What is Power: Definition and 999 Discussions

A power outage (also called a power cut, a power out, a power blackout, a power failure, a power loss, or a blackout) is the loss of the electrical power network supply to an end user.There are many causes of power failures in an electricity network. Examples of these causes include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, cascading failure, fuse or circuit breaker operation.
Power failures are particularly critical at sites where the environment and public safety are at risk. Institutions such as hospitals, sewage treatment plants, and mines will usually have backup power sources such as standby generators, which will automatically start up when electrical power is lost. Other critical systems, such as telecommunication, are also required to have emergency power. The battery room of a telephone exchange usually has arrays of lead–acid batteries for backup and also a socket for connecting a generator during extended periods of outage.

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  1. C

    What speed v(t) enables constant power by release compressed spring?

    We know linear spring force F = kx(t), k = spring constant, during any moment t of energy release. displacement x(t) = ʃv(t)dt the power p = F*V = kx(t)v(t)= kv(t)* ʃv(t)dt My question: Is there a mathematical function of special v(t) to make power p constant?
  2. M

    Heat pump efficiency calculations - Compressor power issue

    The heat pump comprises of the 4 components: evaporator, compressor, condenser and expansion valve. Thermal power required to heat the building: 12.1 kW at condensing temperature tc = 44.3 deg C For the evaporator: vaporizing temperature tv = -7 deg C Subcooling temperature for the heat pump Δ...
  3. hquang001

    Which Formula Should I Use for Calculating Power in an AC Circuit?

    Should i use P = V.I or P = Vrms.Irms.cosφ ?
  4. C

    What's different in a transformer core when coupling high & low power?

    This is one of those 'oh, I am not sure I know the answer' kind of thoughts. The strength of magnetic flux in a transformer core is a function of volts per turn, Faraday figured that one out. So, if I have a light load on a secondary (let's say it is pure ohmic for now, let's not confuse it)...
  5. W

    Power to keep helicopter hovering

    My thinking was that the power produced by a falling object is P=Fv=(-mg)(-gt)=mg^2t. So it depends on t, ie the "counter power" must also depend on t if it is to balance it, right? But author's solution is a constant. I know I am making a mistake somewhere. Note: Apologies for the lack of...
  6. PainterGuy

    Calculating the nth power of a matrix

    Mentor note: Since the technique used here involves differentiation, I moved this to the Calculus section. Hi, I was trying to do the problem below. I was following the approach presented in this answer. I assume the approach is correct. The answer I ended up with is clearly wrong. Where am I...
  7. L

    A Can falling factorials be a Schauder basis for formal power series?

    We usually talk about ##F[[x]]##, the set of formal power series with coefficients in ##F##, as a topological ring. But we can also view it as a topological vector space over ##F## where ##F## is endowed with the discrete topology. And viewed in this way, ##\{x^n:n\in\mathbb{N}\}## is a...
  8. L

    Electrical Machines and Power Flow

    I have been studying the representation of generators in power flow studies and I would appreciate your comments in this thread. From the book Fitzgerald & Kingsley's Electric Machinery, I understand that there are unsaturated and saturated reactances. In section 5.3.2 of the book it is said...
  9. W

    What is the force equation for power from a trolley motor?

    Author solution:
  10. Bix

    Why Does Calculating Train Engine Power Result in Different Values?

    How did you find PF?: Online [Thread moved from the New Member Intro forum, so no Schoolwork Template is shown] Hi. I'm new and am trying to solve a simple question 'Find the max power of a train engine traveling level at 50 metres per second if total resistance to motion is 30 KiloNewtons...
  11. I

    What is "Apparent Power" (VA)?

