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Questions tagged [power]

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Converting string vibration to electricity

Is there a device that can use the energy from a vibrating string (i.e. guitar string, etc.) to produce enough electricity to power a small LED?
Matthias's user avatar
0 votes
0 answers
27 views

What is the best way to keep an abandoned facility running with no external power?

I asked a question here about using a waterwheel and an Archemedes screw to keep at least the water running in an abandoned facility. The one answer I got so far seemed to imply that wouldn't actually ...
user avatar
0 votes
1 answer
58 views

Is exceeding the maximum power an issue for solar panels and inverters?

Say I have a solar panel setup which can produce a total of 16 kW peak. With an inverter that has a maximum PV input of 6kW, would this be an issue that could lead to defects? Or is it just ...
arminb's user avatar
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0 votes
1 answer
49 views

Explanation of phases of fridge cycle from power draw (power factor, reactive and active power)

I've got this power draw graph of my fridge during a couple of cycles. The power factor axis is on the left, active and reactive power axis in watts/VAr on the right. I'd like to understand the phases ...
JavierG's user avatar
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1 answer
54 views

How do AC servos have constant torque region?

I have been learning about AC servos for a project. As i look through the torque speed curves, I get stuck. I understand how to use them, but I am baffled by the shape. I was always taught that there ...
DanielPatrick's user avatar
1 vote
0 answers
51 views

How to calculate Power Factor capacitors for welder

I have a 200 Amp AC welder and I am trying to figure out what the power factor correction capacitor should be. I ran some numbers but they do not sound right and I was wondering if I anybody could ...
user1683793's user avatar
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4 answers
140 views

Compressed air instead of steam in a steam engine, would that allow powered flight?

My understanding is that regular steam engines could use instead compressed air (not sure what had to be done to allow this) and if so, would not such an arrangement, which did not require fuel and ...
releseabe's user avatar
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1 answer
42 views

Converting RMS to Maximum Power

If I have a sinusoidal voltage signal of amplitude $V_m$ driving a resistance $R$, what is the relationship between the RMS power $P_{rms}$ and the maximum power $P_{max}$ delivered to the resistance? ...
PikaPika's user avatar
-1 votes
2 answers
47 views

Charger not charging phone at advertised power, why?

First of all I understand there are so many variables so I'm going to try to be as explicit as possible: I have various chargers which state they can deliver 3A @ 5V I have an iPhone 12 Pro Max (I am ...
QuantumBlack's user avatar
0 votes
2 answers
182 views

Flywheel power vs. Gross power in bulldozers

In product specifications of bulldozers, the manufacturers give several figures for the engine power, such as flywheel power, net power - Net SAE J1349/ISO 9249, ISO 14396 power, and Gross SAE J1995 ...
Triceratops's user avatar
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1 answer
36 views

Calculate constant power applied to displace a mass a given distance within a given time

I'm trying to determine electric motor power sizing with requirements given for covering a particular distance within a certain time. The knowns are the vehicle mass, the allotted time, the target ...
KevinGrumble's user avatar
3 votes
4 answers
169 views

Why do kWh (smart) meters have a maximum operating altitude?

At first I thought it was a bad translation from Chinese to English, but it turns out that many data-sheets of kWh power meters mention a maximum altitude, usually below 2 or 3 km. For example: ...
Louis Somers's user avatar
0 votes
2 answers
227 views

Calculating the power of a rotor using two methods

I have been calculating the power required to accelerate a small solid rotor up to 2000 RPM using two different but equally valid methods of calculation, and yet they give different results by a ...
Julian Perry's user avatar
0 votes
0 answers
79 views

Can I use the same USB C to power and program a Raspberry Pi CM4?

I'm currently making a RP CM4 breakout board and I want to use a single USB-C to upload the OS and power it. To achieve this I made the following PCB: With this setup I could also plug in a USB drive ...
Illés Balog's user avatar
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0 answers
20 views

How can I calculate power dissipating through a Eaton moulded circuit breaker?

Excuse my English. I am trying to figure out how to calculate the power dissipating through a CB by Eaton. Not much info is given on resistance. Assuming I selected a 250 CB, how can I calculate the ...
Eaglesea Kim's user avatar
1 vote
2 answers
250 views

What will be the destiny of the oxygen gas created in the future hydrogen economy?

When I was recently studying biomass-to-electricity (gasification methods, Drax power station...), I was wondering whether the efficiencies of these systems would not benefit from a source of pure ...
5th decile's user avatar
0 votes
1 answer
37 views

Wind triboelectricity shakers in series

I've seen shaker generators made with small plastic hemispheres with aluminum foil stuck on inside both, and a small ball wrapped in tape put in and sealed up. Then the shaker is vibrated and it ...
El Flea's user avatar
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0 answers
46 views

Would a modern mercury vapor / steam combined rankine cycle be more efficient than a steam only cycle?

