Questions tagged [transformer]
A transformer couples two or more AC signals through a magnetic field. Often used as galvanic isolation and to transform one AC voltage to another.
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Why do we need an isolation transformer to connect an oscilloscope?
My professor always insists that I provide power to an oscilloscope thorough an isolation transformer. What is the necessity of this? What is the risk if I don't connect it?
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How is using a transformer for isolation safer than directly connecting to the power grid?
How is using a 1:1 transformer safer than using the mains straight off? Is it because you can limit the current coming from the transformer whereas straight from the mains its not current limited? I ...
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Why does a delta/wye transformer make 30 degrees phase shift ?
I'v heard that a delta/delta or Wye/Wye transformers do not make any phase shift. In delta/wye or wye/delta transformers, There is a 30 degrees phase shift between the primary and secondary coils. So, ...
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Why do transformers use so many turns?
Transformers have hundreds of turns on both the secondary and primary winding, and as a result use very thin copper wires for each. But, why do they not just use fewer turns on each winding and get ...
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What is the use of transformers with 3 pairs of wires?
I found a device which has a ferrite core and 3 coils on it. It looks like some type of transformer. What would be its use? I found it in a compact fluorescent lamp.
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Dots in a transformer symbol
I came across this schematic:
What do the dots in the transformer indicate?
user17592
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Power LED bed lamp from mains
I'm attempting to build an LED bed lamp that will be powered by 240V mains. The LEDs are these ones which if I use with a 12V supply and have calculated correctly will draw 0.24W each. I plan to use 5 ...
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Transformer, how the primary current is adjusted to be equal to the secondary load (without considering magnetizing current)?
I am happy to always not understand how does a transformer works ... One answer give me 10 questions ... (So I suggest you to not answer to this question, if you do not want to have more questions :D)
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What is the difference between a transformer and a coupled inductor?
Transformers and coupled inductors seem very similar. Is there a difference in construction? Or only in use?
This question asks something similar, but the answers don't address my question:
Coupled ...
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How to calculate air gap in flyback transformer?
I’m designing (or at least trying to design) a flyback converter on LM3478. I chose the EFD20/10/7-3F3 core [1]. Using a PDF from Infineon [2] I calculated that I need a primary winding inductance of ...
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Cellphone charger has no transformer?
I opened up a really tiny mobile phone charger I have, to see how it is designed. The entire "charger" is integrated into a small 2-pin mains plug, 1 x 1.25 x 0.5 inch, that has an USB socket for the ...
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Why is neutral wire connected to ground at the transformer?
I understand the use of ground wire at the home appliances but why is the neutral wire connected to ground at the transformer? Why doesn't the neutral wire go back to the power generation plants.
I ...
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Magnetic field strength and flux density from hysteresis curve
I am trying to measure the magnetic hysteresis curve of a toroidal nanocrystalline ferromagnetic transformer core made of Nanoperm (datasheet linked) using the following circuit. Each of the windings ...
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Transformer for Flyback power supply
I am designing an isolated DC-DC converter with an input of 12V and an output of 5V@12A, at the moment, a flyback seems like the best option. I have read several books regarding the subject and I am ...
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Is there a dual of the transformer?
Capacitors and inductors are duals of each other.
A transformer is made of two inductors, and transfers power through mutual inductance, through the magnetic near-field (right?) Also, you can vary ...
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How to transform 5 V into 12 V?
I would like to transform 5 V 500 mA (from USB power) into 12 V with a few cheap components.
Is this possible with the help of some generic parts (and not with the help of some expensive transformer, ...
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How does a transformer transmit power from the primary to the secondary?
I'm trying to get my head wrapped around transformer operation and in the process regretting the times I snoozed in my Electromagnetics class as a EE student back when I was a lad :)
I'm looking for ...
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What causes old power supplies to start humming?
I have a number of mains-powered devices that have begun humming (I assume at 50Hz, though I haven't measured it). These include clock radios, a speaker system, a lamp (20W halogen with a transformer ...
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Question regarding use of low voltage high current outputs
I see every day high voltage, high current; high voltage, low current. I rarely see low voltage, high current; why?
I know that I can take a high voltage, high current signal, send it through a step-...
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What are the bare minimum parts needed to operate a magnetron?
I recently took apart a microwave, and I managed to get a magnetron out of it, as well as a transformer that appears to be the power source for the magnetron, but looks a little small for the ...
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Isolation transformer and scope when troubleshooting SMPS
I have a simple question, when troubleshooting a SMPS is highly adviced to use an Isolation transformer. But my question is this, if im using a scope to troubleshoot the "hot" side of my SMPS, both ...
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Transformer primary and secondary voltage phase shift
If we apply a voltage at the primary terminals of a transformer then for this we can get a voltage at the secondary. But they have 180 degree phase difference. What is the reason behind this??
I ...
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What is the percent impedance of a typical residential power line transformer?
Power transformers are rated by percent impedance. A 5% transformer, when loaded to full spec secondary current, will show a ~5% deviation from nominal output voltage.
What is the percent impedance ...
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Why Does DC Load Draw Twice As Much AC Current Through Transformer?
I have designed the following circuit, comprised of 4 loads, 1 of 4.2ohms and 3 of 21ohms, drawing a total of 2.4Arms (1.5A, 300mA, 300mA and 300mA respectively) of AC current through the secondary of ...
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What is back EMF?
I am trying to understand what does back EMF mean.
· Back EMF:
The transformer core once voltage is applied one side will have +ve charges and -ve charges on the other side as shown on the first ...
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How do I design a current transformer?
I want to make a Current transformer using toroidal ferrites to measure 220/50-60Hz AC current(40A max). Is it possible? And how can I calculate secondary turns count?
