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.

Filter by
Sorted by
Tagged with
4
votes
4answers
689 views

Why don't we have wireless charger in every portable device yet?

Today I found Texas Instruments announced a circuit for wireless charging - Ti BQ51013 Qi receiver controller - all the materials emphasis how tiny, lightweight, portable, efficient and otherwise cool ...
4
votes
3answers
1k views

Which has less energy loss - AC step up/step down transformers or DC to DC step up/down converters?

In the EE field, AC transformers are constantly talked about. However, I don't hear much of DC to DC converter modules, even though DC is widely used today, mostly in smaller electronics. Both of ...
4
votes
2answers
2k views

Voltage Balun 1:1

somewhere I have seen that it is possible to build a Balun by using a transformer in the following way: The explanation I have found is that the fact that the ground is only at the primary coil will ...
4
votes
1answer
1k views

What are these obscure components?

I'm having difficulty identifying these components. I salvaged them from a diy power supply enclosure from a garage sale. Each of the black leads in the image attached to female connectors on the face ...
4
votes
3answers
897 views

What is this component and where can I find more details?

I would say it is some kind of transformer but it has the same wire girth on both primary and secondary windings and the same loops count. It had the following label: ...
4
votes
6answers
4k views

Converting 24VAC to 5VDC - Need transformer demystification

I've got an automatic litterbox that 'needs' to be hacked for better control. As it ships, it comes with a 120VAC to 24VAC (300 mA) wall wart that drives the two motors in it. I'm trying not to change ...
4
votes
2answers
252 views

Transformer Inductance not taken into account?

When modelling an ideal transformer, why do we not consider the inductance of the primary and secondary windings of the transformer. Wouldn't this inductance affect the current pulled from the source? ...
4
votes
2answers
510 views

Transformer overload failure mode

I have a fairly large (several pounds) old wire-wound transformer, which steps down 220V to 110V (or, I suppose any other suitable voltages, but that's the intended use). I don't know the rating of ...
4
votes
2answers
1k views

Why my Toroid Isolation Transformer has 112.3v to soil

I'm looking for a brand of Toroid isolation transformer with electrostatic shielding. There may be one brand which has this. Unless there is just none in the whole world? Is it not possible to put ...
4
votes
4answers
9k views

Why does isolation transformer protect from shock?

Perhaps I can best explain the question with two examples: (1) there is PC powered directly from 230V mains (unprotected by RCD or similar), and there is fault in PC that causes line voltage to ...
4
votes
1answer
563 views

What kind of transformer this is?

What kind of transformer is this? Which side is Primary and which side is secondary?
4
votes
3answers
240 views

Transformer Basics

According to my thinking, the answer should be 400-200+200=400V, but the answer given in my workbook is 0V. Can you please point out my mistake ?
4
votes
2answers
340 views

Will moving transformer to separate case reduce noise in opamp-based circuit?

I'm building a simple phono preamp for my friend. I've designed a transformer based power supply to be on the same board as an opamp, then I hesitated - will I get less mains interference if I move ...
4
votes
2answers
36k views

230V to 12V step down transformer

I'm making a water level indicator using an 89C51 for which I need 5 V input voltage. I used a 230 V to 12 V step down transformer and a regulator to get 5 V. I got the 5 V but then the transformer ...
4
votes
2answers
3k views

Transformer with 3 secondary taps

Can I use more than one of the taps on a transformer like this at the same time? If my total load (Amps) is with in the maximum that it can handle?
4
votes
4answers
3k views

Why is stepping up voltage during transmission considers I^2*R but not V^2/R?

During the transmission, the generated electric power is delivered after stepping up to hundreds of thousands or even more voltages by transformers. In that case since P = I*V, increasing V reduces I ...
4
votes
3answers
1k views

When do I twist the wires going to transformer winding terminals, and why do I do it?

I sometimes see the wires of winding are twisted outside of the transformer (or inductor), as seen in the images below. What is the purpose of this? When should I twist winding wires and when shouldn'...
4
votes
2answers
374 views

op-amp circuit to transform input signal

In this typical op amp circuit, how would I go about calculating the value of each component if I want to simply transform the input voltage range into another voltage range, e.g. when input voltage ...
4
votes
2answers
5k views

Can we remove the neutral wire?

If we have the connection shown below (star connection of the secondary part of a TX), the load per each phase is equivalent (balanced load), then the vector sum of ...
4
votes
4answers
199 views

Question about ideal transformers and inductors

Recently I was studying about alternating currents and transformers and I got confused about some of the concepts. I tried a lot of sources but none of them seemed to address the problem. I ...
4
votes
4answers
620 views

Handling transformer inrush current where load varies greatly and is often switched on and off

WHAT AND WHY: I've finally built a isolated supply with a current limiting bulb for my bench. The transformer is a Triad Magnetics VPT230-4350 torrid, 8.5 amps max on the output, 1:1 ratio (home page, ...
4
votes
2answers
406 views

Can cardboard be used as core of the transformer?

Can cardboard be used as core of the transformer? I read that core of transformer do not conduct current, induction produces current in secondary coil. So can cardboard be the core. How do it ...
4
votes
2answers
1k views

Differential high voltage measurement using a transformer

I have questions about the limitations of using a mains-rated power transformer (e.g. a small 6VAC 1VA PCB mount transformer) as a cheap differential probe, so that waveforms can be safely observed on ...
4
votes
1answer
446 views

What's the deal with this beamed mains transformer design?

