Tagged Questions

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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0answers
23 views

Magnetizing Inductance Vs. Mutual Inductance

1.) In the transformer equivalent circuit model, is the Magnetizing Reactance/Inductance the same as the transformers Mutual Reactance/Inductance? 2.) Does the secondary have a magnetizing reactance? ...
-2
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1answer
33 views

CT and ADC interfacing [on hold]

How to interface a CT (Current Transformer) with an A/D converter ? I have searched but could not find perfect solution, Are some possible solutions: CT + Burden Resistor + Rectifier + filter ...
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0answers
42 views

How to read part number on a transformer? Inside Dell power adapter LA65NS0-00

I have a dell power supply that doesn't work anymore and am trying to salvage the parts: http://www.amazon.com/LA65NS0-00-Dell-Inspiron-notebook-Adapter/dp/B00115AOTA There's a transformer in here, ...
3
votes
2answers
62 views

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, ...
5
votes
4answers
124 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 ...
0
votes
1answer
26 views

Inductance in Transformers inductors

How can I find a transformers inductors value by using the derivative formula? If I want to generate high voltage spikes from a square wave generator of 10V p-p with a source resistance of 50Ω. I want ...
0
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2answers
46 views

Transformer inrush protection

New guy wound up here after running out of talent! Having tackled my first project using a mains transformer (in the UK - 230V), I haven't put any inrush protection into the circuit. The circuit is ...
0
votes
5answers
82 views

How can the infinite reactance of either primary or secondary in an ideal transformer draw current?

Assumption 1: An "ideal" transformer is said to have very large primary, secondary, and mutual reactance.. (self-inductance/mutual-inductance tending toward infinity), has a unity coupling coefficient ...
1
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1answer
43 views

Operation of a Growler to test armature shorts

Can someone explain to me how a Growler for testing electric motor armatures works please? I have obviously read the Wikipedia Growler page but it is still foggy. So the growler unit acts as the ...
0
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0answers
41 views

Safety / protection considerations for non-switching power supply

My quest for understanding the nuances of circuit protection continues. Today, I'm thinking about the power supply for a device I'm working on. It will need voltages which are somewhat hard to get in ...
1
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0answers
39 views

Why does ignition coil have polarity markings?

I know about one reasonable answer to this. The electron emission is easier from a hotter surface, which in a spark plug happens to be the central electrode. So we should connect this electrode to be ...
0
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3answers
111 views

How do I know if a transformer will output A.C. Or DC?

I recently bought a small transformer to transform 230V AC mains to 7.2V DC to power a small IC and relay. I wired it all up, but as far as I can tell, the output is AC rather than the DC I expected. ...
0
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1answer
57 views

Three phase transformer windings

I have a quick question about three phase transformer windings. if I have a transformer that is Yd11 but I connect the generator to the d-side instead(primary side). Does it become Dy11 connected or ...
0
votes
2answers
89 views

7809 Linear Voltage Regulator Outputs in Series

I'm building a linear power supply that converts 120VAC mains voltage into multiple 9VDC, isolated outputs. I'm using this transformer that has the proper primary winding and 8 secondaries that I'll ...
0
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0answers
40 views

Driving multiple IGBTs with gate drive transformer

I am playing with a circuit I've been working on, which consists of a stack of 15 IGBTs connected in series. The end goal was to drive this "device" with a single toroid transformer, where the drive ...
0
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0answers
28 views

Which configuration of transformer must be used to detect two phases from three phase supply of 440 volts

I am having a transformer which when input with two of the phases of supply(440 volts) is providing around 14 volts. But the same transformer, when used with single phase supply of 230 volts,provides ...
0
votes
2answers
63 views

Info on transformers? Where to find?

I'm quite often taking things apart to salvage the parts and use them in my projects. Right now I'm taking apart an old PC-power supply for a switch-mode lab-supply project. The power-supply in ...
0
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2answers
80 views

Design help for my 1A variable power supply

In a 1A Variable Power Supply circuit given below is it possible to use a 2A transformer and 1A bridge diodes.
9
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0answers
689 views

Outlets not grounded? Remedy? [migrated]

For some months, I'm renting an apartment in the Canary Islands. It looks like the plugs are not grounded. For example, when I connect my laptop, a ThinkPad T420si, then I feel an unpleasant sensation ...
0
votes
1answer
75 views

Amplify a 12 MHz sine wave

I need to take a 12MHz AC sine wave, from around 3.3V - 10V @ 10uA, output 50V, @ 1A (or more). I have the signal generator for signal input, but I am not certain what I need for a circuit to step ...
5
votes
2answers
225 views

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 ...
1
vote
2answers
53 views

What's a probable VA rating for this?

I bought a variac at a garage sale a few months ago and I've played with it since then with a 40W incandescent desk light. Now I want to use it for the incandescent house lights in a small theater. ...
2
votes
1answer
62 views

Transformer calculations and physics

I have an electrical engineering academic background, but since graduation, I have worked exclusively in software and my EE skills are admittedly getting very rusty. Something I never fully understood ...
0
votes
1answer
76 views

Series and parallel transformers?

