# 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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### Magnetising Inductance / Primary Inductance

I provided a picture below which shows the transformer calculations and LTspice simulation. In the 1'st picture L11 = 100.5 µH. This value is the inductance of primary side of the transformer. In the ...
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### Jacob's Ladder with 2 kV MOT inductance on microcontroller [closed]

A 2 kV transformer wired to steel rods exhibits expected arcing when the arc is manually started by shorting the rods with a length of wire attached to an insulted stick from a distance. Getting the ...
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### Transformer modelling / coupled inductors

I provided a picture which shows the transformer model and related equations. [Transformer Model and Equations] Source: https://www.youtube.com/watch?v=VrIfvNVBSyE I have 2 questions which are as ...
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### Why mutual inductance be less than or equal to geometric mean of self inductances of coils?

I understand when coils are coupled together the leakage of flux into surroundings causes mutual inductance to be less than self ones but why it has to be less than or equal to geometric mean of the ...
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### Accumulate load time and retain through a power cut?

I have a question around closing a relay after a load been active for a specific elapsed time; and the time is always known even through a total power cut; ideally din rail components would be able to ...
380 views

### How do you choose an audio isolation transformer for a microphone?

I found a few SE Q/A's for audio transformer characterization, but they neither address calculating the impedance match, nor consider signal loss for weak audio sources (like those from a microphone). ...
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### How should we calculate L (inductance) value for a transformer

I am trying to design a transformer using LTSpice with the following specifications: Vin = 230 V @ 50 Hz Vout = 12 V @ 50 Hz Power = 10 W The thing I do not understand is how to calculate the ...
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### Transformer-coupled MOSFET gate drive circuits

I provided two pictures below regarding the transformer coupled gate driver circuit. I know that capacitor blocks the dc when its fully charged and allows AC to pass. However, how does the capacitor ...
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1 vote
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### Calculation of transformer inductance value

I am trying to find a way to calculate the primary and secondary inductance of transformer. I learned that it is changing from one topology to another. My topology is Phase-Shifted Full-Bridge ...
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### Three phase rectifier output current

I´m designing a three phase power transformer, and i´m having troubles with the choosing the current value. After the transformer, goes through a three phase bridge rectifier ( full wave and not ...
324 views

### Different wire length on secondary of a transformer, is this detrimental?

So I’m in the neon industry, and the manufacturers of solid state switched mode HV power supplies recommend using the same length of wire for both ends of the secondary, which would require putting ...
705 views

### Why is this transformer placed on rails?

I have recently passed by the following transformer. It seems to be placed on rails and might be able to roll forward and backwars by about 0.5m each. There are no guards at the end of the rails ...
1 vote
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### Reusing a salvaged known yellow transformer from a USB charger and using it in H bridge configuration

I have salvaged a transformer from a defective USB charger (witch was not mine). the print on it refers to an actual USB charger from the same brand. additionally 12 V in big also printed on it. No ...
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1 vote
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### Would the primary current of the transformer be zero in the no load condition?

Source of the figure. Setting $R_{2}$ and $L_{2}$ to zero and assuming the primary circuit is connected to an AC source and the secondary circuit is left unloaded, then the current passing through ...
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### What is inside of a typical RF transformer?

I am tempted to decap this 500 MHz transformer, but guessing the internals are typical and well-known by experts here. I don't understand why many companies don't even spec the two windings' DC ...
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1 vote
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### Does the primary of an ideal transfomer have a zero reactance?

In the attached figure, the new primary of XFMR1 connected in parallel with the inductor L1 models the original primary of an ideal transfomer. My question is, when modeling the infinite inductance in ...
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1 vote
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### Determining transformer equivalent circuit components

I have made a PCB based planar transformer with a turns-ratio of 8:6. I am considering the T-model as shown below: In the T-model, Lp is the primary side leakage inductance, Ls' is the secondary side ...
123 views

### Why is the generator voltage in phase with current?

The figure shows a toy model for power transmission using ideal transfomers. In this model, the phase angle between the voltage across the load and the current is zero. Let's take the load voltage as ...
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1 vote
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### How does a Current Injection clamp work from a physics persepective?

