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
7
votes
1answer
299 views

Help me modernize this audio circuit

When I was a kid, I built this circuit. You hook up a small capacitor to the test leads or maybe a couple in parallel and the speaker will output a different pitch based on the test capacitance. I ...
7
votes
3answers
2k views

How to properly snub transient spikes from a transformer and prevent switch mode power supply burn out

I've received a failed switch-mode DC-DC step down converter (part# LTC3631 from Linear). This circuit was driven by a 24VAC transformer which is rectified on the circuit: simulate this circuit &...
7
votes
2answers
732 views

SMPS transformer orientation with respect to PCB: what's best for EMC?

I have the option of either using a vertical or horizontal bobbin for a flyback SMPS transformer, and I can't conclusively decide which would be best for minimal radiated interference to be picked up ...
6
votes
4answers
32k views

How do step-up transformers work?

I’m trying to figure out how a step-up transformer works. A step-down transformer is simple and logical enough; you start out with a higher voltage and end with less, the remainder being wasted as ...
6
votes
4answers
2k views

How does residential electricity work?

I'm trying to understand how the electricity works in my house. I live in the US. I know that at the transformer, the primary winding induces a current in the secondary winding. The secondary ...
6
votes
4answers
3k views

Why do Rogowski coils work for measuring current?

Rogowski coils measure current by completing a loop of coils around the conductor seen below. This makes sense, but question 1: This is a current transformer, and transformers couple, so in this ...
6
votes
3answers
2k views

Identification of an AC transformer

I have a broken Philips alarm clock FM/AM radio broken, so I stripped some parts out of it. One of it seems like an AC converter, but I cannot find any reference/datasheet about it. Do you have any ...
6
votes
2answers
3k views

Limiting AC current

I am looking for a way to limit AC current. The application I have is used to remove the heat tint on stainless steel caused by welding (the blue-ish discoloration). Removing the tint is achieved by ...
6
votes
3answers
10k views

Do Step-Down Transformers Increase Total Power Consumption?

Firstly I am not at all experienced in electrical matters so forgive any wrong terminology. Here's the situation: I recently moved out of US to a country that uses 220v. We have a single phase step-...
6
votes
3answers
1k views

Creating a coupled inductor with two discrete inductors

Is it possible to create a coupled inductor (with high coupling coefficient) by just placing two inductors very close to each other on the PCB? (Even as far as placing them on top of each other.)
6
votes
4answers
17k views

Minimum number of turns on a transformer

I am trying to wind my own transformer for a power supply. How many turns do I need on my primary winding? I know that the turn ratio determines the voltage ratio, but how do I determine the actual ...
6
votes
6answers
1k views

How is inductive wireless charging of a moving vehicle on a public road possible in efficient way?

Looks like one of the major problems of wireless energy transfer is efficiency. For example, Magne Charge high power charging system seems to have about 86% efficiency which means that quite a lot of ...
6
votes
2answers
2k views

Power Transformer: 110V and 220V input, with two 15V outputs 180 degrees out of phase

I have never designed a power supply before and have a few questions and would appreciate any help. Firstly, I want to use a transformer that can both take 220V and 110V inputs. Can I use a center ...
6
votes
1answer
4k views

How does Ethernet magnetics work?

If you refer to Figure 14 of http://www.analog.com/media/en/technical-documentation/application-notes/EE-269.pdf. There are 2 transformers on each data pair. Can someone help explain how they work? ...
6
votes
4answers
3k views

Physical properties of transformers

In class, we were given equations for the transformer in terms of number of turns primary/secondary and coupling coefficient K, however effect of distance between coils, presence/absence of core, and ...
6
votes
2answers
1k views

When/where to open and close a transformers output

I came across Beware of Zero-Crossover Switching of Transformers (TE Connectivity App Note) where they discuss about how you shouldn't switch a transformer at the zero crossing because it would have ...
6
votes
5answers
7k views

Transformer at primary winding

If transformer is coil (primary and secondary), then when we connect ac source across primary winding which is a nothing but a coil, so entire coil impedance will come across ac source and it will be ...
6
votes
4answers
11k 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 ...
6
votes
1answer
5k views

Open and Short Circuit tests of Transformers

I have knowledge that a transformer in Open ckt is used to find Copper loss and Short ckt is used to find Iron loss But I don't know how to interpret the result of such tests? Further what do ...
6
votes
3answers
42k views

Transformer primary and secondary voltage phase shift

If we apply a voltage at the primary terminals of a transformer then for this we can get a voltage at the secondary. But they have 180 degree phase difference. What is the reason behind this?? I ...
6
votes
1answer
675 views

What is the terminal labelled “U” in some autotransformers?

I'm trying to wire an autotransformer for usage as a speed controller for a brushless motor fan. The terminals are quite self explanatory: Pe for ground, ...
6
votes
3answers
62k views

Effects of changing the frequency of a transformer

If the frequency of a transformer is decreased by keeping voltage same, then what will be the new KVA rating, magnetizing current and inductance, the induced voltage and loss of the transformer?
6
votes
1answer
28k views

Definition and Explanation of Insertion Loss and Return Loss

I'm trying to understand the physical meaning on Insertion Loss and Return Loss on a transformer, specifically RF transformers. The values are often quoted as figures of merit in datasheets, but I'm ...
6
votes
5answers
18k views

Transformers vs. voltage regulators

I'll start by saying that I'm self-taught in electronics, and tend to ask a lot of questions because I don't know NOT to ask them. This is one of those questions. Consider: I have 120VAC and need ...
6
votes
2answers
2k views

Building a power supply for a Vic 20

I recently acquired an early model Vic 20 computer but don't have a power supply for it and thought I might be able to make one. The Vic 20 is the early model with the two pin AC connector - not the ...
6
votes
1answer
712 views

How do they get good primary-secondary isolation on concentric windings?