Ferrite properties:
H = 2000, ...
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Connecting center-tapped transformer to earth ground; or, why am I being electrocuted?
Silly question here.
I've wired up a full-wave rectifier using this dual-secondary transformer. If you want to check my wiring, I connected red-to-orange to "create" the center tap (I assume this is ...
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Buffering the input to a passive RC integrator used to measure magnetic flux density
Note: this is part of a larger question which I was asked to separate into subquestions.
Other subquestions: 1 and 2
I'm using the method outlined here to measure the induced magnetic flux density in ...
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Scaling of magnetic field strength and flux density measurements and shape of hysteresis loop
Note: this is part of a larger question which I was asked to separate into subquestions.
Other subquestions: 1 and 2
I'm using the method outlined here to measure the induced magnetic flux density in ...
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Cutoff frequency of passive RC integrator used to measure magnetic flux density
Note: this is part of a larger question which I was asked to separate into subquestions.
Other subquestions: 1 and 2
I am using a passive RC integrator to measure the induced magnetic flux density in ...
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How to correctly use the formula for calculating the air-gap in a pulse transformer?
To achieve a certain value of the magnetizing inductance (Lm), we can adjust the transformer air gap.
Air gap calculation formula:
There is no particular information on this, but I assumed that:
<...
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Toroidal Core Calculation
Few days ago I got sample of toroidal core from my friend. I don't know any technical details of core just know OD-10cm, ID-6cm, height- 5cm and wet about 1.845 kg(M4 grade CRGO). I want to make ...
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How does the secondary coil of a transformer affect the primary coil? How is it in case of Step-up and step-down transformer? Does it obey Lenz's law?
What changes will (of voltage, current, energy, power, etc) happen to the Primary coil, if an AC supply given to the primary coil, but;
Secondary coil circuit is turned OFF (Open),
Secondary coil ...
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How can "purely" electrical circuits emit sound?
Moving membranes or piezoelectric materials obviously produce sound waves, but how can "purely" electrical circuits such as transformers or DCDC choppers (and others) often have an audible noise? Is ...
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Why does the USA use 110V and UK use 230-240V?
Why does the USA use 110V and UK use 230-240V? What are the advantages? Explain me with calculation. Why do they use different frequencies like 50Hz, 60Hz? What is the reason?
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How do I use a transformer as an inductor?
Lp: Self inductance of the primary winding.
Ls: Self inductance of the secondary winding.
Lm: Mutual inductance between the primary and secondary windings.
Assume that I need an iron core inductor ...
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How to determine which wire is which on a transformer?
Let's say I have a transformer with 3 coils. When primary coil is connected to 230V, two secondaries output 12V. Wires are color coded, but I don't know what colors stand for and there is no ...
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How are neon sign transformers built?
I'm aware that neon sign transformers (NSTs?) produce high voltage - up to 15 kV. But I cannot picture what's inside of one. Wikipedia seems to indicate that they may be a form of resonant transformer ...
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Square Wave input into Transformer
Can a square wave generated using an astable NE555 be used as input of a transformer instead of AC? Say, I generate a square wave of 60Hz using NE555 and a 24V at 6A supply and feed it into a ...
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Why are the transformer windings in series with line and load in this circuit?
I came across this switching power supply circuit and I noticed the transformer is connected in a way I had never seen before.
What is the benefit of connecting it like that? And why does the circuit ...
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How to dimension a power supply transformer?
I always hesitate when dimensioning a transformer for a DC power supply, and I guess I sometimes overdimension them. My confusion stems from the difference in transformer and DC voltage.
If I need 10V ...
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How is transition from three-phase distribution without neutral to three-phase consumption with neutral achieved?
A typical distribution grid supplies 6 or 10 kilovolts AC to a substation near the consumers. This is typically done with a three-phase line without neutral - just three wires going in parallel. Then ...
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How does Ethernet magnetics work?
If you refer to Figure 14 of http://www.analog.com/media/en/technical-documentation/application-notes/EE-269.pdf. There are 2 transformers on each data pair. Can someone help explain how they work? ...
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If a step-up transformer increases voltage, then how current can be decreased ? is really the current in output is smaller?
If a step-up transformer increases voltage, then how current can be decreased ?
If a step-up transformer increases voltage, then how current can be decreased ?
(I'm trying to ask that, in case-of ...
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How does a wireless charger work without a magnetic core passing through both "coils"?
Every time I hear the description of a wireless charging system it goes like this: "remember a transformer? It's the same here - one coil is in the base and another is in the device and when you put ...
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Is it okay to connect a European 240V transformer to a US 240V outlet?
I've an old Bosch German made automotive charger transformer with ratings 14V/9V, 220-250V @ 50/60Hz 132VA. Can I use it on the 220 to 240V outlet here in the US which uses a split - phase system as ...
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Why does short distance wireless energy transfer have such low efficiency?
Wikipedia and numerous other sources cite the following statement about Magne Charge high-power inductive charging system:
For example, the Magne Charge system employed high-frequency induction to ...
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How can I calculate the inductance of the primary of a transformer given a specific load on the secondary?
Inductance in the primary of a transformer decreases as the load on the secondary increases. How can I calculate the inductance of the primary coil? What if it was step up or one to one ratio?
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How can we have high voltage and low current (in transformers), if V = I * Impedance?
I have researched a lot on this topic (including this site) and found this link somewhat helpful : How is it possible to have high voltage and low current? ...
But still it seems ...
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Transformer with hysteresis in LTspice
I would like to model a transformer in LTspice with hysteresis and saturation (or just hysteresis would be nice). I have already tried the Chen model which I don't like and tried to model a regular ...
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