Explore BrainMass

Power Engineering

Power engineering is a subfield of electrical engineering that looks at the transmission and distribution of electric power and the electrical devices connected to such systems such as, generators, motors and transformers. Many fields are concerned with the problems of three-phase AC power; the standard for large-scale power transmission and distribution across the modern world.

Electric power is the mathematical product of two quantities: current and voltage. These quantities can vary with respect to time (AC) or they can be kept at a constant level (DC). Most refrigerators, air conditioners, pumps and industrial machinery use AC power; whereas digital equipment uses DC power. AC power has the benefit of being easy to transform between voltages and is able to be generated and utilised by brushless machinery. DC power remains the practical choice in digital systems and can be more economical to transmit over long distances at high voltages.

Power engineering looks at the generation, transmission and distribution of electricity and the design of a range of related devices. These include transformers, electric generators, electric motors and power electronics. Power engineers also work on systems that do not connect to the grid. These systems are called off-grid power systems and may be used in preference to on-grid systems for a variety of reasons. 

Relaibility analysis Normal Distribution &Lognormal distribution

1. Five percent of a certain grade of tires wear our before 25,000 miles, and another 5 percent of tires exceed 35,000 miles. Determine the tire reliability at 24,000 miles if wearout is normally distributed. 2. The wearout of a machine part has a lognormal distribution with s=0.5 and t_med=5,630 hours. What is MTTF?

DC power supply design

Q1. A 9 V power supply delivers 2 A to a resistive load. The a.c. supply is 230 V, 50 Hz and a bridge rectifier is used in conjunction with a 0. 047 farad reservoir capacitor. Estimate: (a) The peak-to-peak ripple voltage. (b) The transformer secondary voltage if the total forward voltage drop in the rectifier is 2 V at 2 A.

Oscillators including Armstrong Oscillator

See attachment for diagrams. 1. With reference to the block diagram of FIGURE 1, state the two conditions that must be satisfied to give an oscillatory output. FIG. 1 2. With reference to the block diagram of FIGURE 1, determine the required value of G to give an oscillatory output if H = -10 dB. 3. FIGURE 2 shows a p

Fourier Analysis of Time domain waveform using Excel and THD

Attached are images for questions regarding Fourier Analysis. Q3. Preamble Techniques involving the electronic control of power to a load such as controlled rectification and variable frequency drives are widely used by industry. There can be, however, serious problems with these techniques because of the generation of har

Power Systems Theory Definitions and Formulas

Hi there, I need some help in these define and state questions Define (a) The fault level of a system or unit in a system (b) base MVA State (c) the equation for percentage impedance or impedance voltage (d) the relationship between X% and Xpu (e) the units of X% and Xpu (f) Xpu in terms of the fault level MVA and th

Electrical Supply and Distribution Systems

Attached are some examples of the questions I am working through, could you please give fully explained and worked out answers as previous help given and indicate the number of credits that would be sufficient.

Complex Waveforms / Harmonic Distortion

Please find attached files for examples of Complex Waveform, Power Circuits and Harmonic Distortion, and Fourier Series. Please show all calculations in full with answers Please give fully worked out explanations and answers and graphical representations where required. Please note I have added 2 XL spreadsheets for addit

Single Phase Circuit

A resistor and a capacitor are connected in series across a 150 V a.c supply. When the frequency is 40 Hz the current is 5 A, and when the frequency is 50 Hz the current is 6 A. Find the resistance and capacitance of the resistor and capacitor respectively. If they are now connected in parallel across the 150 V supply, find t

Two Port Network is used to model the transmission line.

Note: The Solution is handwritten. FIGURE 3(a) represents a 50 Hz, three-phase, high-voltage, transmission line. For one phase, the relationships between the sending end voltage and current and the receiving end voltage are given by the complex ABCD equations: where VS is the sending-end voltage, IS the sending-end current

Interpreting frequency domain signal spectrum to time domain

A spectrum analyzer is connected to an unknown signal. The spectrum analyzer displays the voltage level of signals in volts vertically and frequency horizontally. The spectrum of the unknown signal creates the following display: A vertical line at a frequency of 50 kHz with a magnitude of 1.80 V A vertical line at a fr

Transformer Winding Regulation

A 415V to 11 kV transformer has a rating of 200 kVA. The winding resistance and leakage reactance when referred to the primary are 0.014 and 0.057 ohms respectively. (a) Determine the % regulation of the transformer at 0.8 power factor lagging. (b) In designing a particular 415V to 11 kV, 200 kVA transformer, the primary w

Frequency modulation

1. What type of signal is represented by the code 15A3? 2. Briefly explain the difference between phase and frequency modulation. 3. A 15 mV sinusoid with input frequency 450 Hz is applied to an FM generator with k = 1000 Hz/20 mV. Find the positive frequency deviation. 4. An FM signal is given by e = 40 sin (2Æ'Ã? ~106t

Solutions of posed Qs on ADC, Sampling and Transmission

An audio signal has frequencies between 100 Hz and 12 kHz. It is sampled and converted to a digital bit stream using an 8 bit A/D converter. The digital signal is sent to a receiver that converts the signal back to its original analog form. a. Calculate the lowest sampling frequency that can be used in practice. b.