During the first half of the 20th century mercury vapor turbines were in use in commercial power stations. The mercury vapor was the working fluid for a high temperature Rankine cycle and the mercury ...
JanKanis's user avatar
  • 254
0 votes
1 answer
35 views

What properties are most important for a fluid in the generation of steam power?

I was curious if water is the most efficient fluid for use in generating steam power. I thought it might be, since it has the highest latent heat of evaporation of any fluid. I wasn't sure if other ...
user27657's user avatar
1 vote
1 answer
266 views

Can over correcting power factor cause damage to equipment?

If you over-correct your power factor, that is your power factor is leading, not lagging as expected by the utility, can you damage your (as opposed to the utility's) equipment? As we are all aware, ...
user1683793's user avatar
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0 votes
1 answer
117 views

how to plot power output graph for motors

What is the best way to plot motor power output graphs? Does anyone know how we can plot this graph for motors and engines?
Vinoth Kumar's user avatar
0 votes
0 answers
25 views

How is it possible to mount this PSU for 19' rack?

As a part of a project I need to deliver all hardware as 2x 19" Racks. One components of the hardware is two of these power supplies. Can these supplies be fit/mounted on 19" Racks in a way? ...
user1245's user avatar
  • 101
1 vote
0 answers
650 views

Standards for the sign of the power factor; IEC and IEEE; is there an ANSI standard?

Working with some power factor measurement, this article (reference: https://www.se.com/ww/en/faqs/FA212521/) has this interesting bit: Issue: Understanding and interpreting the sign of a power factor ...
asylumax's user avatar
  • 181
0 votes
2 answers
48 views

Squared telecom parameters

I observe that some telecommunication parameters are squared like noise power is $σ^2=-95\text{ dBm}$, and the amplifier coefficient $η^2=20\text{ dB}$. What is the meaning of the square? Can I remove ...
Mary Dona's user avatar
0 votes
0 answers
36 views

Peculiar step-down transformer behavior

I have wired several loaded transformers and when calculating power on H vs X side by multiplying current times voltage the wattage is not even close to equal with the H side having 2 to 3 times more ...
ZipStein's user avatar
0 votes
1 answer
53 views

mg996r - maximum weight for robot arm [closed]

I want to build a robot arm (see https://youtu.be/F0ZvF-FbCr0) to move a dumbbell of 2 kg (roughly 2.2 lbs). However, since I have no background in engineering, I have no idea how to calculate / find ...
juliusphysics's user avatar
0 votes
0 answers
35 views

How to estimate needed spindle power for lathe/mill?

I'm trying to understand how much spindle power is needed for machining various kinds of metal. I assume that as depth of cut and surface speed go up that it will cause the required spindle power to ...
Jake's user avatar
  • 103
0 votes
1 answer
98 views

Calculate uphill efficiency on different gears

I was interested to find whether it would be more efficient to climb a hill on a lower gear, so I did some calculations. I have the following data of a custom vehicle: Gear Drive force (N) Max speed (...
php_nub_qq's user avatar
2 votes
2 answers
256 views

Torque Problems vs Motor Problem?

I want to preface this by saying I am software engineer so each part of this robot build has been a lesson on its own. From welding, to CAD design, pillow block bearings, etc, etc.... I am working ...
Sam Hammamy's user avatar
1 vote
1 answer
61 views

Why do identical-looking power plugs randomly not fit in some sockets in the same power strip?

This has bothered me for many years, but I'm only now coming around to ask about it. I don't know if this is unique to Sweden or something, but for whatever reason, when I try to plug things into the ...
G. Flurer's user avatar
1 vote
3 answers
121 views

How can nuclear reactors control the exponential cascade of neutrons fast enough to prevent an explosion?

The Wiki article on nuclear reactor physics states that the average neutron lifetime in a typical core is on the order of a millisecond, the exponential factor is as small as 0.01, in one second the ...
2080's user avatar
  • 111
0 votes
0 answers
54 views

Understanding small DC motor curves (torque, efficiency etc)

I have a small DC motor/gearbox unit and the spec sheets is shown below. All* the units are measured at the gear box output, so 100 RPM would be 3,000 at the motor. I'm using it as a generator so am ...
KevInSol's user avatar
  • 117
0 votes
0 answers
44 views

MOSFET pass short spike during power up

I discovered one feature. I've designed circuit for pulse generation and I discovered that it always pass one spike during power up. The circuit is consist of two sections. PMOS for Enable and PMOS ...
Mik9ee 's user avatar
0 votes
0 answers
192 views

Can I use a PWM motor regulator to control a LED string?

