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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170 views

Does a floating load on a transformer have no voltage difference with ground?

I think I know the answer, but I'm unsure. I'm studying for my FE, and in the practice exam is the following question: An ideal transformer connects a 120-V, 60-Hz voltage source to a load. One ...
64 views

How to set up an oscilloscope with a 10000 turns 0.05A transformer and an AC power supply, in order to generate a hysteresis curve of the transformer?

I am a high school student investigating how varying the current output affects the shape of the hysteresis curve of a transformer. To measure the hysteresis curve of the transformer's core, I tried ...
85 views

More than sqrt(2)*AC after the rectifier. Why?

I encountered the following issue: supplying one working PCB with two different transformers (same model), the voltages on the PCB are different (higher!), even though the output voltages of the ...
119 views

can somebody explain this sentence in better words?

what is the meaning of "reproducible Al values over time" and why should we need it to be reproducible over time??? and what is "production spread"?
74 views

Double secondary winding equal to center tap?

I am trying to create a power supply with both positive and negative voltages. Is it possible to use this transformer to create such a supply? : https://my.element14.com/vigortronix/vtx-146-050-215/...
70 views

Difference between open and closed center toroid transformer

I just want to know, what is the difference between open center and closed center toroidal transformer. Open center meaning the toroid has a metal rod in the middle while the open center doesn't have ...
2k views

Does the number of turns in Turns Ratio matter in transformers?

Suppose we have two transformers with same turns ratio, $N_2/N_1$. First transformer $A$ is of $100:10$ and the second transformer $B$ is $1000:100$. Both have same turns ratio so both can ...
47 views

How to read a transformer data sheet?

I have been trying to understand this datasheet but I think I am missing some core knowledge. I just want to know what the inductance of the primary is when the secondary is unloaded (I am using the ...
163 views

If I convert the AC from a transformer to DC using 4 diodes and one capacitor and the same for another transformer and connect those DC out in series?

If I convert the AC from a transformer to DC using 4 diodes and one capacitor and I do it for another transformer and connect those DC out in series, what will happen? Is there any problem? How much ...
43 views

I want to ask some questions Here is my original circuit. There is a diff. pair VCO and a LC tank in Tx side. If the Tx/Rx side does not couple with each other, I evaluate the resonant frequency will ...
79 views

Half-bridge transformer driver capacitors overheat

I'm trying to build a DSP plasma speaker using IR2104 half-bridge to drive a TV transformer. The switching frequency is between 15KHz-100KHz. I chose the topology from an old analog plasma speaker ...
98 views

12VDC from two different 230Vac voltage sources

I want 12VDC from two different AC source such as Main and DG supply. At a time only one source will be present. Right now I am using the circuit as shown below. Is there a way to replace two ...
77 views

How to drive flyback transformer with digital input?

I'm building a DSP PWM plasma speaker and using a push-pull to drive a TV flyback transformer: This circuit is not flyback but it works. However I'd like to properly drive the flyback transformer ...
81 views

LTspice - Inaccurate Center-tapped Full Wave Rectifier Results

this is my first post so I apologize if I do not follow any sort of convention. I have researched how Center-Tapped Full Wave Rectifiers should work and from what I found, when the turns ratio is 1:2, ...
64 views

How to pass a signal over isolator with only one side powered?

I have a system composed of a 230VAC zone isolated from a human contact zone with a 7.5mm 2k5 space. On the human side there is a dry contact switch: I am searching for a less than 1€ solution to ...
53 views

What is the effective value of the current of the voltage generator?

I need help with this task, if anyone had a similar problem it would help me. The task is: A voltage generator is connected to the primary of an ideal transformer, transformation ratio n rms values ​​...
137 views

May I get 220v phase-neutral if all the homes in my state seems to give only 127v phase-neutral voltage on sockets? [closed]

In my state (São Paulo, Brazil), theres delta-star transformers that outputs 4-wires. Three phase and one neutral. I've heard that one of these wires of the triphasic (R,S,T wires) and the neutral ...
266 views

Why are transformers abbreviated XFMR?

The "FMR" is intuitive; short for "former." But how do we get "Trans" from "X"? Is there some reason "X" was used specifically? I can't recall seeing ...
113 views

Why did the transformer heat up when connected to a UPS?

