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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6answers
105 views

Why does electricity have a phase?

Anyone who's seen the j in electrical formulas knows that electricity has a phase component as well as a magnitude. But where does the phase come from? Does it only ...
-1
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1answer
47 views

Typical Laptop DC Jack Voltage [on hold]

I have a laptop AC adapter with a DC output jack. The laptop does not power on nor does it show indication of receiving power (power LEDs do not light up). The AC adapter is rated for output of 19.5 ...
0
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0answers
44 views

Inverter vs Rotating Machine

My question is in how to relate a 3 phase PV inverter to a classical rotating machine. How is the machines power angle realized by the inverter? In power flow studies, real power flows by ...
2
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1answer
55 views

Must this switch be turned on and off periodically?

Imagine that the AC1-2 is 170VAC at 150kHz~. I simply want to turn the MOSFETs on, and let the AC flow through a inductive-capacitive load. 1) If I can turn the MOSFETs on to saturation by ...
1
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1answer
36 views

AC rms value of pulse train vs RMS value

I have a pulse train with Duty Cycle = 1/4, that oscillates from 0V to 3V. I found the RMS value to be $$ RMS = V \sqrt{D} = 3 \times 1/2 = 1.5 V $$ The DC offset, since it's oscillating from 0V ...
1
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1answer
35 views

Bootstrapping a bidirectional MOSFET switch?

is it necessary to use a driver and bootstrap circuit in order to make this configuration work; Or can I just stick 10V in it like shown? This is to make a bidirectional switch, I'm not pulsing ...
0
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0answers
74 views

Regulating Minimum Voltage

Is it possible to construct a circuit that outputs a voltage of 0 below a certain threshold , similar to a Schmitt Trigger, without using op-amps? In my circuit I want to prevent input voltage below ...
0
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0answers
35 views

Switching 150kHz mains for an LC load

I'd like some input on whether or not to use a mechanical relay or some form of SCR setup to change the capacitance in my LC circuit that is currently operating at around 170V, 1A at 150kHz. (Not ...
1
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1answer
46 views

How switch 20A AC between 2 wires

I'm trying to translate a circuit I made from breadboard to PCB and need some help finding out what components I should be looking for. Basically, so far I have a very simple circuit running 12V AC, ...
0
votes
1answer
49 views

How to amplify a small AC (no DC offset) wave with an op-amp powered from a 0-5V rail and a pot-varying gain?

I'm having a brain hiccup and can't figure this out. I've tried using simple summing amplifiers where I add my wave to an offset of 2.5V and then High-pass the offset. However, I need to be able to ...
0
votes
3answers
45 views

Switch current rating AC vs DC

I'm looking for a high current DC switch (able to switch something like 5V@30A) and I've encountered several DPDT that might do what I need, however they are only rated for AC applications (3A@250VAC ...
0
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2answers
47 views

Change AC signal frequency without changing the voltage

I have a non constant -/+1 Volts to -/+7 Volts AC audio signal. I want to design a device that takes this input signal, doubles the frequency, without changing the voltage. So, the output voltage is ...
0
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0answers
43 views

Mechanical Relay Protection (Controlling AC mains devices)

Trying to make a ucontroller controlled relay to switch mains AC devices. It would have a type M plug on one end(to plug in mains socket in the wall) and type M socket on other end(to plug in the AC ...
0
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0answers
33 views

How can I build a comparator for AC?

This simple scheme to compare Vin1 and Vin2 does work for DC current, but how do I build a comparator for AC current? In fact I would like to compare the RMS values. The purpose of the comparator ...
0
votes
0answers
30 views

Isolated AC mains voltage Measure

I need to measure AC voltage and RMS, but I cant find a good reference. I think that I would need a transformer to step down the voltage, then some kind of amplification to center the AC voltage ...
0
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1answer
58 views

AC current terminals

I have a question that has really been eating up my mind since High School on Ac current and voltages, If its really true and i know it is that Ac current terminals keep alternating at a rate of 50 Hz ...
-4
votes
1answer
35 views

irf840 power mosfet [closed]

can irf840 power mosfet pass ac and also is it possible to logically control it? I have the need to control an ac motor with a microcontroller (msp430). so whenever there is a dc signal from the ...
-2
votes
1answer
53 views

120v AC motor on 220v supply? [closed]

What happens when a 120v 15A AC motor is connected to a 220V supply? In case this is a destruction, what should be the power rating of a converter that is to be used?
0
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3answers
58 views

What is the meaning of negative value of alternating waves?

