculate the number of turns and air-gap length as a function of the desired inductance. The
A proposed energy storage mechanism consists of an N-turn coil wound around a large nonmagnetic (? = ?0) toroidal form as shown in Figure. As can be seen from the figure, the toroidal form has a
Figure shows an inductor wound on a laminated iron core of rectangular cross section. Assume that the permeability of the iron is infinite. Neglect magnetic leakage and fringing in the two air gaps
The inductor of figure has the following dimensions: a = h = w = 1.5cm b = 2cm g = 0.2cm The winding factor (i.e., the fraction of the total winding area occupied by conductor) is fw = 0.55. The
The magnetic circuit of figure has two windings and two air gaps. The core can be assumed to be of infinite permeability. The core dimensions are indicated in the figure. a. Assuming coil 1 to be
The symmetric magnetic circuit of Figure has three windings. Windings A and B each have N turns and are wound on the two bottom legs of the core. The core dimensions are indicated in the figure. a.
The reciprocating generator of Figure has a movable plunger (position x) which is supported so that it can slide in and out of the magnetic yoke while maintaining a constant air gap of length g on
Figure shows a configuration that can be used to measure the magnetic characteristics of electrical steel. The material to be tested is cut or punched into circular laminations which are then stacked
From the dc magnetization curve of figure it is possible to calculate the relative permeability μr = Bc/(μ0Hc) for M-5 electrical steel as a function of the flux level Bc. Assuming the core of
In order to test the properties of a sample of electrical steel, a set of laminations of the form of figure have been stamped out of a sheet of the electrical steel of thickness 3.0 mm. The radii of
The coils of the magnetic circuit shown in figure are connected in series so that the mmf's of paths A and B both tend to set up flux in the center leg C in the same direction. The coils are wound
The following table includes data for the top half of a symmetric 60-Hz hysteresis loop for a specimen of magnetic steel: Using MATLAB, (a) Plot this data, (b) Calculate the area of the hysteresis
Assume the magnetic circuit of Problem 1.1 and figure to be made up of M-5 electrical steel with the properties described in figures. Assume the core to be operating with a 60-Hz sinusoidal flux
Repeat Example 1.8 under the assumption that all the core dimensions are doubled.
Using the magnetization characteristics for samarium cobalt given in figure, find the point of maximum energy product and the corresponding flux density and magnetic field intensity. Using these
Using the magnetization characteristics for neodymium-iron-boron given in figure find the point of maximum-energy product and the corresponding flux density and magnetic field intensity, using these
Figure shows the magnetic circuit for a permanent-magnet loudspeaker. The voice coil (not shown) is in the form of a circular cylindrical coil which fits in the air gap. A samarium-cobalt magnet is
It is desired to achieve a time-varying magnetic flux density in the air gap of the magnetic circuit of figure of the form Bg = B0 + B1 sin wt where B0 = 0.5 T and Bl = 0.25 T. The dc field B0 is to
A transformer is made up of a 1200-turn primary coil and an open-circuited 75-turn secondary coil wound around a closed core of cross-sectional area 42 cm2. The core material can be considered to
A transformer is to be used to transform the impedance of a 8-Ω resistor to an impedance of 75 ft. Calculate the required turns ratio, assuming the transformer to be ideal.
A 100-Ω resistor is connected to the secondary of an idea transformer with a turns ratio of 1:4 (primary to secondary). A 10-V rms, 1-kHz voltage source is connected to the primary. Calculate the
A source which can be represented by a voltage source of 8 V rms in series with an internal resistance of 2k Ω is connected to a 50-Ω load resistance through an ideal transformer. Calculate the
Repeat Problem 2.5 with the source resistance replaced by a 2-kΩ reactance.
The manufacturer calculates that the transformer of Problem 2.7 has a secondary leakage inductance of 0.225 mH.a. Calculate the magnetizing inductance as referred to the secondary side.b. A voltage
A 120-V: 2400-V, 60-Hz, 50-kVA transformer has a magnetizing reactance (as measured from the 120-V terminals) of 34.6 Ω. The 120-V winding has a leakage reactance of 27.4m Ω and the 2400-V
A 460-V: 2400-V transformer has a series leakage reactance of 37.2Ω as referred to the high-voltage side. A load connected to the low-voltage side is observed to be absorbing 25 kW, unity power
The resistances and leakage reactance’s of a 30-kVA, 60-Hz, 2400-V: 240-V distribution transformer are R1 = 0.68 Ω R2 = 0.0068 Ω, X11 = 7.8 Ω X12 = 0.0780 Ω where subscript 1 denotes the
Repeat Problem 2.11 for a 75-kVA, 60-Hz, 4600-V: 240-V distribution transformer whose resistances and leakage reactance’s are R1 = 0.846 Ω R2 = 0.00261 Ω X11 = 26.8 Ω X12 = 0.0745 Ω where
A single-phase load is supplied through a 35-kV feeder whose impedance is 95 + j360 Ω and a 35-kV: 2400-V transformer whose equivalent impedance is 0.23 + j 1.27 Ω referred to its low-voltage
Repeat Example 2.6 with the transformer operating at full load and unity power factor.