I have two different transformers. The output of the first one is 15 volts and 1500 mA. The output of the second one is 5 volts and 500 mA. If I connected them in series (to get 20 volts) what will ...
0
votes
1answer
67 views

Use of Audio Tranformers in Amplification

I came across this ckt to make a wireless ear phones using Infrared Signals from IR LEDs. I am unable to understand the use of Audio Transformer here to amplify the audio signal, instead OpAmps would ...
0
votes
2answers
43 views

Step up transformer for low frequency AC with DC offset

What is the best way to step-up a low frequency voltage with a DC offset? I have the following signal coming from a function generator: \begin{equation} V_f(t)=8 Sin(2\pi f t+\phi) + 4 ...
1
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0answers
77 views

Is it OK to place ground plane under transformer?

I have a large transformer (50kHz, ferrite E-core) on the PCB. I want to pass power rails under it on the bottom layer. Should I place a large ground plane on the top layer to shield these power rails ...
1
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1answer
69 views

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 ...
0
votes
0answers
31 views

Importance of IEC 61558-2-6 for isolating transformers

I'm baffled by why exactly some isolating transformers from the same line (of products) fail to conform to IEC 61558-2-6 (but still conform to IEC 61558-2-1) and what is the practical relevance of ...
0
votes
2answers
61 views

Limiting mains current

What would be the best way to limit mains (240V @ 50Hz) current? I want at least 1A of current. The output should be AC 240V at any frequency greater than or equal to 50Hz. It should be able to endure ...
0
votes
2answers
35 views

Sum toroidal transformer outputs

I`m planning to buy a toroidal transformer for driving an LED. The LED needs 36 V and around 1 A. I found a toroidal transformer which has a 230V Input and two 18V 0.83 A Outputs. Can I simply sum ...
-2
votes
1answer
50 views

Can anyone explain a problem in transformer with dot convention? [closed]

Can anyone explain a problem in transformer with dots?
0
votes
1answer
76 views

Winding a Toroidal Transformer

I have a toroidal ferrite core which has an outer diameter of 15 cm, inner diameter of 11 cm and height of 4 cm. I want to use it to make a transformer which takes in mains voltage (240V) and outputs ...
0
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2answers
77 views

Toroidal Transformer High Current Output

Can a 28-0-28 amplifier toroidal transformer like this be practically used as a high current supply at low voltages? I plan to put a couple of turns of 4 gauge wire through the centre. I want to use ...
1
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2answers
78 views

Is this Half-Bridge waveform right?

This started with my question here there is no need to read it, I put it here for additional info. I'm trying to drive two MOSFETs in Half-Bridge topology and I finally could get the pulse ...
0
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0answers
50 views

Problem with transformer vector diagram

I can't understand some vector diagrams of transformer. I tried but unable to understand. I took some screenshots from BL Theraja's Electrical Technology. I want to understand the detail vector ...
0
votes
1answer
70 views

How the step down mini transformers operate in too small current in the primary

For electronic circuits I use step down mini transformers. That can transform the residential 230V AC voltage nearly 14V. I know that (IV)primary = (IV)secondary. That means the secondary current ...
-2
votes
1answer
34 views

My Rf reciever circuit on battery ,but not with a rectified xformer output as source

I just made a Rf circuit that turns on and off a relay depending on the transmitter's message The circuit is working fine when i connect it to a 9v battery. But i cant get the circuit to work with ...
0
votes
0answers
65 views

How to power an arduino controlled thermostat

I'm slowly working on my home automation system which is controlled from a central Raspberry Pi. My current project is to control the thermostat / heating from the Pi based on time, temp, occupancy ...
0
votes
1answer
67 views

Why is there heavy oscillation in my capacitor discharge circuit and is there anyway to fix it?

I have the following capacitor discharge circuit: simulate this circuit – Schematic created using CircuitLab When solving for the voltage across the primary and secondary inductors, I ...
0
votes
0answers
47 views

How do I solve for this circuit? (Coupled inductors)

I am trying to solve for the following circuit (mainly getting a function of voltage on capacitor C): However, I tried my best using node voltage method or mesh current method, in time domain and ...
1
vote
1answer
52 views

Getting more information about a transformer

I'm trying to figure out more information about a small transformer on a old board that we are reverse engineering, can someone give me some advices about how can we reverse engineer this transformer? ...
4
votes
3answers
178 views

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 ...
0
votes
1answer
48 views

Fullwave rectifier theory

Why is it that in full wave rectifiers do you divide the secondary coil by half as stated in this book: (Source) What concept am I missing?
0
votes
1answer
119 views

Dual power supply: two secondaries or series regulators?

I am going to create a simple dual voltage power supply for powering logic (5V) and some stepper motors (12V). What would be a better solution: Would it be to use a transformer with two secondaries ...
1
vote
3answers
68 views

Transformer in flyback DC-DC converter

How can a DC supply be given to the transformer primary in a flyback DC to DC converter? In a flyback converter there is a transformer and DC supply is given to it. How?
2
votes
1answer
101 views

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 ...
2
votes
1answer
64 views

Is RF Transformer Impedance Significantly Affected by Wire Size?

I'm building a Softrock Ensemble III HF Receiver. The online instructions are pretty good, but have a few remnants from an earlier version that no longer apply. So, despite the discussion about the ...
0
votes
4answers
144 views

Impedance matching for amplifier output

I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to deliver this to a 12 ohm ...
0
votes
2answers
68 views

How to purchase the right transformer for an electronic device [closed]

I just purchased an IP telephone that comes with no power transformer. I think the manufacturer assumes that buyers will be using power over ethernet. On the back of the phone where the power jack ...