    In school I learned about impedance: where.. $$Z^2 = R^2 + X_{net}^2$$ but this was the only triangle I recall learning about. The picture below I definitely do not recall. from this Link The only quantity I am familiar with is the x-axis (Power). If someone could explain...
  12. J

    Find the power of a man running (work and potential energy)

    I started of by trying to find the work for I got stuck because I did not know how to solve for the Force. I solved for the distance by doing 3=d/5s which gave me 15m. but then I couldn't figure out where to go next in the problem because I don't know how to solve for (f) so an explanation would...
  13. H

    Why I*ε Cannot be Used to Calculate Power

    Why can't we calculate use I*ε to obtain the power?
  14. F

    Air-Gap & Wireless Power Transmission Efficiency

    Summary:: How does the air-gap affect the efficiency ? For a wireless power transmission system, to what extend does the efficiency and coupling parameters get affected by the distance between the coils? What can be done to increase the power transmission or efficiency regardless of the value...
  15. H

    The greatest power will be dissipated in the resistor if R =?

    Since the power generated by both primary coil and secondary coil would be the same in a transformer, so I used the relationships stated above to deduce the resistance R in secondary coil. P1 = N2^2 *100 = 100^2 * 100 P2 = N1^2 *100 = 500^2 * R R = 4 Let me know if my thoughts here are...
  16. H

    What is the power factor in a series circuit?

    I calculated in the following and got the correct answer. However, I wonder whether this way is correct or not. Thanks! PR / Pavg = Irms^2 * R / Irms^2*Z = 15 /33.36 = 0.45
  17. B

    Calculate the amount of torque and power needed on an inclined plane

    I have calculated the force equation on the x-plane which is f - mgsin(30) - friction force = ma and from the equation vf = vi + at resulting a = v/10
  18. M

    Lectro Power Saver Review: $30 Plug-In Electricity Savings

    Has anyone reviewed the Lectro Saver -Electricity Saving Box. Its a $30 plug in gadget that claims to smooth out incoming power and use it more efficiently so that your energy bills are drastically reduced, They claim it is inspired by Nikola Tesla.!
  19. D

    Designing a Power Transformer: Tips and Techniques

    We need all the project including all details with schema, If you are talented for drawing the project, please contact me. 50/62,5 MVA, 154/33 kVA
  20. jim mcnamara

    What can we learn from Texas' power grid failure?

    https://www.nbcnews.com/science/environment/one-texas-storm-exposed-energy-grid-unprepared-climate-change-rcna289 The link above is an opinion piece that discusses the possible lessons from the experience in Texas. FYI: This was a textbook system wide grid failure, caused by off the charts...
  21. V

    Handle Peak Inrush Current of a BLDC Motor to protect the Power Supply

    I have to use a BLDC motor combined with a BLDC motor driver (X-NUCLEO-IHM08M1) The motor has a rated current of 7.3A. So i am planning to use a 36VDC 13.9A power supply (SMPS). The problem is that the PS that i want to use has a "HICCUP mode" for overload protection and not a "constant current...
  22. J

    Securing Power from a 120VAC Generator: H3 and H8 Taps

    My plan is to power the secondary with my 120VAC generator and use the 240VAC primary connection configuration and use the H3 and H8 taps as the neutral.
  23. jjson775

    Power of black body radiation at 1.00 nm

  24. anorlunda

    Grim Day on the Texas Power Grid

    This is an enormous failure, comparable to the "Great Northeast Blackout of 1965". Rolling blackouts are being imposed at a time when millions of residential customers need home heating. The oil refineries shut down. Expect gasoline/diesel shortages and price spikes nation wide in a few days...
  25. A

    Resistive heating power AC vs rectified AC/DC

    I thought about this for some time but I can't seem to really understand the cause. Now I remember some time ago using a transformer for my self made soldering iron, I wound it to have the right temperature at about 45 VAC input but I guess I missed a bit , so that when I connected it to the 45...
  26. PhysicsTest

    Calculating Average Power and Energy Consumption for a Heater

    The v(t) = 120##\sqrt(2)\sin(2\pi 60t)##. Let the resistance of the heater be "R", then the rated power = 1500W. The rated power is the average power 1500 = ##\frac{120^2 *5 * 60} {12*60 * R} ## ->eq1 R = 4 Ohm. a. Instantaneous power is ##P = \frac{v^2} R ## -> eq2 ##P =...
  27. K

