Questions tagged [ac]

This tag refers to alternating current mains power. It usually applies to voltages with >100V RMS, but can also be used for ex. 24V industrial AC power.

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How to buy high-speed 220 VAC - 5 VAC transformer

I was reading this article https://www.etechnog.com/2018/06/How-mobile-charger-works.html and I was wondering how can I search and buy the specific transformer that AC-DC converters use to step down ...
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5 answers
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How to determine the most efficient voltage transformation?

I have a 12VDC battery bank and an appliance I want to run that requires 26VDC input. The power requirement for operation is approximately 100 watts. I have a 12VDC power adapter (not sure if it is ...
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-4 votes
5 answers
117 views

Doesn't the law of conservation of energy invalidate Ohm's law?

Imagine I have a power supply supplying a 12 amp AC current of 12 volts. The resistance of the circuit, consisting of only a copper wire and a resistor, is 1 ohm. In this instance Ohm's law holds true:...
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3 answers
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Usage of peak-to-peak voltage and RMS voltage

Why are RMS values and peak-to-peak voltages common in use? For example RMS voltages in the context of noise. I see especially for peak-to-peak voltage no practical usage. Why should I need more ...
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Digitally adjusting AC voltage for a motor

Basically I have an extraction fan motor that runs full speed at 230V, at 130V it runs around half the speed. The original chip allows switching between few voltages (and therefore, fan speeds) upon ...
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AC Voltmeters: Transformer or Resistive Network

Do most high resolution AC voltmeters use a transformer on the input, or simply scale down the AC magnitude with a resistive network? Thanks!
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1 answer
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Can I run 460VAC 60Hz 3 phase rated motors on 380V 50Hz mains?

I have an upcoming project that is going to China which will be using 380Vl volt 50Hz. Will motors that I've used before which are rated for 460V 60Hz, be able to operate at 380V 50Hz? I've read ...
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What is the mechanism for charge distribution in an infinitely long conducting wire?

If we supply along conducting wire conductor an AC supply, is the charge distribution inside the wire similar to the image given below? Also, do electrons push each other to generate this charge ...
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Multiple NPN driving single PNP

In my circuit I have multiple NPN collectors tied together driving a single PNP which turns on a ATTINY10 anytime the Optocouplers turn on. The logic I want is: Optocoupler turns on, indicator LED ...
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Why are there two different charges on a patch antenna? How are these charge distributions formed?

If we apply an AC signal to a capacitor, we can see only one type of charge on an individual plate. If we apply an AC signal to a patch antenna, there are two different charge distributions on the ...
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Identify Vintage Power Cord for Sears Electric Tray

I found this vintage Sears electric warming tray but it's missing a power cord. I tried a 2 prong figure 8 cord but the holes were too close together or too small to fit. Here are pictures of the tray,...
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Wiring hard start kit to compressor

First of all, I am not sure if this is something for electrical engineering or home improvement, therefore feel free to flag it as wrong community if you disagree with my choice. Now, I am trying to ...
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What should I do with the neutral line while running 3-Phase induction motor?

As far as I've seen, low voltage distribution lines (3-Phase 440 volts) have four wires - three phases and one neutral (Ignore the earth cable). What should I do with the neutral line if I want to run ...
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Laptop AC adapter power cord [closed]

I suppose this is probably a stupid question, but my laptop was expensive so I want to make sure I'm protecting it well.. I ordered a second AC adapter for my computer, a used OEM one, but the cord ...
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2 votes
2 answers
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Why is my maths saying that increasing turn count will decrease magnetic field strength in an AC coil?

I’m trying to make a device that can propel rings of conductive material upwards and make them hover, like the one seen in this video at 6:24, albeit on a smaller scale. I got a stepdown transformer ...
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Relation between signal mixer and filters

Mixer output shown as red wave: Can a band-pass filter be used to remove the low frequency shown as a blue sine wave and leave the rest high frequency just like the frequency shown as a green sine ...
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How to properly start an induction motor using a variable frequency drive? [closed]

I've seen on several websites that a variable frequency drive (VFD) can be used as a starter for induction motors, but didn't find any details calculation on what should be the starting frequency. In ...
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1500W wirewound resistor tripping house fuse 20A / 120V

I have a TE wirewound resistor (TE Connectivity TE1500B22RJ, TE series solder lug panel mount resistor, 22 ohms +/-5% 1500W), which I am hooking up a 120V outlet rated up to 20A. I am testing a ...
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In a DC power-supply design, is it safe to connect the GND of the secondary side of the transformer to the AC input part?

