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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What kind of transformer is this?

What kind of transformer is this and how is it used? I'm also confused about why there are only 3 wires. I don't see any other pins on it. Although on the opposite side, you use the number 4 on one ...
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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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Wiring up 110/220VAC to 6V center tap transformer

I have a center tap transformer that does 110 or 220VAC stepdown to two 6V rails (with opposing phases). On the 110/220 side there are what appear to be two separate rails, and the wiring diagram is a ...
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What's this on a single line diagram? What's its function?

The unknown part: It seems like a regular transformer, but is it? What's its function? Why is it grounded? The diagram itself:
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Center tap vs. bridge transformer

I'm designing a power supply to deliver 6V DC with a zener diode acting as the regulator. I found out that there are two types of transformers that can be used. They can be center tap or a bridge. In ...
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Can single clamp measure total current from 3 wires?

Single AC clamp can measure current flowing through a single wire in a non-invasive way. There are AVR/Arduino projects use such a clamp to measure house power usage. However, they use 3 clamps for 3 ...
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It is it possible to safely use a 110V variac (variable transformer) at 230V?

I've come across a variable transformer/variac which is designed to be used with 110V input. Our line supply here is 230V. If I was careful not to exceed the VA rating of the transformer (920VA) ...
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2answers
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Wiring a 2.5km football field with 220v

I have a football field to wire up. It measures 900m x 450m. I need to connect multiple light weight devices that use a 100-220vAc adapter that convert the voltage to 24v for the daughter device. ...
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3answers
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Ethernet connector and transformers

I'm working on an Ethernet connection for a PIC18F4620 with the ENC28J60. I found a useful article here, with a schematic: I see I need transformers between the RJ45 connector and the Ethernet chip. ...
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259 views

Switching power supply output goes to zero when load is attached

I built a SMPS, my first one. It is essentially this one: https://www.infineon.com/dgdl/DN-ServerStandby.pdf?fileId=db3a304412b407950112b418a93b266b, which is a Design Note from about 20 years ago, ...
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662 views

Transformer secondary C.T. Label

Can anyone tell me what the “C.T.” Stands for in the Secondary Volts column (see pic) stands for? When I see that my mind thinks “current transformer” but this is not a current transformer in the ...
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783 views

Ferrite transformer at mains frequency

Is it reasonable to use a ferrite transformer from a big SMPS (LCD TV power supply) as a mains transformer, assuming I split the transformer in half and rewound the coils to provide the proper ...
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Transformer Design: How do I set an N1/N2 ratio by means of selecting winding inductances?

I'm trying to simulate a transformer by using a circuit simulation software. In my requirements sheet, three specifications are given for the transformer: Maximum power (\$P_m\$) of the transformer ...
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4answers
679 views

Relation between transformer core material and application frequency

Regarding the following excerpt from a text: The text mentions that at RF air core transformers are adequate, but for 50/60Hz low freq. applications iron core needed to obtain a low reluctance. The ...
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3answers
17k views

Wiring transformer output in series to get twice the voltage possible?

I already have a transformer 2x 6V outputs. I was wondering can I these in series to produce 12V? Similar to how you would wire two 1.5v batteries to produce 3V.
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How does this circuit in an electric mosquito swatter work?

I had an electric mosquito swatter lying around so I decided to open it up and check out how it works. I understood some parts of the circuit however I did not clearly understand how the rest of it ...
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4answers
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When transformer rating is in kVA, why load is mentioned in WATTS?

The transformer rating is given in kVA, but the load connected is always considered in watts. Why? Eventhough, the load active power is represented in watts it has some reactive power, right? Is ...
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Transformer current peaks

So I am designing a power supply, got everything calculated, and decided to simulate it for a second to see if the smoothing caps keep the voltage above the regulator limit at max current draw. What I ...
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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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Manual transformer winding - dots convention

I've already seen this and this. But I can't decide how to correctly wind a SMPS transformer. This is the transformer: I mantain the same turns direction (CCW if you look at transformer from the top)....
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3answers
572 views

Anyone know the purpose of these two inductors around a metallic ring?

So this link on ebay shows a power board that I have taken out from my microwave. What is the purpose of these two wrapped around a metal ring? Also in general what is the purpose of this power board ...
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992 views

How does the length of a transformers core affect its properties?

I often read mentions of a transformer core's "cross-sectional area", of how it affects the transformers VA rating (although I can't find any formulas for that). But I haven't found anything ...
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3k views

Building a dual-rail, regulated DC power supply: 1 diode bridge & center-tapped secondaries, or 2 diode bridges and separate secondaries?

I'm looking to build a dual-rail, regulated, 18VDC power supply based on the 78xx and 79xx regulators. The circuit is inspired by AMB Audio's sigma25 (amb.org/audio/sigma25/) and sigma26 (amb.org/...
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What clear plastic stripping is used to wrap a toroidal power transformer?

I'm partially rewinding a toroidal transformer just for the pure thrill of controlling the output voltage. I'm sure I'll get over it, but for the moment that prospect is pretty exciting for some ...
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Are AC adapters electrically isolated?

Are AC adapters (e.g. laptop chargers) electrically isolated from ground because they have a transformer? I'm asking this because I read that isolated transformers have a 1:1 ratio whereas AC ...
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7k views

How do I apply PWM signal to the primary side of a transformer to get synthesized sine wave at the secondary side?