    Questions on operating a nuclear power plant on the Moon or Mars

    Heat cannot be removed by liquid-to-gas heat exchangers since there is no substantial atmospheres on the Moon or on Mars. It cannot be dissipated by venting steam since there is a critical water shortage. It cannot be dissipated by rocks or soil since both are essentially thermal insulators. It...
  28. L

    Alternating current and Average power

    For a current i(t)=I_0\sin(\omega t+\varphi_0) period is ##T=\frac{2\pi}{\omega}##, Power is defined as p(t)=Ri^2(t). So period of power is not any more ##T=\frac{2\pi}{\omega}##. Why then average power is P=\frac{1}{T}\int^T_0p(t)d t. Why are we using the period of current and not of the...
  29. A

    Determining the maximum braking power using derivations

    Hello! So what I've tried to tackle this problem is derive the equation,set it equal to zero,find a value for v and than put it in the second derivation.So when I derive this I get $$ \frac{v^2+9-v *(2v)}{v^4+8v^2+16)} $$ Now if i set that equal 0 and try to find a value for v I get this. ##...
  30. PhysicsTest

    Power calculations of AC signal

    The below are the formulas i have seen from the book, but no particular formula for the peak power Instantaneous power ##p(t) = v(t) i(t) W## ->eq1 Average power ##p(t)_{avg} = \frac{\int_{t_0}^{t_0+T} p(t)dt} T W## ->eq2 a. Instantaneous power ##v(t) =A\sin(\omega t)## ->eq3 ##i(t) =...
  31. bardia sepehrnia

    Engineering Calculating Power Factor in an AC circuit, given voltage and current

    My attempt at solving this question: I realized my attempt is wrong however I just don't know how to proceed in the first step. How can I calculate the phase shift? and find Voltage and Current in phasor form??If I know that, then I can use power factor formula: pf=Pav/V*I
  32. N

    Electrical Unconnected wall wart power consumption

    Hi. Not homework. I left that behind me 40yrs ago:) How much power (if any) does a plugged in but unconnected wall wart (transformer/rectifier) consume? Eg. I have a phone charger labelled as: Input: 100-240V~50/60Hz 0.3A. ____________ Output: 5V - - - -...
  33. P

    Engineering Small signal AC modeling for a boost converter with resistive losses

    I've attached my attempts at the solution and the actual question below. I believe the only issue I am having is I don't know how to get rid of "I" in both my final inductor and capacitor equations as the HW states I shouldn't have anything in term of I. I believe I need to put "I" in terms of...
  34. Doma Noemi

    Electricity in the human body -- Is there enough to power a prosthesis?

    Can we use the electricity from the muscle to power an engine (like a prosthesis)?
  35. ghowriter

    How to make a custom UPS using an old PC power supply and 18650 batteries?

    Yes, this is a question. I already converted an old PC power supply (350 Watt) to replace the bower bricks for my Internet modem and router. What I would like to do now is install a 2-3 hour mini-UPS in the mix so I can remove it from my computer's UPS. I have spent days online scouring the web...
  36. R

    Power Line Losses: Trivial Problem, Confusing Answer

    This problem is trivial, but I cannot make sense of my answer (I am not even going to bother with the cost calculation. First, I used P=IV with P=15 MW and V=120 V to find I=125 kA So far so good. Then I calculated the resistance per meter as R=\rho\ell/A=(1.68\times 10^8\Omega\cdot...
  37. Ntip

    Capacitor type selection for power converter

    I am looking at capacitor selection for a switched capacitor converter and I'm not sure which voltage rating to look for. I've was going to consider the DC rating since they're holding off a DC voltage, but they are subject to PWM excitation since they're switching between nodes at different...
  38. S

    Carrying capacity of power grids - USA and others

    If some technology (such as versions of fusion power) makes generating electric power vastly cheaper, will it be necessary and expensive to increase the capacity of current power grids in the USA and other countries? Or is it the case that current power grids have a lot of excess transmission...
  39. S