This is a design that my colleague was using to supply power to some op-amps in an accompanying AC voltage measurement circuit. I'm wondering why the ground of the secondary side of the transformer (<...
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-1 votes
1 answer
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14VAC to 11VAC (~200mA) Using a small transformer

I have an application that requires a transformer with 120VAC 60Hz on the primary and 7VAC/11VAC (200mA) on the secondary. Unfortunately, while this part is available in some countries I have not ...
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8 votes
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Why does a full-wave bridge rectifier have noisy output with no load?

Purely academic question: I have a little bridge rectifier made out of four 1N4001 diodes, being fed by a transformer putting out 12VAC. When I run it without anything else attached to it, the ...
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What kind of motor is needed to make this work?

Not exactly sure what kind of AC or DC motor would be needed to make this. Is it even a realistic idea to make electricity by using a motor as a generator? https://www.youtube.com/watch?v=V3NtSp6aAbs
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3 votes
2 answers
371 views

Electrolytic capacitor and AC

I'm doing an experiment to investigate the relationship between frequency and capacitance. The experimental setup is to connect an aluminum electrolytic capacitor to a function generator and use an ...
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What are the assumptions involved in below rectifier output waveform?

The below waveform shows peak current occurs at the instant when diode starts conduction. Why is the peak current not happening at the max input voltage point? Usually the rectifier output caps are ...
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18 votes
3 answers
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Does this AC to DC + breadboard setup have the ability to kill/severely hurt me?

I'm currently building a PC peripheral that uses an AC to DC converter to power a set of DC fans. I'm not a trained EE or electrician, so I want to make sure I'm not putting myself a risk with this ...
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How to construct a 4 input AC AND logic gate?

simulate this circuit – Schematic created using CircuitLab I have four different safety switches connected to four different devices. If one of those safety switches trip then I want a signal to ...
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3 votes
4 answers
673 views

AC volt meter using an Arduino not giving steady reading

I am trying to make an AC voltage reading system according to the circuit below which I found online. My voltage is coming out cyclical - why is that? Is the capacitor perhaps to blame for not ...
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1 vote
2 answers
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Capacitor in AC

I am new in this sphere and I would be appreciated to have some help. So I have this schema, and I don't understand what is the reason that the value of the capacitor amperage decreases after every ...
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Current calculation of three-phase system with "extra" resistors

I know you usually say that I should solve it a little bit and then ask for help, but in this question unfortunately I don't know where to start. This is a question about a three-phase circuit with ...
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1 vote
0 answers
56 views

Running 230VAC through a PCB

I've currently got a system which runs 230VAC, 24A through a series of 3 groups of 8 terminal blocks (8A each group, 1A per terminal block), through a relay each (8A), and then through 3 terminal ...
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2 votes
0 answers
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Hark There is an Arc

AC mains power is almost always transmitted at 50 or 60 Hz. Accepted reasoning is that lower frequencies make transformers larger and higher frequencies have greater transmission losses. ...
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How to calculate frequency of an AC source with variable frequency using Arduino

I have an AC current source. Its properties are Maximum Vrms=15v Maximum Frequency 125 Hz Minimum Frequency 5 Hz The current source is pickup coil of a motorcycle... Vrms range is approximately 0.7v-...
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LED bulbs increasing measured AC line voltage?

I was troubleshooting an LED light flickering issue on a ceiling fan. Note the house is a partial knob and tube conversion with no grounds, switched neutrals etc. First I measured the voltage at the ...
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0 votes
1 answer
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Apparent power for assymetric configurations

I know that the total apparent power S in a 3 phase load for Wye-Wye or D-D configuration = sqrt(3)Vline*Iline. Is it the same for Wye-D or D-Wye configuration?
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1 vote
1 answer
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Can I use a 50m network cable to power two 24VAC solenoid valves?