The nameplate on a 50-MVA, 60-Hz single-phase transformer indicates that it has a voltage rating of 8.0-kV: 78-kV. An open-circuit test is conducted from the low-voltage side, and the corresponding
A 550-kVA, 60-Hz transformer with a 13.8-kV primary winding draws 4.93 A and 3420 W at no load, rated voltage and frequency. Another transformer has a core with all its linear dimensions ~ times as
The following data were obtained for a 20-kVA, 60-Hz 2400: 240-V distribution transformer tested at 60 Hz:a. Compute the efficiency at full-load current and the rated terminal voltage at 0.8 power
The transformer of Problem 2.11 is to be connected as an autotransformer. Determine(a) The voltage ratings of the high- and low-voltage windings for this connection and(b) The kVA rating of the
A 120: 480-V, 10-kVA transformer is to be used as an autotransformer to supply a 480-V circuit from a 600-V source. When it is tested as a two-winding transformer at rated load, unity power factor,
Consider the 8-kV: 78-kV, 50-MVA transformer of Problem 2.15 connected as an autotransformer.a. Determine the voltage ratings of the high- and low-voltage windings for this connection and the kVA
The high-voltage terminals of a three-phase bank of three single-phase transformers are supplied from a three-wire, three-phase 13.8-kV (line-to-line) system. The low-voltage terminals are to be
Three 100-MVA single-phase transformers, rated at 13.8 kV: 66.4kV, are to be connected in a three-phase bank. Each transformer has a series impedance of 0.0045 + j0.19 Ω referred to its 13.8-kV
Repeat Example 2.8 for a load drawing rated current from the transformers at unity power factor.
A three-phase Y-∆ transformer is rated 225-kV: 24-kV, 400 MVA and has a series reactance of 11.7 Ω as referred to its high-voltage terminals. The transformer is supplying a load of 325 MVA, with
Assume the total load in the system of Problem 2.26 to remain constant at 325 MVA. Write a MATLAB script to plot the line-to-line voltage which must be applied to the sending end of the feeder to
A ∆-Y-connected bank of three identical 100-kVA, 2400-V: 120-V, 60-Hz transformers is supplied with power through a feeder whose impedance is 0.065 + j0.87 Ω per phase. The voltage at the sending
A 7970-V: 120-V, 60-Hz potential transformer has the following parameters as seen from the high-voltage (primary) winding: X1 = 1721 Ω X2 = 1897 Ω Xm = 782k Ω, R1 = 1378 Ω R2 = 1602 Ωa.
For the potential transformer of Problem 2.29, find the maximum reactive burden (minimum reactance) which can be applied at the secondary terminals such that the voltage magnitude error does not
Consider the potential transformer of Problem 2.29.a. Use MATLAB to plot the percentage error in voltage magnitude as a function of the magnitude of the burden impedance (i) for a resistive burden of
A 200-A: 5-A, 60-Hz current transformer has the following parameters as seen from the 200-A (primary) winding: X1 = 745μ Ω X’2 = 813μ Ω Xm = 307m Ω R1 = 136μ Ω R2 = 128μ Ωa. Assuming
Consider the current transformer of Problem 2.32.a. Use MATLAB to plot the percentage error in current magnitude as a function of the magnitude of the burden impedance (i) for a resistive burden of
A 15-kV: 175-kV, 125-MVA, 60-Hz single-phase transformer has primary and secondary impedances of 0.0095 + j0.063 per unit each. The magnetizing impedance is j 148 per unit. All quantities are in per
The nameplate on a 7.97-kV: 460-V, 75-kVA, single-phase transformer indicates that it has a series reactance of 12 percent (0.12 per unit).a. Calculate the series reactance in ohms as referred to (i)
a. Consider the Y-Y transformer connection of Problem 2.35, part (b). If the rated voltage is applied to the high-voltage terminals and the three low-voltage terminals are short-circuited, calculate
A three-phase generator step-up transformer is rated 26-kV: 345-kV, 850 MVA and has a series impedance of 0.0035 + j0.087 per unit on this base. It is connected to a 26-kV, 800-MVA generator, which
Suppose a knowledge base contains just one sentence Эx As High As (x, Everest). Which of the following arc legitimate results of applying Existential Instantiation?a. As High As (Everest,
Suppose a knowledge base contains just one sentence Эx As High As (x, Everest). Which of the following arc legitimate results of applying Existential Instantiation?a. As High As (Everest,
Calculate the magnetic stored energy in the magnetic circuit of Example 1.2.