Take a look at the image. I always understood that transformers have as little air gaps in them as possible, but you can easily look through this mains transformers that I found in China. Not just for ...
4
votes
4answers
1k views

Noisy Transformer solutions

I have a power transformer from an old solid state guitar amp from the 70s and it is extremely noisy. I isolated the issue in the sense, that I took it from the device, stripped it from its case and ...
4
votes
2answers
533 views

Self-oscillating inverter questions

I'm researching a good (and simple) driver for a HV transformer, and found this very simple and elegant circuit on the web: It uses a feedback winding to turn transistors on in an alternating pattern....
4
votes
2answers
6k views

Is it true that power transformer has maximum efficiency at full load?

Is it true that power transformer has maximum efficiency at full load? In other words, is that possible practically?
4
votes
1answer
2k views

Delta-Wye transformer neutral

This is my first post and I am happy I stumbled across this forum. I am preparing for a job interview and have been given a Delta-wye transformer schematic and have been asked to discuss the phase ...
4
votes
2answers
4k views

How to properly wind a high frequency / high voltage transformer?

Please, is there any practical tip / caveat I should be aware, when winding a high-frequency transformer? I'm used to wind 50/60Hz transformers and they do work ok, but now I'm trying to make a high ...
4
votes
1answer
2k views

SMPS Design Transformer Core Selection

I'm trying to construct an SMPS power supply with 230VAC at 50 Hz input and 5.6V/2.5A output. Here is the schematic: The design was optimized with EE19 core selected and I am expected to optimize the ...
4
votes
1answer
421 views

How can a Live-Neutral transformer fault cause 2000 Ampere to flow?

In this critique of an ELV PSU design, it is suggested that a "Live-Neutral" fault could result in a fault current of thousands of amps. It says: Fire – (d) the plastic had a UL94-HB rating ( ...
4
votes
4answers
1k views

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 ...
4
votes
1answer
361 views

Transformer basics: Why don't they shift phase by about 90°?

I learned that current is induced in a conductor by a changing magnetic field. According to this, it would follow that the secondary voltage (sinusoidal input) of a transformer should peak when the ...
4
votes
2answers
462 views

Can someone help me to find the right transformer for this power supply?

So my current project is building a replica of the ARP Pro Soloist synthesizer from the 70’s. The project is mostly going very smoothly, but I am having some issues with the power supply section of ...
4
votes
3answers
2k views

Pros and cons between SMPS switched-mode power supply and heavy line-frequency transformer [closed]

I just found a huge 18V 1A heavy line-frequency transformer. In comparison, I also have a relatively tiny 32V 3A power adapter from a printer. So I notice the size advantage. but what else? Should I ...
4
votes
2answers
261 views

What physical construction features in a transformer control the dot polarity?

As we know, the dot convention is used on transformer symbols to denote whether the transformer "inverts" the signal passing through it or not. However, I am not clear on what in the physical ...
4
votes
1answer
16k views

Transformers parameters

I'm calculating some load flow analyses so I need the parameters of the transformers. I have been able to find most of them but I have some doubts about their equivalences and relations. What is the ...
4
votes
2answers
9k views

Circuit for opening/closing sprinkler valve solenoid?

If I wanted to create a circuit (that was plugged into a typical 120VAC outlet) that was able to open/close a 24VAC Sprinkler Valve, where would I start? My ultimate goal is to control it with an ...
4
votes
1answer
5k views

Driving 12V halogen lamps (downlights)

12V halogen lamps, do they need any special driving? I have seen on some transformers that they output Half-wave rectification to the 12V halogen lamps. Is this how they should be driven or can ...
4
votes
2answers
118 views

How does this signal chopping circuit work?

There is a project online that was posted a few years ago that I want to explore. Unfortunately the progress was never updated so I will have to design it myself from the information that was given. ...
4
votes
2answers
3k 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, ...
4
votes
2answers
7k views

Reactance / Inductance / Impedance of a 1:1 Transformer

I've searched around and poored through what references I have available, and haven't been able to find an answer to this question. Regarding 1:1 transformers, I found a website where an audio ...
4
votes
1answer
430 views

2 full bridge with 2 secondary winding in series… is it possible?

simulate this circuit – Schematic created using CircuitLab Is this possible? Think of the center tap transformer as a 2 winding connected in series
4
votes
1answer
562 views

how to design a switch which works when an input of 0.10 is applied

i have an alarm clock , it's output voltage to the alarm buzzer is around 0.15 volt , i need to attach an electrical appliance to make it operate on scheduled time , for that i had used this circuit ...
4
votes
3answers
8k views

Is there any difference between “induction” and “resonant” wireless energy transfer?

This article compares two systems for wireless energy transfer - one is by WiTricity and another is Bombardier PRIMOVE. I've read their descriptions thoroughly - to me they both look like resonant ...
4
votes
1answer
237 views

How does this isolation transformer protect user from transients/mains?

I'm looking at a pretty simple overvoltage/transient protection circuit designed to protect users but I don't understand what the transformer is doing. The circuit is designed to protect the output ...
4
votes
2answers
434 views

Where should I look for transformer inductance discrepancy?

I'm experimenting with this smallish (~15VA) toroidal line transformer as a "lab" exercise as I'm learning about transformers. Right now it has its original 115V primary winding only; I "unwound" and ...
4
votes
2answers
1k views

Does transformer humming cause notable waste of energy?

AFAIK transformers hum because alternating magnetic field causes pieces of laminated core to slightly deform and vibrate and that is simply a byprocess of how transformers work. However for the same ...
4
votes
1answer
531 views

Can varnish affect the performance of the air gap in an SMPS transformer?

In the past I have built several switched-mode supplies using off-the-shelf transformers just using the datasheet properties without having to worry too much about their construction, however I am ...
4
votes
2answers
561 views

Crosstalk between secondary transformer windings

I have hand wound a transformer which has a 220v primary winding, two 25v secondaries and a 15v secondary: simulate this circuit – Schematic created using CircuitLab I have centre tapped the ...

1
3 4
5
6 7
49