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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3answers
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Transformer winding ratio vs actual winding count

Output voltage of transformer depends on ratio of winding count on primary and secondary coils, but is there an impact on transformer performance by actual winding count? Say, i want to have 1:2 ...
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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 to overcome transistor heat in slayer exciter?

I build this circuit and it works but I have two problems. The major problem is that the transistor becomes very hot quickly. I burnt my transistor due to excessive heat. How can I get rid of the very ...
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3answers
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Why isn't a transformer a short circuit?

I'm a newbie with electronic components and I never fully understood why transformers, while essentially being a short-circuit from a wire perspective, don't act like short circuits (i.e. they don't ...
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4answers
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What is a flyback?

Trying to find this answer is so difficult that I can't even tell whether What is the difference between a transformer and a coupled inductor? is asking the same thing. Some reading suggests that a "...
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1answer
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What are your best resources for winding custom transformers?

What are the best resources that you have found for winding custom transformers? prose, videos, forums, etc. I am looking for things more on the practical side rather than resources explaining the ...
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1answer
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What is the function of this choke-like transformer on the PCB side of this RJ45 jack+magnetics connector?

I came across this ethernet jack+magnetics connector the other day and was wondering what the transformer on the PCB side was for. I thought it looked like a choke, but there is a centre tap running ...
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Help! Need advice identifying the leads on this transformer

Hello Guys. I need help identifying which pair of leads can be used for 110V. I tried continuity test with multimeter and got continuity on the following pairs (1&3) and (2&4). Thanks in ...
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Does a current transformer produce a proportional voltage or current?

I bought a current transformer which looks like the one below: Datasheet I wrapped the transformer around my 10A kettle, and measured the values using my multimeter. Measuring AC Voltage, I ...
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Spot welder: High current advantage over high voltage

I've looked several of these "DIY spot welder" videos on Youtube, such as this: https://www.youtube.com/watch?v=hTaGa93lOGU. We have a much larger number of turns on the primary than on the ...
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Practical way to generate 1500V?

Designing the power supply for an radiation detector, need to supply up to 1500V at 2 mA from mains (170 Vdc). I've largely considered a flyback converter, but cannot find a flyback transformer with ...
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Is the link between the earth/chasis terminal and the utility transformer established through a dedicated wire or the soil?

I was following a tutorial on power supply transformers and at the very beginning I have encountered the following illustration: I added the names TG and HG for the LV transformer ground and the ...
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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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780 views

Why put more than one winding on the low voltage side of a transformer? [duplicate]

In a transformer, the ratio of voltages is equal to the ratio of the number of windings on each coil. So in theory, a transformer with 1 and 10 windings should be equal to one with 10 and 100 windings....
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Connection of center tap for Ethernet transformer

I'm trying to connect an RJ-45 jack with integrated magnetics (Belfuse L829-1X1T-91 datasheet) to an Ethernet PHY chip (Micrel KSZ8041TL datasheet). The TX+/-, RX+/-, and the LED pins are all easy ...
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Three-phase transformer vs. three single-phase transformers

Some time ago a power plant here suffered a lightning strike which destroyed a transformer. A replacement was obtained from a decommissioned nuclear plant somewhere but required heroic efforts to move ...
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1answer
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What use is the copper foil between the primary and secondary windings of a transformer?

I took apart a small transformer. It is of shell construction type. Beneath the primary windings, I found a strip of (floating) copper foil wrapped around the secondary windings. Of course there is ...
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what is the name of this yellow tape around high frequency transformer?

[ what is the name of that tape? , what it is the purpose of it?, can I buy it? And if not, what is the alternative?
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Audio transformer: What to do with an unused winding?

For the purpose of impedance matching and floating a single-ended, ground-referenced signal, I am planning to use an audio transformer like this one. Here's the schematic from the data sheet: My ...
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6answers
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Can the wire of a high voltage power line be used as the primary coil of an air cored transformer? [duplicate]

Back in the 90's I heard this story of a guy who in the 70-80's lived remotely near the power lines and that he was very good in electrical engineering and that he had free electricity by using the ...
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3answers
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Why is power supply from electrical utility referenced to earth?

In response to the question Basic Training for working with 120V AC zebonaut had replied that "A regular wall outlet is referenced to earth" and this provides the close loop for the circuit to ...
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708 views

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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Center tap split supply question

Lest's say that I have the following setup: a split supply (using two voltage regulators: a positive and a negative one) connected to a center tapped transformer (12-0-12). The output of the ...
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2answers
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What if you put a capacitor betwen the plates of another capacitor?