Current injection clamps are normally described as a transformer with a single turn secondary, which is all fine and good, but the construction of a transformer is different from a current clamp. ...
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### AC Stepdown transformer blown troubleshoot

I've had a ring doorbell pro for about 5 years, it's wired directly to the following transformer output 1 & 4 (24v): It's using the original doorbell wiring, which rightly or wrongly, was wired ...
77 views

### Removing DC component from an AC signal [closed]

How do I remove a DC component in an AC signal during phase fault in a power system?
1 vote
55 views

### Isolation transformer triggers the RCD in the lab [closed]

I am an electrical engineer, and I work in a lab environment. For some inverter measurements, we have bought an isolation transformer, but it triggers the RCD (GFCI for North America) in the lab when ...
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1 vote
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### flyback trasformer 325->12 Dc / 2-3A [closed]

I m trying to design my first circuit for switching supply power 220AC to 12Vdc. My pcb has a voltage 12dc for elettromechanic components and 3.3dc per logic with microprocessor I Connect the 220V AC ...
1 vote
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### What is the mistake in the Current ripple ratio equation?

I was trying to do some research and see some online tutorials to learn designing flyback converter, I have seen this part of that play list , I could deduce some formulas from the video but I had ...
55 views

### Why Does Current Flow Through the Neutral in a Wye Transformer Secondary?

I'm trying to understand the behavior of current in the neutral wire of a wye (Y) transformer secondary (EU residential wiring). Specifically, I'm curious about the following points: Does the current ...
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https://www.youtube.com/watch?v=G8JgS-STozA&t=537s First, I apologize this video is in a different language, but I'll point out what is relevant. So, in this video. There is a man saying that his ...
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1 vote
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### Ring Video Doorbell / ghost rings with 16 VAC solenoid chimes [closed]

I have: Ring Video Doorbell (x4) solenoid chime operating on 16 VAC The chime is a pre-2000's analog device. Presumably it uses an analog circuit to ring the solenoids in a pattern to make a ...
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1 vote
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### How to determine the correct direction of the transformer winding (photo)

I'm winding a transformer for a DAB converter. Image link (MDPI - A DAB Converter with Common-Point-Connected Winding Transformers Suitable for a Single-Phase 5-Level SST System): https://www.mdpi....
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### How to calculate transformer iron core losses?

For a 3 phase, 60 Hz, 6600/690 V, star/delta transformer Rating is 2500 kVA At full load unity power factor it has an efficiency of 97%. Maximum efficiency occurs at 2/3 of the full load How to ...
110 views

### Why in a inverter DC to AC 12V et 220V when I increase the voltage, the current decrease to keep the same power? [closed]

There is a connection between current and voltage. Amps (A) is voltage (V) divided by resistance (R): A = V/R And yes, the more voltage, and thus the more current it draws in an electric component, ...
1 vote
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### Can an audio isolation transformer between a preamplifier and an amplifier cause the amplifier's fuse to blow? [closed]

I'm building a microphone preamplifier. I was having problems with hum (intermittent ground hum when touching the case) and decided to try adding an audio isolation transformer (600 ohm : 600 ohm) ...
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### Does the center tap of a single phase distribution transformer get bonded to the grid neutral? [duplicate]

Here are the two wiring diagram.
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### Is this how a single phase transformer is connected to multiple houses? [closed]

Single phase transformer serving 3 houses: I am not sure if this correct. Can someone confirm?
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### How I can calculate/estimate how many voltamperes I need for an isolation transformer?