An inductor has an inductance which is found experimentally to be of the form where L0 = 30 mH, x0 = 0.87 mm, and x is the displacement of a movable element. Its winding resistance is measured and
Repeat Problem 3.4, assuming that the inductor is connected to a voltage source which increases from 0 to 0.4 V (part [a]) and then is held constant at 0.4 V (part [b]). For both
The inductor of Problem 3.4 is driven by a sinusoidal current source of the form i (t) = I0 sin wt where I0 = 5.5 A and w = 100π (50 Hz). With the displacement held fixed at x = x0, calculate(a) The
An actuator with a rotating vane is shown in fig you may assume that the permeability of both the core and the vane are infinite (? ? ?). The total air-gap length is 2g and shape of the vane is such
An RC circuit is connected to a battery, as shown in figure. Switch S is initially closed and is opened at time t = 0. a. Find the capacitor voltage vC(t) for t > 0 b. What are the initial and
An RL circuit is connected to a battery, as shown in figure. Switch S is initially closed and is opened at time t = 0. a. Find the inductor current iL (t) for t > 0. b. What are the initial and
The L/R time constant of the field winding of an 500-MVA synchronous generator is 4.8 s. At normal operating conditions, the field winding is known to be dissipating 1.3 MW. Calculate the
The inductance of a phase winding of a three-phase salient-pole motor is measured to be of the form L (θm) = L0 + L2 cos 2θm where θm is the angular position of the rotor.a. How many poles are on
Cylindrical iron-clad solenoid actuators of the form shown in figure are used for tripping circuit breakers, for operating valves, and in other applications in which a relatively large force is
Consider the plunger actuator of figure. Assume that the plunger is initially fully opened (g = 2.25 cm) and that a battery is used to supply a current of 2.5 A to the winding. a. If the plunger is
As shown in figure, an N-turn electromagnet is to be used to lift a slab of iron of mass M. The surface roughness of the iron is such that when the iron and the electromagnet are in contact, there is
Data for the magnetization curve of the iron portion of the magnetic circuit of the plunger actuator of Problem 3.12 are given below: a. Use the MATLAB poly fit function to obtain a 3'rd-order fit of
An inductor is made up of a 525-turn coil on a core of 14-cm2 cross-sectional area and gap length 0.16 mm. The coil is connected directly to a 120-V 60-Hz voltage source. Neglect the coil resistance
Figure shows the general nature of the slot-leakage flux produced by current i in a rectangular conductor embedded in a rectangular slot in iron. Assume that the iron reluctance is negligible and
A long, thin solenoid of radius r0 and height h is shown in figure. The magnetic field inside such a solenoid is axially directed, essentially uniform and equal to H = Ni/h. The magnetic field
An electromechanical system in which electric energy storage is in electric fields can be analyzed by techniques directly analogous to those derived in this chapter for magnetic field systems.
A capacitor (Figure) is made of two conducting plates of area A separated in air by a spacing x. The terminal voltage is v, and the charge on the plates is q. The capacitance C, defined as the ratio
Figure shows in schematic form an electrostatic voltmeter, a capacitive system consisting of a fixed electrode and a moveable electrode. The moveable electrode is connected to a vane which rotates on
The two-winding magnetic circuit of figure has a winding on a fixed yoke and a second winding on a moveable element. The moveable element is constrained to motion such that the lengths of both air
Two coils, one mounted on a stator and the other on a rotor, have self- and mutual inductances of L11 = 3.5mH L22 = 1.8mH L12 = 2.1cos θ mH where θ is the angle between the axes of the coils. The
Two windings, one mounted on a stator and the other on a rotor, have self- and mutual inductances of L11 = 4.5H L22 = 2.5H L12 = 2.8cos ? H where ? is the angle between the axes of the windings. The
A loudspeaker is made of a magnetic core of infinite permeability and circular symmetry, as shown in figures a and b. The air-gap length g is much less than the radius r0 of the central core. The
Repeat Example 3.8 with the samarium-cobalt magnet replaced by a neodymium-iron-boron magnet.
The magnetic structure of figure is a schematic view of a system designed to support a block of magnetic material (? ? ?) of mass M against the force of gravity. The system includes a permanent

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