    I Extremums of functions: x to the power of x to the power of a

    I plotted the x(red dots) coordinates and y coordinates( black dots) of extremums of functions x^x^a (the x coordinate of the dots is a and y coordinate of the dots is x or y coordinate of the extremum). Is there a function, on which are located all the black dots or all the red dots? P.S. The...
  40. P

    Find the power needed to accelerate this elevator downward

    An elevator of mass M is accelerating downward with constant acceleration A. Friction force acting on the elevator is constant and given by f (The initial speed of the elevator is zero.). Find the power generated by the engine of the elevator (in terms of M, A, g, f, and time t). For this...
  41. mcastillo356

    B Limit of a function raised to a fractional power

    Hi, PF This is the quote: "If ##m## is an integer and ##n## is a positive integer, then 6. Limit of a power: ## \displaystyle\lim_{x \to{a}}{\left[f(x)\right]^{m/n}} ## whenever ##L>0## if ##n## is even, and ##L\neq{0}## if ##m<0##" What do I understand? -whenever ##L>0## if ##n## is even: ##m##...
  42. P

    Is 532nm the Optimum Wavelength for Atmospheric Particle Tracking?

    In reading scientific papers on atmospheric pulsed Lidars there is often a table that includes system information such as the type of laser, the power in uJ or mJ and the rep rate. Examples of the power would be usually somewhere between 50 uJ and 30 mJ. Rep rates are between 10 and 10,000...
  43. S

    Converting a Lawn Tractor to Electric Power

    So I am converting an old gas lawn tractor to electric. I have a 48v 2000w motor to drive the axle. For the deck, I sourced two 40v old Ryobi deck motors (I don't have them yet). Since my power supply will be a 48v lithium battery, I wanted to run the two deck motors off the controller running...
  44. icesalmon

    Engineering Find the Average Power absorbed by the 20k Resistor

    I wrote the following equations using node voltage, my issue is that I'm confused about why the RC branch at the output doesn't effect the value of the Gain for the amplifier; the equation involving VA / ( 20k - j12k ) is omitted in the solution. IAC = IAB + IBC V- = V+ = VB = VS ( VA-VC...
  45. P

    Coaxial cable - capacitance, leakage current and power lost

    Could somebody check my solution?
  46. PhysicsTest

    Power calculations for an AC network

    The voltage and current are given as ##v(t) = 359.3\sin(\omega t + 15) volts ## and current is ## i(t) = 100\cos(\omega t + 5) ##. My question here is do i need to convert the voltage into cos terms or current into sin terms. suppose if i convert the voltage into cos terms, the calculations will...
  47. PhysicsTest

    Power Calculation of general electric circuit

    I am trying to calculate the power calculation of a general circuit with voltage leading the current by a phase difference of ##\theta##. The instantaneous voltage is given by ##v = V_m\sin(\omega t +\theta) ; i = I_m\sin(\omega t) ##. The instantaneous power is then ##p = V_m I_m \sin(\omega t...
  48. S

    Piston Engine versus Jet Engine Power

    Hello All The power output of piston engines fitted to aircraft were (and still are?) specified in terms of their HP rating, whereas jet engines are typically rated in terms of their trust. For example, a Mosquito two engined fighter/bomber was equipped with two Merlins, each producing...
  49. PhysicsTest

    Static power bridge motor drive circuit

    I am referring to the application note from TI, the below is the power bridge circuit. The truth table is as below a. I try the first values of A=0, B=0, C=0 the circuit would then become like this according to me It is open above point O, then how the voltage of ##\frac{-V_{DC}} 2## will be...
  50. B

    Chiller power consumption calculation

    Hello, If I am trying to calculate the heat removed from a chiller system through this formula on engineering toolbox.com: Does COP or efficiency of the equipment come into play with this calculation? For example if a chiller is fully loaded isn't it running more efficient for a watt/ton...
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