I'm trying to obtain a sinusoidal signal (\$f_{sin}=50Hz\$) by using a ferrite transformer. I am going to apply a PWM signal at the primary side (\$100kHz\le f_{PWM}\le300kHz\$). I'm going to use one (...
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426 views

How large would be the transformer for converting a lightning into useful electricity?

My dad asked me the oh-so-famous question yesterday: Why can't we harness the electricity from lighting? After explaining to him the impracticalities of this as far as the amount of energy in ...
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About “leakage inductance”

I'm a little confused about the transformer "leakage inductance" for days. Per this text book, it gives a schematic view of fluxes flow in the transformer: It's apparent that the two leakage flux ...
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1answer
6k views

What happens to a transformer if the supply side is shorted?

Suppose I have an industrial plant, where a switchboard is fed through a transformer. The switchboard have only "passive" loads, i.e. they don't contribute with short circuit currents. If ...
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1answer
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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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1answer
1k views

Transfer power effectively from one coil to another through air

I want to build my own wooden alarm clock. I want the surface to be smooth without any connectors anywhere. My idea is to place one coil beneath the alarm clock, and another pickup coil inside. I ...
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1answer
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Is it possible to have a device with metal case and wireless charging?

Recently I encountered the following idea: that a mobile device manufacturer is not interested in including wireless charging in his devices because that prohibits him from using metal cases in the ...
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782 views

Simulate isolation transformer in LTspice

Hi, I am new to simulating transformers with LTspice, and I struggle getting the circuit to function as expected. The source is a three phase TN-S (wye) connected. Then I wanted to add a 1:1 ...
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Current transformer and bridge rectifier — why the diode drop?

I'm building a circuit to measure AC current using a current transformer, which feeds into a microcontroller's ADC for the actual measurement. As the measurement needs to be fairly accurate, the ...
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1answer
200 views

How do European to American outlet change frequency?

So for the transforming of voltage, a transformer could get a european outlet from 240 to 120 volts. How do these switch the frequency though, do they have to convert it into DC and then generate a ...
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How is a transformer working at 10's of MHz designed?

In this answer a switching power supply using a transformer operating at 10's of MHz range to reduce size is mentioned. How would such transformer be designed? Would it still have a plain old design ...
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Does Tesla coil use near field or far field?

According to Wikipedia a Tesla coil transfers energy (via loose coupling) from one oscillating resonant circuit (the primary) to the other (the secondary) over a number of RF cycles. which I don't ...
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1answer
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Dc isolation (transformer?)

I need to isolate the dc input from the dc current inside the circuit (both 9v), in the same way as a 1:1 transformer isolates the AC current inside the circuit from the input AC. I already found out ...
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1answer
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Isolation Transformers (Capacitive Coupling)

In my application I have an issue with ground loops and to solve this I require to have devices isolated from their drivers. The system operates with a 13.56MHz signal and a wide bandwidth is not of ...
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What is going wrong in this circuit which supposedly should step down AC to arduino friendly voltage?

So I'm using this circuit but when adapter output is disconnected and only midpoint terminal of the transformer is connected the Arduino input pin reads some mV. mid point reads perfect 2.5V. What am ...
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1answer
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Transformer and IC heating in Viper22a SMPS design

I have designed an SMPS using viper22a IC. This gives an output of 9.8V and on adding a 10 ohm load resistor, voltage drops to 9.6V, thus giving an output of almost 10 watts. Here is the circuit that ...
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Power line voltage out of phase with ambient 60Hz electrical noise - why?

I just bought my first oscilloscope and have been tinkering with the measurement of different signals just to learn the ropes and familiarize myself with the scope. One of the first things I noticed ...
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Adding Two Balun Transformers to SA612 Mixer Has No Effect on LO Suppression

I'm experimenting with a SE612 mixer to learn the basis of RF. I read that the mixer can either be single-ended or balanced, and a double-balanced mixer has the best performance in terms of LO-RF ...
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1answer
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How to properly select a transformer in terms of thermal rise

I'm trying to reach a decision selecting a small transformer for a task, from an overseas company (which only significant because of the language barrier). I thought the selection would be easy ...
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1answer
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Winding method for barrel wound secondary center-taped EE core

I'm designing a high-frequency transformer, EE type core, with one primary, and a center tapped secondary. As the secondary current is relatively high and the window area is small, I will use copper ...
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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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Can broken ferrite core be glued and used again?

While trying to disassemble some SMPS transformers for rewinding I have managed to break the ferrite core. I broke the 'arms' of the 'E' half. Also, I found broken core transformers in apparently ...
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Half bridge voltage waveform not following PWM

I am making a 12 V battery charger getting power from 220V AC. The topology is half bridge with capacitor voltage divider, as shown in the SG3525 datasheet. While initial testing on vero-board, the ...
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323 views

High Power Supply over a distance

I'm working on a project and have been stopped in my tracks part way through. I am designing a system that will power an RC over a distance. So I have a generator, and around 300 meters of cable to a ...
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Can I detect zero crossing on the transformer's secondary?

In this answer poster uses the rectified secondary's half sines to detect the zero crossings of the mains voltage. Can you do that? I thought there was a phase difference between primary and secondary,...

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