Based on: Is there a dual of the transformer? The picture of the capacitor inside another capacitor seems viable to me. If a transformer is two inductors with a common magnetic field, its dual would ...
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847 views

Transformers as Inductors (Weird Results)

If a transformer's primary and secondary are connected in series, then the total inductance of the result, is greater than the summation of each coil separately. That is to say: \$ L_{total} > (...
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1answer
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Typical zero sequence data for 80MVA transformer

I need to model a 80MVA transformer 132/33kV built in 1973. There is very little information on this transformer but I need to populate certain values in the model. Where can I find typical zero ...
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Transformerless power supply

I'm looking for building a power supply circuit that will convert 230VAC to 5VDC in order to power up an Atmega328P. I also want this to be as small as possible. I know a transformer is one option ...
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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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Dots in a transformer symbol

I came across this schematic: What do the dots in the transformer indicate?
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What makes the transformer in a SMPS smaller?

I'm reading up on how SMPS's work and all the videos say that after the high-voltage chopping stage, a smaller transformer can now be used, because of this high frequency. My question is, how does ...
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How does this circuit start up?

I'm trying to understand how CI HT7A6322 starts up. Relevant part of the datasheet says: Control circuit power supply. Also provides a charging current during start up due to a high voltage ...
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4answers
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Help understanding transformer AUX winding

I'm new here and I'm looking for someone to help clarify the AUX winding of a transformer, more specifically in a switched psu. I see schematics where it's being used either as feedback or voltage ...
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6answers
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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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1answer
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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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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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570 views

Building a power supply, want to stay alive

I am building a power supply for a very old laptop. The circuit uses a transformer (220 V primary to 15 V secondary, 33 VA) and that worries me a little. (Please note that I an enthusiast and so far I ...
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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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What is an audio output transformer? Is it the same thing as an impedance matching transformer?

What is meant by an audio output transformer, does it mean that it is designed to operate at audio frequency or to match impedance?
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In a flyback transformer with multiple windings, how are voltages controlled for different current loads?

This is the flyback transformer I will be referring to: Wurth 760871543 There are three output windings as follows, 24 V at 0.30 A, 5 V at 1.15 A, 14 V (unspecified but in mA range aux winding). ...
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Cutting the ground wire in an isolation transformer?

I bought a non-tech isolation transformer (500w), which I planned to cut the earth mains ground from the output, but leave the chassis grounded; however, when I opened it up I found the output outlets ...
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How does a three-phase transformer work with phases sharing a common core?

Google search reveals a lot of pictures of three-phase transformers. Looks like a common setup is to have three pairs of winding and a shared core. The core typically consists of three "bars" in ...
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Confusion about dot convention in an ideal transformer

I am confused about voltage polarity and current direction in transformers , for example the equivalent circuit of the ideal transformer in figure(a) the instantaneous voltage polarity of the ...
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Transformer labeled 120v-60hz-35va-12v - What exactly does it do?

I have a pool light whose bulb physically broke, but I've found a way to open the water-tight bulb enclosure to get at the actual bulb. I'm trying to either hunt down a replacement bulb (rather than ...
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5answers
585 views

Can I series windings of separate transformers to increase the voltage rating of the whole?

I need a 1:1 transformer, 25VA 600VAC. I'm not having much luck finding such a thing. It occurs to me that I could take five smaller 1:1 120VAC transformers (like this), series all the primary ...
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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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Why does a UPS need an isolation transformer?

Why would we need isolation transformers before and/or after for a UPS system? What are we trying to protect, and from what? I have read that it has to do with grounding and neutral but I didn't ...
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884 views

Isolation transformer to reduce speaker pop

I have some computer speakers which suffer from the following problem: when switches flip in certain devices in the house, like the thermostat on a radiator or the refrigerator, the speakers will emit ...
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In the recent Con-Ed transformer “fire”, what exactly produced the color of the huge blue glow over New York City?

Blue is often linked with technology (e.g. "big blue", glowing pools of water with Cherenkov radiation, aliens in general, Nobel prizes for blue LEDs) as well as traditional things like sparks. In a ...
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How practical would it be to field rewind a large power transformer that's suffered damage from a geomagnetic storm?

It is commonly accepted in power distribution circles that large (large substation-sized or larger -- smaller substation-class transformers are much more readily replaceable) distribution transformers ...
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Which Earth should a chassis be connected to: supply, or local?

I have a doubt regarding the earthing of an appliance and its separate isolation transformer. Consider the following simplified schematics; this is my first guess at which earth each chassis should be ...

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