Ultimate Engineering Study Guide - Questions & Answers

Question 3 3.1. Two identical 3-phase star-connected generators supplying equal power operates in parallel. Each machine has synchronous impedance of (2 + j40) ohms per phase. They supply a total of 100 kW at 600 V and 0.8 power factor lagging. The field of the first generator is so excited that its armature current is 55 A (lagging). Determine 3.1.1 The induced voltage of the first generator [6] 3.1.2 The armature of the second generator [3] 3.1.3 The power factor and induced voltage of the second generator [4] 3.2. Two generators (G1 and G2) of similar ratings are connected in parallel. What happens when: 3.2.1. Speed of the governor of G1 is increased. [2] 3.2.2. Field current of G2 is increased [2]
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Problem 2. Impulse Response of Discrete-Time LTI System (8 points) Let (nand yind be the input and output signals of an LTI system H, respectively. Fourier transform of its impulse response is given as follows: e-1 (1-enle-3291) 1 - Te-3 + be-321 H() a) Simplify (en) and find the difference equation of the system (in other words, describe the relationship between a[n) and y[n]). Hint: You can use partial fraction expansion for simplifying the H(en). 6 b) Let hin be the impulse response of the system. Find the first five samples (n = 0,1,2, 3, 4) of h[n]. Assume y[n] = 0 for n
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22 (25 pts.) Given the difference equation 3 Using z-transform methods determine the closed form solution y(k) fork - 0.1.2.. where u(k) = discrete time unit step function and the initial conditions are y(0) 1 and y1) ** >(x + 2) - Y+ + 1) + 3(k) = (
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A four-pole, fifteen horsepower three- phase induction motor designed by Engr. JE Orig has a blocked rotor reactance of 0.5 ohm per phase and an effective ac resistance of 0.2 ohm per phase. At what speed the motor will develop maximum torque if the motor has rated input power of 18 horsepower.
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A uniform quantizer operating on samples has a data rate of 6 kbps and the sampling a rate is 1 kHz. However, the resulting signal-to-quantization noise ratio (SNR) of 30 dB is not satisfactory for the customer and at least an SNR of 40 dB is required. What would be the minimum data rate in kbps of the system that meets the requirement? What would be the minimum transmission bandwidth required if 4-ary signalling is used? Show all your steps.
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ii) A single sideband AM signal (SSB-SC) is given by s(t) = 10cos(11000 vt). The carrier signal is c(t) = 4cos(10000rrt). Determine the modulating signal m(t). in Theff
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Q5. (a) (b) (c) Describe the algorithmic steps to compute the Short Time Fourier Transform 3 marks An alarm is recorded at 10 kHz sampling frequency. It is composed of two tones, one at 1.5kHz and one at 1.7kHz. The two tones alternate every 0.2 seconds. What window size would you use to resolve the two components in a Spectrogram? 3 marks Two airplanes are entering in a controlled airspace at two different speeds. Airplane A approaches at 70 m/s while airplane B approaches at 62 m/s. What is the minimum number of pulses that an air traffic control radar working at a carrier frequency of 1.2 GHz and a PRF of 1200 Hz should use to discriminate in Doppler the two airplanes? 7 marks A UAV is approaching a dam on which a metallic reflector is installed. Due to the water motion the dam vibrates at 4 Hz with a displacement of the reflector of 0.04 m in each direction. Sketch the micro-Doppler that the UAV will measure if it stops in front of the metallic reflector and observes it with a 24 GHz radar. 7 marks (d)
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Question 4 25 pts (A) Consider a periodic signal xi(t) with fundamental period T=4, whose waveform over one period is expressed as X1(t) t, 0
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3. A 460V, 25hp, 60Hz, 4 pole, Y-connected induction motor has the following impedances in ohms per phase referred to the stator circuit: R1 = 0.641 R2 0.332 X1 = 1.106 X2 = 0.464 Xm = 26.3 The total rotational losses are 1100W and are assumed to be constant. The core loss is lumped in with the rotational losses. For a rotor slip of 2.2% at the rated voltage and rated frequency, find the motor's a) speed b) stator current c) power factor d) Pconv and Pout e) nd and 1oad f) efficiency
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3. A three-phase, Y-connected, 575 V (line-line, RMS), 50 kW, 60 Hz, 6-pole induction motor has the following equivalent-circuit parameters in ohms-per-phase referred to the stator: R1 = 0.05 R2 = 0.1 X1 = 0.75 X2 = 0.75 Xm = 100 Slip = 1% Please answer the following questions. (40 pts) (a) Draw the single-phase equivalent circuit for the induction machine. (b) Calculate the machine speed in unit of RPM. (c) Calculate the rotor side current. (d) Calculate the gap power, mechanical power, and rotor-loss power. (e) Calculate the torque at this slip.