I need to power an ungrounded device with live chassis. According to my Google fu I can protect myself using an isolation transformer: https://www.youtube.com/watch?v=3rvEdHyAd2k. Of course I am not ...
1 vote
70 views

### In the perfectly coupled transformer, there is no voltage induced in the primary due to the loaded secondary?

When the coils of a transformer are perfectly coupled, the equations include only the self induced emf in the primary and the mutually induced emf in the secondary. However, when speaking of loosely ...
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### My isolation transformer has its protective earth connected to the output neutral. How should I rewire it for my home lab for "DUT probing"?

I have a rather sturdy isolation transformer in my home lab and I just realized that the primary side earth is not only connected to the output side earth but also to the output side neutral. I don't ...
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### Transformer with same size symbol meaning

I Know these symbols mean a transformer step up or down: But what does this one represent since it has the same size on both sides? Part above taken from this schematic: And this also has me ...
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### Why are these transformer windings used connecting the switch and the series pass regulator in this circuit?

I am looking into this multi-output forward converter and cannot figure why these highlighted windings are connected to the switching side. There's already an inductor to handle the recovery reset. ...
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### Why does this arc die in the center?

I discharged a capacitor across the primary of an old microwave oven transformer. As expected, the transformer made a huge spark. I am generating the spark by charging a capacitor with a bug zapper to ...
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### LLC Half Bridge, Magnetic components testing and implementing problem

In my power supply design I am tested switching operations of half bridge circuit with open circuit and observed clear 155, -155 square wave I want to test step by step so for next step I want to ...
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### Why does a power inductor make a loud noise when first turned on then decay to a calmer "hum" later?

I'm puzzled by this phenomenon. According to my lacking knowledge, a huge current draw at startup is exclusive to electric motors, where the lack of back EMF at zero speed causes big current draw. So ...
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### Two switch forward converter with transient spikes on gate to source voltage - Part Deux

This post is about a similar problem seen in this similar post This 2 switch forward unit has a 750V input, 72 volt output and was tested at 10 and 15 amps out. This new board doesn't have the ...
49 views

### Troubleshooting my DIY Tesla coil setup

Firstly let me say I'm relatively new to HV, so apologies for any silly mistakes. I made a Slayer Exciter circuit, powerful enough to drive a flyback transformer and make 3mm sparks. The circuit is ...
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### Understanding Current Ratings in Step-Up Transformers

A step up transformer increases voltage while decreasing current because we can't get more energy than what we had in the first place. The thing struggles my mind is how his power has a current rating?...
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1 vote
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### Single transformer unit with identical groups of Dz windings around the same core

Background I’m working with a three phase transformer with a 480v Delta primary and a 240v Zig Zag secondary. However, it actually contains two primaries (combined in parallel) and two secondaries ...
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### Does this transformer look like the secondary winding can be easily unwound to change the output voltage?

Similar to this post: How to bring down the output voltage of a 2 x 25 VAC 6 A transformer? (Around 35 VDC after rectifiers) I want to bring down the voltage of this low profile transformer. Does the ...
327 views

### Will an isolation transformer have a noticeable effect on mains hum? Also critique my DIY transformer idea

(Uber-edit - it has come to my attention that I am an ignoramus. This post is being left in place not to highlight my stupidity in particular, but to serve as a warning for others who think ...
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### Dealing with High Voltage Low Current Transformer Inrush and bypassing a Thermistor

As a learning project, I am designing a power supply section of a guitar amplifier that uses a 120V Primary, 250V 45mA 40VA Secondary Transformer. Without any thermistor in-line on the main supply, I'...
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### Substation supplies with touching MSBs

On this site we have the below setup: We have 3 x main switchboards fed via 3 x separate transformers that are existing, this existing MSB has a connecting earth bar only and no neutral connecting bar ...
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### Calculating Core Loss Coefficient (Kfe) for Ferrite Materials

I'm having trouble calculating the core loss coefficient Kfe for ferrite materials. I'm referencing Chapter 15 of "Fundamentals of Power Electronics" by Robert W. Erickson and Dragan ...
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