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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1answer
83 views

Transformer's capacitance

Our main purpose is create the transfer function of a transformer, and we want that for a resonance frequency higher than 1 MHz for our LLC transformer in an LED project. https://www.omicron-lab.com/...
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1answer
152 views

How do I calculate the maximum load on a center-tapped AC/AC transformer for a bi-polar linear power supply with full wave rectification?

I have a 24 VCT AC to AC step-down transformer, which has three wire leads on the secondary. I'll call the secondary leads X, Y, and C, where C is the center tap. With a DMM, the voltage between X and ...
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1answer
457 views

AC ammeter for battery charger

I am having a bit of confusion regarding the use of AC ammeters in a battery charger circuit. The electronics shop guys told that they have been using it successfully in their chargers. Can this be ...
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2answers
1k views

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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1answer
54 views

Defective Transformer Replacement

I've been working on repairing a TV psu, and discovered that the transformer in it is faulty (reading O.L. on every combination of pins except for diagonal in ohms mode on the DMM) I've been looking ...
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2answers
60 views

CT showing different reading at phase and neutral

simulate this circuit – Schematic created using CircuitLab I have attached a simplified version of my test circuit. When the current transformer is connected to the neutral side like in the ...
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4answers
435 views

Power Supply Transformer with 3rd Wire on Primary

I'm sitting here with a $600 espresso machine with its power transformer not working (no voltage coming out of secondary, with 110V feeding the primary). I've been scouring the internet for a ...
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2answers
102 views

Input impedance into center tapped transformers

For a project, I need to find the input impedance into 2 types of transformers at their center frequencies (peak input impedance). Can anyone help me find the peak input impedance? Both L1s are ...
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1answer
43 views

Phase angle of induced voltage in transformer?

Why does the voltage induced in the secondary coil of a transformer lag 90 degrees from the flux in the core? The secondary voltage is induced when the flux cuts it, but then, why does the induced ...
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2answers
1k views

Measuring power transformer capacity

I have a few small-ish unmarked power transformers. I would like to know what their ratings would be if I had the manufacturer's specifications. So far, I have determined that I can safely connect ...
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1answer
178 views

coils/Inductors in series for power transfer

I have an air core inductor that I want to use for resonant coupling purposes. This inductor has an inductance value of 500nH. Is it ok to connect another inductor with a value of 100uH in series with ...
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3answers
359 views

What amp rating of 24VAC transformer for LM317T?

I want to know what size transformer for LM317 at full 30 VDC. I know it's a 24VAC center-tapped transformer but is a 1A or a 5A transformer best suited for a linear power supply of 1.5-30 VDC? I will ...
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167 views

Induced EMF in electrical machines

I am currently working with machines and when I try to understand their principles in-depth, specifically in machines, I got to know that EMF is induced because of any of the two reasons: 1) Time-...
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4answers
95 views

Why is the primary of the Tesla coil placed at the bottom of the secondary?

The primary winding of the Tesla coil is wound around only the bottom portion of the secondary coil and in Wikipedia, they mention that this configuration illustrates the operation of the secondary as ...
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1answer
80 views

3-phase star transformer connection with no neutral for wind turbine

I built a wind turbine a while back and have been using it to power lights in my house. It gives out 3-phase in star setup with no neutral. Neutral is buried in epoxy resin in the casting. It feeds ...
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1answer
24 views

Does partial distance occurs in distribution transformer?

I've seen that in some substations online transformer inspection is performed through partial discharge detection sensors. As partial discharge depends on voltage so I was wondering if these kind of ...
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2answers
910 views

SMPS Flyback transformer selection

I am trying to design a SMPS for a project (I have to make a custom one for integration purpose). This SMPS have universal input (85-265V AC at 50 or 60 Hz) and an output of ideally 53V (but it can ...
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2answers
69 views

Is there any way to estimate transformer's estimated remaining lifetime without testing the oil (or degree of polymerization)?

The common parameter for transformer health monitoring is testing the oil and sediments (N.B., there might be others I don't know). The insulating strength of oil is decreased due to faults, overload, ...
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105 views

How can I change the rising time of signal pulse transformer?