I have purchased two 24V AC solenoid valves to control the irrigation in my greenhouse. The plan is to install the two valves inside the greenhouse and power them using relays in the garage which is ...
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1 vote
1 answer
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Portable AC power source earthing?

I have an 12V to 230V inverter in my car but get confused about ground it. The inverter is centre-tapped, means live-earth voltage is +115V, neutral-earth voltage is -115V, this gives an L-N voltage ...
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A couple of questions about transformers

1: I accidentally supplied 9v to a 4.5v - 0 - 4.5v transformer like this: And it was working for a about a second and then it stopped and isnt working. Have i killed it? 2: Can you use a square wave ...
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2 answers
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How to wire multiple LED lights to an AC outlet

I am trying to do an arts and crafts project (from this tutorial: https://www.youtube.com/watch?v=D5LjGFkpApw) But instead of using a battery pack like he is in the video I would like to plug the ...
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How can I set the peak voltage in an AC waveform?

I am trying to make a small generator, nothing fancy just a coil of wire, and I was curious as to how the peak voltage of the waveform could be changed. Is the only way to increase this voltage with a ...
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2 votes
3 answers
160 views

Why does reactive power not output useful work in a motor?

They say that negative power from an inductive circuit means that power is flowing from the inductor back to the source, so no work is done. For a motor, even though the power or current is flowing ...
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2 votes
2 answers
346 views

How to hook up a transformer to 120V AC?

I'm building a DC power supply and am stepping down my voltage from 120V (from the outlet) to 24V through a transformer. I will be soldering the 3 wires that plug into a North American electrical ...
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3 votes
3 answers
747 views

How can failure of Class Y capacitors lead to electric shock?

This article mentions "Due to the fact that equipment cases are usually grounded, Y caps require higher safety to avoid risks of electrical shocks to users" How can an equipment with ...
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1 vote
1 answer
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Relation between line voltage and phase voltage in delta configuration

I have read answers pertaining to this same question, but I could not understanf why the phase voltage is equal to line voltage. This answer says: In a delta system, the two points required to ...
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0 votes
2 answers
89 views

Inductive power capture from AC power cable

How much power could be captured per inch by wrapping a wire around a standard 120V power cable for each amp-hour flowing through it (or whatever reference point makes sense if it's not that)? Assume ...
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AC single-phase fan motor works (almost well) without start capacitor, but not with the correct capacitor connected?

I have a fan motor from a mobile a/c unit here which stopped working. It is for the fan that blows the warm/hot air trough the a/c condenser (exhaust air). 240V AC motor with a 4uF (+/-10%) 450V ...
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2 votes
1 answer
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LTSpice RL circuit simulation with ideal inductor and inductor from database

I am trying to simulate a simple RL circuit as shown below, the top one using inductor from the component library and the bottom one is picked from the database. Below is the properties of L1 ...
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1 vote
1 answer
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Homework: impedance equivalence with transformer

I am working on this homework problem and I am wondering if my approach for finding Zeq is correct. I know my matrix is correct, but I feel like I need to do something else to find the correct ...
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-2 votes
3 answers
97 views

What happens if you connect an AC generator to an AC motor? [closed]

An AC generator (or alternator) converts mechanical energy into electrical energy. An AC motor does the reverse. What would happen if we connect the two in such a way that the output rotational ...
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2 votes
1 answer
53 views

How to safely protect input sensing AC Line Voltage

I'd like to detect the presence of AC line-level voltages in my PCB project, and I'd like to follow best-practice for doing this. I'm a controls engineer so I'm happy with dealing with mains with ...
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0 votes
2 answers
79 views

Can a bipolar capacitor in an AC circuit store even a tiny amount of energy? [closed]

I've been reading (some Q&As on here and other bits on the web) about the behaviour of bipolar capacitors in AC circuits. I understand that a polarised capacitor cannot work and will likely ...
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