# Questions tagged [power]

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### Clarification on Parameters and Assumptions of the Parabolic Model for Overhead Power Lines

I am working on a mathematical investigation comparing the parabolic and catenary models for overhead power lines. I need to clarify some details about the parabolic model, specifically its parameters ...
17 views

### Useful power of an induction motor driven at a lower speed

I'm somewhat confused in the physical/mechanical train from the motor to the end load. I have a screw/nut arrangement to move a platform up and down (think about an elevator). Induction motor, pulley ...
1 vote
52 views

### 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?
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29 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 ...
153 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 ...
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66 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 ...
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103 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 ...
1 vote
65 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 ...
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176 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 ...
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48 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? ...
76 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 ...
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251 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 ...
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### 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 ...
173 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: ...
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353 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 ...
95 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 ...
1 vote
253 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 ...
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### 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 ...
• 98
52 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 ...
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45 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 ...
1 vote
329 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, ...
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156 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?
26 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? ...
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1 vote
769 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 ...
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51 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 ...
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 ...
55 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 ...
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 ...
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116 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 (...
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261 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 ...
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1 vote
68 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 ...
1 vote
128 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 ...
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83 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 ...
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46 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 ...
224 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 ...
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77 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 ...
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1 vote
40 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 ...
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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 ...
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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 ...
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1k 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,...
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65 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 ...
76 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 ...
89 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 ...
1 vote
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-...
72 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 ...
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699 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 ...
1 vote
953 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 ...
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 ...
1 vote