I have a circuit where MOSFET drives signal pulse transformer, and I want to make variable rising time from (100 to 300 ns). How can I make it?
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3answers
80 views

Flux because of secondary coil in transformer

In a Transformer - Alternating current flows in primary winding Causing alternating magnetic field in Iron core Which causes alternating voltage in secondary coil. But I am confused that what would be ...
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1answer
31 views

How can use grounded primary coil transformer with BGJ/MOSFET

So, I have a pulse signal transformer like this (freq is 1MHz): In the secondary coil I want to get bipolar pulses. How can I make it using BJT or MOSFET switches and wich is better? I know, that ...
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2answers
296 views

Why would a tube radio leave the 6.3V heater tap on the transformer disconnected?

I'm attempting to repair a Clarion C104 tube radio. I started the repair years ago, put it away, and now I'm giving it another attempt. When I started the repair, the transformer (Clarion part no. C80-...
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1answer
42 views

What material of core should I use for signal 1Mhz pulse transformer

I want to make 1Mhz pulse signal transformer, and I don't know what material should I choose. I found some epcos cores like N49 but it is for power transformers. Also I found some material with low ...
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1answer
38 views

Testing of HF transformer designed for phase shift full bridge converter(PSFB)

I have designed an HF transformer for a PSFB converter. Specs: Peak Primary Voltage = 800 V Peak Secondary Voltage = 176 V Turns ratio Np:Ns = 18:4 Primary Irms current = 12.38 A Secondary rms ...
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4answers
203 views

Which components cause low humm and medium to high pitched buzz in this computer monitor? [closed]

I recently bought a ten year old 10-bit color fidelity computer monitor (NEC PA301W) that has brilliant display quality but to my sensitive ears has an audible/annoying low pitched humm noise along ...
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0answers
61 views

Transformer output appears to be high

I am checking the voltage output on the transformer pictured below it is noted in the schematic as a 400v/220v/26V transformer single phase 80VA 50/60HZ. The output measured by a multimeter is ...
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2answers
289 views

How does a flyback work when there is no output load?

From what I understand, when the MOSFET is ON, the output diode (D1) is reverse biased. Then when the MOSFET turns off, the magnetic field of the transformer collapses and provides power through the ...
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2answers
143 views

Convert three-phase to a single-phase

For a local power grid powered by a 20 kW diesel generator, I want to feed a set of single-phase loads. But I have problem with imbalance. I have equally divided consumers between each phases as much ...
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1answer
270 views

What happens to current transducer if the line it is attached to short circuits?

I am using a SCT013-30 current transducer to measure current to an AC line. I hook it up to an ADS1115 16bit Analog Digital Converter. I would like to know what happens to the signal when the AC line ...
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1answer
586 views

Find impedence given per unit value-transformer

I really can't wrap my head around this. Three single phase transformers are connected to create a 3 phase transformer. They all have the same nominal values : voltage conversion : 1.2kV/120 V (...
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1answer
50 views

Transformer Inductance Ratio (datasheet)

I am looking at a current sense transformer, PE-51687NL (Digikey). I must be missing something in understanding the datasheet. Digikey says the inductance is 20mH. I assume that this is the "...
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2answers
39 views

Do circuit reclosers of substations respond to any fault on the low voltage side of distribution transformer?

As I don't have any practical experience in power distribution networks, I'm pretty confused about a few things. Typically a lot of transformers are connected to an 11KV distribution line ( 11KV ...
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4answers
98 views

What is the minimum voltage to shock someone? Is a transformer needed or can I use a battery?