I've seen plenty of transformers physically constructed with both (or all, if more than two) windings wound concentrically around the center of an E-core--in fact, that seems to be the most common ...
6
votes
2answers
1k views

Can the transformer from an SMPS be used for step-up?

Problem: Stepping up voltage of a high frequency sine wave = 50 KHz to 100 KHz range. Inside SMPS circuits I find a donut shaped transformer that I think is used to step down the voltage from the ...
6
votes
2answers
1k views

How much surge protection do external power supplies provide?

This weekend a very close lightning strike took out several devices in my house. Among the casualties were: 2 TVs 1 cable modem 1 cable box 1 garage door opener One of the TVs, the cable modem, and ...
6
votes
2answers
3k views

Transformer with hysteresis in LTspice

I would like to model a transformer in LTspice with hysteresis and saturation (or just hysteresis would be nice). I have already tried the Chen model which I don't like and tried to model a regular ...
6
votes
2answers
566 views

When to “wind-your-own” vs “scavenge” a transformer?

I often see answers for one-off designs including the advice, "Just wind a transformer...." Like it's no big deal. Did I miss a class in which they handed out a sheet listing the formulas for core ...
6
votes
4answers
2k views

How can we have high voltage and low current (in transformers), if V = I * Impedance?

I have researched a lot on this topic (including this site) and found this link somewhat helpful : How is it possible to have high voltage and low current? ...     But still it seems ...
6
votes
2answers
4k 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 ...
6
votes
1answer
931 views

Does the place of the primary matter in a transformer?

Does it matter whether I wind the primary or the secondary first? I imagine with the primary inside the secondary you'll have less leakage. Is that right? Other reasons to put the primary or secondary ...
6
votes
1answer
7k views

Simulating real world transformer with LTSpice

I'm studying LTSpice, and I'm playing in transformer simulation. I want to modelize a real world power line transformer in a reasonable way: I mean I don't need an exact simulation of some specific ...
6
votes
2answers
2k views

Drawing current sensing transformers accurately

This is more of a stylistic question than anything else, but it important that the sketch be accurate to convey what is really going on. I'm wondering, how does one draw a current loop that is ...
6
votes
1answer
15k views

How does the efficiency of a transformer change with it's load?

How does the efficiency of a transformer change when the load changes, and why is that so?
6
votes
1answer
397 views

How to safely generate 200V from low voltage supply

Unfortunately, this post requires quite a bit of background if it's going to be useful to anybody (including me). I have been trying to build a relatively high voltage power converter for part of my ...
6
votes
6answers
1k views

Mechanism of transformer secondary current

When a transformer has the secondary open and it's driven by an AC source, the only current that the primary draws is the current needed to produce the flux to magnetize the core (like ferrite) of the ...
6
votes
1answer
2k views

Trifilar Transformer Common-Mode Rejection Circuit (Signal Recovery, Hybrid Combiner, RF)

I'm trying to develop a circuit that allows me to effectively subtract two different sources of RF noise from a single signal at the same time. I am planning to use something called a "trifilar" ...
6
votes
3answers
180 views

Design of a switchable dual voltage power supply

My project would benefit from power supply with two modes selected by a switch. The 'normal' mode is full voltage (±13.5V) at full current (~5A), the 'high' mode is double voltage (±27V) at half ...
6
votes
1answer
225 views

Can somebody please explain to me the principle of a T-T Earthing system?

How are the transformer, consumer's side and the generator earthed in a T-T Earthing system? I seem to understand that the generator and its frame should be earthed separately; The neutral of the ...
5
votes
5answers
3k views

Beginner's second PCB circuit design: AC to DC

I am designing an AC to DC converter and I just want to make sure that I am so far doing the right thing — placement of components and wiring etc. — as I am a beginner. Does this look ...
5
votes
4answers
887 views

What is the name for this Encapsulated SMPS

I found this and I'm a little confused. It appears to be a simple component in to which I can put mains voltage and out of which get 3.3V DC without needing any other components - precisely what I ...
5
votes
4answers
978 views

Why are transformers unregulated?

A transformer has a fixed output ratio. E.g. 10:1, for a 23Vac supply from 230Vac. But it is found that under light load the voltage rises above the nominal (at rated load) - why?
5
votes
4answers
3k views

Can a short circuit in the output of a transformer be dangerous?

Assume that I have a 220 to 12 volts transformer with a nominal output current of 3 A (marked "12 V 3 A"). Now what does happen if I connect the two output wires to each other or to a load with very ...
5
votes
10answers
3k views

Best approach to step down 220VAC to 160VAC?

Hey Electrical Engineers, I'm a newbie to electrical engineering (I am a software developer by trade and am starting to work with Raspberry Pis and want to learn about basic circuit design). My ...
5
votes
3answers
23k views

How can I find out which wires are the primary wires on this transformer?

About the amp: This is from an old solid state audio amplifier with an AM/FM tuner. No digital parts or ICs were inside. It was all point to point. Unfortunately I threw out the amp and didn't write ...
5
votes
5answers
5k views

Small step down transformer fuse, primary or secondary?

For a small 24V 1A transformer where should I place the fuse? Secondary 1A fuse or primary 100mA fuse (or above accounting for inrush current)? Mains is 230V. Also, the smallest fuse available in the ...
5
votes
2answers
1k views

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 ...
5
votes
3answers
19k views

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-...

1 2
3
4 5
49