What does the negative values in AC mean? If we have a symmetrical sine wave with positive and negative amplitudes, then what is the physical significance of negative values? If the answer is ...
1
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3answers
95 views

How does a bridge rectifier work exactly?

If this question was posted before, please let me know. I searched for "how does a bridge rectifier work" and did not find an answer. The part that I especially find confusing is when I have the ...
0
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0answers
55 views

Why does load position affect dissipation of MOSFET [duplicate]

I am trying to use two MOSFETS to pass AC through a load but i noticed uneven temperatures between the two switching devices. In the configuration Below the lower FET heats up more than the upper ...
1
vote
0answers
110 views

One MOSFET appears to get hotter than the other

I am trying to figure out some sources of error in this circuit. Firstly, the lower FET (in the schematic) seems to dissipate more power and heat up faster than the top FET. The shcematic above ...
5
votes
2answers
87 views

How do I combine multiple A/C and D/C power sources into one electrical system? [closed]

I'm looking to design an off-grid power system for my house. I'm a complete novice at this point but I'm willing to do a lot of reading to complete the project. There is a lot I still don't yet know ...
2
votes
1answer
52 views

should I use high voltage or high current to burn carbon rods to dust

I want to burn carbon rods in a vacuum chamber to coat samples in carbon and need the carbon rods to be completely evaporated (worn out /eroded) through electrical power. I also need the +ve ...
0
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0answers
32 views

Exercise on a three-phase system where to evaluate the indication of the wattmeter

I have the following three-phase system where I have to evaluate the indication of the wattmeter W. Available data is: V = 380 ...
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2answers
66 views

What is the 'characteristic frequency' of a certain impedance?

I'm not familiar with that term. Could somebody explain it to me? Is it the frequency at which the phase of the AC current running through the impedance goes to zero? Edit: Here is the context in ...
1
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1answer
51 views

Problems amplifying mV potential differences

I am trying to help my daughter with her science fair project of measuring efficiency of different types of household lighting in various heating conditions. Since she doesn't have the electronics ...
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1answer
67 views

Solving the RMS and Average values

Determine the rms and average values of the following current/voltage waveforms. But before getting the form factor, I should know the RMS value and the average value of the waveform. My only ...
0
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0answers
8 views

Application of SIMPLIS POP analysis to converters with AC input

Is there any restrictions on switching frequency of the converter? SIMPLIS help says: Converters with AC inputs will only POP under very specific circumstances. These requirements are: ...
14
votes
6answers
3k views

Why is sine wave preferred over other waveforms?

Why did scientists chose to go with sine wave to represent alternating current and not other waveforms like triangle and square? What advantage does sine offers above other waveforms in representing ...
0
votes
2answers
115 views

Why does the multimeter need to be set to AC voltage to measure the voltage on secondary winding when driven by a square wave on the primary?

I have a transformer being driven by a square wave at about 9 kHz with a 10/11 duty cycle. In order to measure the voltage on the secondary I have to set my meter to AC. Why is it so? The primary ...
0
votes
1answer
33 views

EM Relay Parameter Calculations

Sometime back I made a relay board to control my table lamp using bluetooth. It worked perfect and so now I would like to upgrade to a beefier power relay. The aim is to be able to control any ...
0
votes
1answer
97 views

Can I use a 220v AC rated switch for 220v 120Hz DC?

so I have this setup: Bridge Rectifier has no Capacitors! So it outputs 120Hz DC I had this without the bridge rectifier, but then, since it's AC and you only break one side the current would jump ...
1
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1answer
66 views

1Mhz+ AC resistance measurements

Is a four point probe applicable for resistance/impedance measurements at high frequencies? Is there a more common technique for AC resistance/impedance measurements? Background: I'm coating ...
3
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1answer
119 views

should AC ground (earth) and DC ground be connected? [duplicate]

I have a power supply (AC --> DC) powering an microcontroller and DC electric motors. I also have the same AC powering a speed controller, which feeds to an AC motor. Should I be connecting the ...
1
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1answer
50 views

ESD Anti static mat Grounding and AC volts

I have an rubber ESD anti static mat on my bench that came without the snaps. I installed 2 snaps, one on each side of the mat. I connected the ground wire from the snap on the mat to the ground in ...
0
votes
1answer
46 views

Using a “quick connect” terminal for IEC inlet or just soldering the wires?