What is the minimum voltage to shock someone (on the arm, leg, or finger, not on the tongue). Could this be achieved with just a battery and without a transformer? Is shocking someone just a matter of ...
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0answers
55 views

Trouble keeping the same form of the wave after using transformer

I was making a circuit in LTspice. It took the output of a solar cell as into the Zener regulator. Then I plugged it back in an op amp astable multivibrator circuit. After a few amplifiers I am able ...
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2answers
367 views

Transformer open secondary

In the circuit provided by the link, would having an open secondary coil (not having it connected to any ground) damage the it? The coil is connected to pulsed 240v ac at 50hz. If it is not arcing, (...
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2answers
35 views

Changing the polarity of the transformer on DUT cause voltage offset on DC measurement with insulating amplifier

DUT (device under test) is powered by 230 VAC and for safety we use additional external 230 VAC - 230 VAC transformer (DUT also has its own transformer for buck converting). We are measuring DC ...
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0answers
57 views

Use 12V to 240V inverter to supply 240V power to a transformer

My gate opener was connect to a 240V power outlet on the wall through a AC 240V to AC 16V transformer. The gate opener has a 12V battery inside. This is specification of the gate opener: Motor: 120 ...
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3answers
3k views

Why do travel transformers have a setting for either 50W or 1600W?

I've noticed this "feature" on a number of travel-oriented voltage converters - they either are meant to be used for small 50W loads, OR for larger loads up to 1600W. But you can't run a ...
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3answers
91 views

Impedance matching transformer for piezo acoustic guitar pickup

I am trying to determine the specifics (windings, wire gauge, core material) for an impedance-matching transformer for a piezo pickup on an acoustic guitar. If I can arrive at a 2 megohm input, 20 ...
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3answers
1k views

Transformer voltage step-up and heat

A step-up transformer turns a lower alternating voltage to a higher one, while stepping down the current. This is due to the conservation of energy (energy to into the first coil must equal to the ...
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1answer
71 views

Current Density: Whether to calculate or use thumb rule in designing the ferrite core transformer

I am referring the book Transformer and Inductor Design Handbook[4E] by Colonel Wm.T.McLyman.In which he has emphasised to calculate the current density, rather than using the thumb rule value of 3-6 ...
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4answers
4k views

Why stepping up voltage during transmission considers \$I^2 R\$ but not \$\frac{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\cdot V\$, increasing \$V\$ ...
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2answers
47 views

Isolation Transformer Lights-Up Tester Screwdriver

I have an isolation transformer (230V/230V @ 1kVA) and out of curiosity I wanted to see if the lamp of a tester screwdriver would light up. My intuition said that since the secondary of the ...
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4answers
136 views

Why AM I getting 30 VAC @ 52 A?

Why am I getting 30 VAC @ 52 A? I have three identical transformers with a secondary, 20/10 VAC (8.8/17.6 A). I connected them is series to get 30 VAC across a heating band with a very low resistance (...
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1answer
70 views

What kind of cable I can use to transfer AC 16V power output?

My gate opener uses a AC 240V to AC 16V transformer. I want to connect the transformer to the power supply on the wall and use an extension cable to transfer the output AC 16V of the transformer to ...
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1answer
734 views

Off-load voltage of wall-warts

I need to regulate an incoming DC supply from a wall-wart down to 5 volts. I'm experienced with designing power supplies with ordinary transformers. In this situation, the maximum voltage I can expect ...
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3answers
501 views

leakage inductance on three winding transformer

I have a toroidal 3 winding transformer. It's a step up, lets say 1:10 ratio, the secondaries are identical. If I measure the leakage inductance, shorting 1 secondary at a time, I get about the same ...
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3answers
119 views

How to determine if transformer has air gap or not

I got a transformer out of a broken electronics circuit. I don't know what the circuit was, however I know the transformer was used in some sort of isolated DC-DC converter, as it was right next to a ...
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1answer
706 views

the volt time constant of a pulse transformer

I am looking for a transformer to use with a RS485 driver, but I don't know on what criteria I am to pay more attention: Insulation Voltage or Volt-time constant. Can someone explain me if the volt-...
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1answer
58 views

Audio transformer power level

I am going to use SP-69. https://catalog.triadmagnetics.com/Asset/SP-69.pdf Its power level is 50mW. I am going to use DRV135 to drive audio transformer(SP-69). Output voltage of the DRV135 is 7Vrms(...

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