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b) A three-phase overhead line has a load of 30MW, the line voltage is 33kV and power factor is 0.85 lagging. The receiving end has a synchronous compensator, 33kV is maintained at both ends of the line. Calculate the MVAr of the compensator given that the line resistance is 6.50 per phase and inductance reactance is 2002 per phase. (6 Marks)
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10. State Space representations: (10 pts ea) a. Determine a state space representation of the following differential equation: +6 +12y + 32y = 3 + 10u b. Determine the transfer function for the following state-space system: 1-2 x = 1 2 1 2 1 x + (ou 3 y = [ 21]x
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Consider the signal 0tT s(t) = [(A/T)t cos 2 fet 10 otherwise 1. Determine the impulse response of the matched filter for the signal. 2. Determine the output of the matched filter at t = T. 3. Suppose the signal s(t) is passed through a correlator that correlates the input s(t) with s(t). Determine the value of the correlator output at t = T. Compare your result with that in part 2.
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Question 2 [4] A 4-pole DC machine, having wave-wound armature winding has 55 slots, each slot containing 19 conductors. What will be the voltage generated in the machine when driven at 1500 r/min assuming the flux per pole is 3 mWb? (4) Final answer Page Acro
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(a) Using neat diagrams of the output power for a resistive load, explain why single phase generators will cause vibrations in a wind turbine and why these vibrations do not occur when using three phase generators. (
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Part B Task 3 a. Write a matlab code to design a chirp signal x(n) which has frequency, 700 Hz at 0 seconds and reaches 1.5kHz by end of 10th second. Assume sampling frequency of 8kHz. (7 Marks) b. Design an IIR filter to have a notch at 1kHz using fdatool. (7 Marks) c. Plot the spectrum of signal before and after filtering on a scale - to . Observe the plot and comment on the range of peaks from the plot. (10 Marks) (5 Marks) d. Critically analyze the design specification. e. Demonstrate the working of filter by producing sound before and after filtering using (6 Marks) necessary functions. Task 4:
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An op amp designed to have a low-frequency gain of 10^4 VN and a high-frequency response dominated by a single pole at 1000 rad/s acquires, through a manufacturing error, a pair of additional poles at 100,000 rad/s. Assume that the total phase shift of the open-loop gain A reaches 1800 at 10^5 rad/s (that is w180 = 10^5 rad/s). At this frequency, for what value of , assumed to be frequency independent, does the loop gain at w = w180 reach a value of unity? That is, find the largest feedback factor allowed, Ber. = a. 0.01 O b. 0.05 O c. 0.02 O d. 0.033
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EXAMPLE 4.3 The 440 V, 50Hz, 3-phase 4-wire main to a workshop provides power for the following loads. (a) Three 3 kW induction motors each 3-phase, 85 per cent efficient, and operat- ing at a lagging power factor of 0-9. (b) Two single-phase electric furnaces of 250 V rating each consuming 6kW at unity power factor. () A general lighting load of 3kW, 250 Y at unity power factor. If the lighting load is connected between one phase and neutral, while the fummaces are connected one between each of the other phases and neutral, calculate the current in each line and the neutral current at full load. (H.N.C.)
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(a) A 3-phase, 15kW, 400V, 50Hz, 6-pole, delta connected squirrel cage induction motor has a full-load efficiency of 89%, power factor of 0.87 lagging, and running speed of 970 rpm. Calculate the following for full-load conditions; (i) Input power (VA) (3 Marks) (ii) Supply Line current (3 Marks) (iii) Phase current (3 Marks) (iv) Full-load torque (3 Marks) (b) A three phase induction motor has winding impedances of 20. The motor terminal box contains six terminals, two for each winding. Explain how the starting line currents of this motor can be reduced and calculate these line currents when the motor is powered using 400V 50Hz three phase supply. Assume line currents are determined only by the winding impedance value
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a given finite state machine has an input, w, and an output, z. during four consecutive clock pulses, a sequence of four values of the w signal is applied. derive a state table for the finite state machine that produces z = 1 when it detects that either the sequence w : 1010 or w : 1110 has been applied; otherwise, z = 0. after the fifth clock pulse as one state is required to hold the output, the machine has to be again in the reset state, ready for the next sequence. minimize the number of states needed.
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1. A 3 phase, overhead transmission line has a total series impedance per phase of 200 ohms and a total shunt admittance of 0.0013 siemens per phase. The line delivers a load of 80 MW at a 0.8 pf lagging and 220 kV between the lines. Determine the sending end line voltage and current by Rigorous method. 2. Obtain the symmetrical components of a set of unbalanced currents: IA = 1.6 225 IB = 1.0 2180 Ic = 0.9 2132 3. Given Vo = 3.5 4122, V = 5.0 - 10, V = 1.9 292, find the phase sequence components V, VB and Vc. 4. The following are the symmetrical components of phase B current. Positive sequence component = 10 cis (45) Negative sequence component 20 cis (-30) 0.5 + j0.9 Zero-sequence component Determine the positive-sequence component of phase A.
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Problem 2.0 (25 Points) (0) Draw the circuit diagram of 8 bit digital to analog (D/A) converter using switches. What are the differences between SRAM and DRAM? Why SRAM is called static and DRAM is called dynamic?
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Problem 3.0 (25 Points) Write down the VHDL code of MOD-8 down counter.
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Question 1 A 25kW, 250V dc shunt machine has armature and field resistances of 0.069 and 100respectfully. The machine is first operated as a generator then as a motor. Determine: a. the generated emf when operated as a generator delivering 25kW output b. the power developed when operated as a generator delivering 25kW output c. the back emf when operated as a motor drawing 25kW input power d. the power developed when operated as a motor drawing 25kW input power
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