Find the power dissipated.

A signal generator outputs a sine wave signal with a frequency of 1000 Hz and an rms voltage of 20.0 V. The output of the spectrum analyzer is connected to a 200 ohm resistor. a. What is the power dissipated in the 200 ohm resistor in watts, in dBW, and in dBm? b. An amplifier with a gain of 15 dB over the frequency ra

RMS current, Power dissipated, Resonant frequency

A circuit consists of a sine wave signal generator and a reactive component (L or C). The output of the generator is a sine wave with a peak amplitude of 8.8 volts at a frequency of 10.0 kHz. a. The generator is connected to an inductor with L = 10.0 mH. What is the rms current flowing in the inductor? b. The generator

Spectrum Analyzer: Signal Waveforms

A spectrum analyzer is connected to an unknown signal. The spectrum analyzer displays the power level of signals in dBm vertically and frequency horizontally. The spectrum of the unknown signal creates the following display: A vertical line at -6 dBm at 0 Hz (DC), A vertical line at a frequency of 10 kHz with a power level

Analysing an RF splitter and power levels

A splitter is a device that has a single input and several outputs. It is used to send a signal to several different locations. For example, your apartment or house might have cable TV that delivers a wideband signal via a coaxial cable. A splitter can be used to send the same signal to different rooms so that individual TV se

Received power of half-wave dipole antennas

Assume that two antennas are half-wave dipoles and each has a directive gain of 3dB. If the transmitted power is 1W and the two antennas are separated by a distance of 10 km, what is the received power? Assume that the antennas are aligned so that the directive gain numbers are correct and that the frequency used is 100 MHz.

Public Address system howling, Resolution of ADC, Power delivered to the heating system, Power in the load of thyristor circuit, Hydraulic press controlled by a solenoid-operated control valve

Please refer to the attachment for mentioned figures. 2. FIGURE 5 shows a public address (P.A.) system. (a) Represent the P.A. system as an `information system' block diagram. (b) It is found that if the microphone is brought into the proximity of the loudspeaker, the system will `howl'. Carefully explain, making reference

Find the maximum power transfer and resistors in attenuator pads.

1. Find (a) RL for maximum power transfer, and (b) the maximum power transferred to the load 2. Design a pi-section symmetrical attenuator pad to provide a voltage attenuation of 12dB with a characteristic impedance of 600 ohms. 3. Using the Delta-Star transformation, obtain the equivalent T -section symmetrical attenuator

Basic electricity - 3 phase installation powered

Consider the following: A 3 phase installation powered by 400V 50Hz is composed of 6 machines. (Please see the attached table) Find: a) Total apparent power b) Total absorbed current (line current) c) Installation power factor d) The power of the capacitors that should be installed to have a power factor of 0.95 e) Tot

Power factor in AC circuit

A single phase electric motor has an output power of 10 kW and an efficiency of 90% at full load. The motor is fed from a 240 V supply via a cable that has a resistance of 10 milli ohms per metre length. If the terminal voltage to the motor must not fall below 90% of the supply voltage, calculate the maximum return length of the

Problem Feeder - Transformer

A single-phase load is supplied through a 35 kV feeder whose impedance is 115 + j380 Ohms and a 35 kV, 2400 V transformer whose equivalent impedance is 0.26 + j1.21 Ohms referred to its low voltage side. The load is 180 kW at 0.87 leading power factor and 2320 V. (a) Compute the voltage at high-voltage terminals of the

Power Factor Correction

Three parallel impedances in rectangular form as follows: 8.66+j5 ohm , 25+j0 ohm , 3.54+j2.54. A 240 volt 50 Hz supply Calculate overall power factor of the three loads.


Prior to t=0, a 100- uF capacitance is uncharged. Starting at t=0, the voltage across the capacitor is increased linearly with time to 100V in 2s. Then, the voltage remains constant at 100V. Sketch the voltage, current, power, and stored energy to scale versus time. Please show equations for the sketches.