I am using the Schaffner FN284-10-06 power inlet for a project. It has "quick connect" terminals, and it seems like the 3M FDI18-250Q connector would fit them. I've never used a connector like this ...
0
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1answer
31 views

Igbt for AC 32A switch

I have been around this forum, and I am not sure I found my answer. I would like to realize a small and cheap AC switch. Relays being too big, I got interested in IGBT. The goal is to turn on and off ...
0
votes
2answers
110 views

Why does the original Nintendo take 9V AC instead of 9V DC?

i have found an old Nintendo NES 9V wall adapter which is in fact not an AC DC adapter because it's an AC AC adapter. It's the first time i see an AC adapter that ouputs alternating current, Why did ...
0
votes
3answers
57 views

How do I bias an AC signal for sampling?

I want to sample a 10Vp-p 50Hz sinusoidal signal. My ADC can only sample between 0V and 5V, so I need to bias the voltage around 2.5V. I only have a positive 5V power supply. To do this, I was ...
0
votes
1answer
102 views

Using two Mosfets for AC

Im having trouble getting my head around using two mosfets to pass AC. I have reduced my schematic to its bare bones to help keep it un-cluttered. The aim of this circuit is to use PWM to dim a bulb ...
1
vote
2answers
167 views

Sensing AC high voltage to microcontroller

I'd like to sense if I have AC 220V 50HZ available, and convert it to some logical level. I made such circuit, will it work? I use C1 as a resistor. Any recommendations what can be improved? ...
0
votes
1answer
51 views

Multimeter reports voltage but no power?

I have an Insteon FilterLinc, which is an electrical line filter. It doesn't work. When I connect a lamp to the "filtered" outlet, I get no power. So I stuck multimeter probes into the filtered outlet ...
1
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2answers
112 views

Extending the backup runtime of a UPS with an external car battery

I'm looking for a simple/inexpensive way to have a longer power backup time. My fist thought was putting 2 cheap UPSes in parallel. But I quickly found it's not that simple. You would need another ...
4
votes
2answers
202 views

If a large AC generator is overloaded, will it lose frequency or voltage?

If a large AC synchronous generator, like one from a hydro dam, were to receive overdemand from the grid, would it start losing frequency or losing voltage? I know they have several safeguards to ...
6
votes
2answers
142 views

Turn a mains light on slowly

I've been looking at creating a simple circuit to slowly turn a halogen daylight bulb on over about 30 minutes as soon as power is supplied to simulate dawn. I've got a 240VAC 42W halogen bulb that ...
1
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0answers
75 views

How can I convert very high, fluctuating, AC voltage to 240VAC at 50Hz?

I'm about to finish a generator-alternator setup which will generate 9-phase AC electricity at (as yet unknown) very high voltage, most likely around 4800V. I'm not sure what the frequency will be, as ...
0
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3answers
120 views

Can voltages be different if watts are the same? Does DC vs. AC change this?

I'm currently building a home in a van, it's my first tango with electrical engineering. I watched a video on voltages and amps and my understanding is basically like so: a battery is like a water ...
11
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8answers
3k views

How can a phone wire have multiple frequencies at once?

How can a phone wire have multiple frequencies? In my Networks Textbook about DSL vs Dial Up it says the following: The residential telephone line carries both data and traditional telephone ...
1
vote
1answer
91 views

Is it possible to connect a UPS in parallel with the mains?

Short version: When a UPS is plugged in to the mains, is it possible to plug the UPS output back to the same mains? Will that work as an emergency power backup for the mains circuit? Longer version: ...