I recently bought some LED Christmas lights, but they are too bright. So I was thinking that maybe I could regulate the output by using a PWM regulator? My LED lights have an output of 30V from the ...
Pedery's user avatar
  • 101
0 votes
2 answers
73 views

What do the different "mA" versions of this "battery eliminator" mean?

Page in Swedish, but has a photo: https://www.jula.se/catalog/hem-och-hushall/hemelektronik/batteriladdning/batterieliminatorer/batterieliminator-409049/ This device allows you to select between 3-12 ...
Lowis's user avatar
  • 11
1 vote
0 answers
39 views

Household 3 phase devices

So, I'm not sure if this is the right place to ask this, but have been working on modifying a lawn mower robot that has, for roughly 3 years now been stored under less than favorable conditions. As a ...
Mat NX's user avatar
  • 265
0 votes
1 answer
29 views

Everyday examples of hydraulic pressure drop generating heat

I'm interested in hands-on examples of voltage drop in electronics dissipating the energy as heat, and, thought that the hydraulics analogy, that is the same thing, might be a good way to intuitively ...
User's user avatar
  • 1
0 votes
1 answer
55 views

Power systems unclear voltages

I was looking at this problem: "A balanced delta connected impedance load with (12+j9)Ω per phase is supplied by a balanced three-phase 60 Hz, 208-V source " I do not wish to ask for help at ...
RMS's user avatar
  • 275
0 votes
1 answer
950 views

Line to neutral voltage in three-phase power systems

I have the book "Power system analysis and design" by Sarma. In his intro to balanced LN voltages, in chapter 2 p62 he states: $$V_{LL} = \sqrt{3} V_{LN} \angle30º$$ but later in the chapter,...
RMS's user avatar
  • 275
0 votes
1 answer
60 views

Required Motor Torque [duplicate]

I am interested in constructing an robot which will be responsible for supporting a 200 pound load. There will be four wheels and the diameter of the wheels are 8 inches. The robot will be required to ...
user15588486's user avatar
-1 votes
1 answer
74 views

Battery size and maximal power output [closed]

Generally how does the size of the battery affect its maximal power output(together with other factors like materials, for instance)? Under the current engineering technology and with any possible ...
user271828's user avatar
-1 votes
1 answer
84 views

What is the maximum distance for eavesdropping? [closed]

There is a closed question https://physics.stackexchange.com/questions/276667/what-is-the-maximum-distance-for-eavesdropping-sound-waves on Physics Stack Exchange and I thought this might fit better ...
user271828's user avatar
1 vote
0 answers
97 views

Devices powered and charged via electricity generated by human body

I came across articles like: https://www.sciencedaily.com/releases/2021/02/210210142049.htm https://pubmed.ncbi.nlm.nih.gov/27836601 and https://www.dailymail.co.uk/sciencetech/article-2004801/Weve-...
user271828's user avatar
0 votes
1 answer
70 views

Motor Power for vertical lift in linear slide mechanism

I want to pull up and down 10 kg metal cylinder at 7 inch vertically by using linear slide mechanism in 1 second. What should be the motor rpm, gear type, torque, watt etc? Otherwise how to calculate ...
XO56's user avatar
  • 101
0 votes
3 answers
544 views

How to convert car power into energy (MJ) used per km?

I am currently attempting to do an energy audit regarding how much energy my car uses per kilometer. I am not sure whether my approach to this is right, and it feels like I have made too many ...
Billy Bob's user avatar
1 vote
5 answers
839 views

How can I add the torque of multiple gears?

If I have 3 gears meshed with a gear in the center of the 3 gears as shown in the picture. all of those 3 gears are connected to different power sources. They are free to rotate in the same direction ...
Abdulsalam_Musaad's user avatar
0 votes
0 answers
35 views

Are there any methods to figure out how aerodynamic a race car is without a Cd number?

For the top speed of a car, I believe it's usually limited by drag and horsepower. However, I've also learned that gearing can affect the top speed and acceleration of a car. Are there any methods to ...
user34971's user avatar
1 vote
3 answers
2k views

Does more downforce affect the acceleration and top speed?

How can downforce make a race car faster, apart from being faster around corners? I just recently learned that downforce can help a car accelerate from 0-60 mph faster. Usually, I thought drag didn't ...
user avatar
1 vote
3 answers
990 views

Do gears affect top speed?

Do more gears affect the top speed/acceleration of the car in any way? I know the gears won't increase hp since more gears would increase RPM but would decrease torque.
Race Car Guy's user avatar
5 votes
1 answer
2k views

Alcohol as a working fluid?

Alcohols with their lower boiling point and overall non-toxicity, could they be used as a turbine working fluid instead of steam water?
LazyReader's user avatar