I have an electromagnetic vibratory feeder with 2-phase input, 380 V, 0.35 kW. We noticed that the feeder has stable performance when it is connected to a generator because it has constant frequency ...
243 views

Understanding the characteristics of a LED driver

I would like to understand the characteristics of a LED driver I have at home. Here is a photo of the label: I never studied LED drivers before. This post, this article, and this document helped a ...
58 views

How to connect the windings of a dual-winding transformer in series (dot convention)

I'm trying to build a dual power supply. I can find mains transformers that give me two (presumably unconnected) secondary windings of equal voltage, and if I connect them in series, I should be able ...
26 views

THD measurement in transformer Chan Model

I have this trasformer model and I'm trying to estimate the THD at the ouptut using the .fourier option in LTspice. What I notice is that it has 4% of THD at 100Hz for a sine input of 100mV. It seems ...
133 views

Understanding a failing transformer

From my understanding, a bad transformer may have high internal resistance. This causes a lower output voltage than approx. 120V. Say it has an internal resistance of 1ohm and supplies 10 amps, then ...
48 views

A question comparing DC-DC converter and transformer

Transformer is a passive component where the input power is equal to the output power. This comes from the conservation of energy hence Pin = Pout. Can we say the same thing for a DC-DC converter that ...
126 views

per unit impedance

Where is my mistake? Question: Three single-phase two-winding transformers, each rated 25 MVA, 54.2/5.42 kV, are connected to form a three-phase Y-$\Delta$ bank with a balanced Y-connected resistive ...
80 views

How to limit a 350W electric motor to 200W

Current system: Battery: 36V, Motor: max 350W, DC Motor. There is also a controller to increase/decrease motor speed. Without making any (other) changes in the current system, can I introduce a 36V to ...
51 views

So I'm trying to fix the power supply for my espresso machine. I've determined that the transformer is likely the problem (no continuity across the primary coil). The OEM transformer (encapsulated) (...
54 views

Could a bad transformer be the cause of too low power getting to my doorbell chime?

I have a Nest Hello Doorbell, and it seems to be working. However, when I connect it up to my electronic doorbell chime, I can't seem to access certain features of the chime (it has the ability to ...
69 views

Constructing Coupled Inductors with Particular Coupling Coefficient

I'm curious about the design of RF transformers with purposely designed non-unity coupling coefficient. I can see how this would be done in an IC, but how feasible is it at the discrete component ...
108 views

Transformer heat losses

The (I^2R) heat losses in a transformer are caused by the primary and secondary winding resistances, as the page below lists the transformer losses: But what about the eddy currents don't they ...
157 views

How many volts is needed to power a coil

I recently encountered and was trying to troubleshoot a device that's not working properly. In tracing the functionally of the device, I isolated the issue with a coil that does not activate. ...
75 views

Why does the instrument transformer distort the measured voltage?

I have the following instrument transformer for voltage measurement. The secondary winding is directly connected to the analog inputs at the ADC with $R_l=300\,\Omega$ connected across the secondary ...
42 views

I was trying to make this circuit on Proteus but this error appears

I was trying to make this circuit in Proteus as you can see but "[SPICE] transient GMIN stepping at time=3.12737e-007" error keeps appearing. How do I make this error go away?
736 views

What exactly carries energy in a transformer from primary to secondary? [duplicate]

Suppose we have applied a voltage to a transformer with an open secondary, we will get a certain flux in the core and a certain voltage at the secondary depending upon the turns ratio. Now, suppose we ...
105 views

LVDT Simulation in Spice

I have a two-coil LVDT where the position of the rod relates to a level of vacuum. I excited the LVDT with a 2V ptp AC sine wave and measured the Vrms in (700.6V per Picoscope) and Vrms out to ...
46 views

Inrush Surge Limiter [NTC Thermistor] on Primary or Secondary side of Linear Power Supply

In designing a linear power supply, I understand I need to limit the inrush surge current on cold start, to charge up the large bank of filter capacitors, post-rectifier. However, my original intent ...
43 views

Coupled inductors formula

Suppose we have this circuit: simulate this circuit – Schematic created using CircuitLab According to the dot notation rule the current :The convention is that current entering a transformer at ...
67 views

Is there any good way to limit primary current on a low inductance transformer?

For a while, I used hand wind transformers to make high voltage (250v, then several stages of cockroft walton to 750-1000v) from ~12-24v at around 10khz and max 100ma on the primary side. But of ...
77 views

Burned cable while trying UPS transformer with no load

I have this big transformer taken from an old UPS. I wanted to use it to build a linear high current 12V power supply, so I was testing if it was suitable for the task. Unfortunately it has no ratings,...
35 views

Transformer open circuit test [duplicate]

Why did he pick the HV to be the side where he applied the voltage? Usually open circuit test voltage is applied at the LV side. So, from the question how can I know which side he performed the open ...
143 views

Why is the magnitude of mutual flux in a transformer independent of the current in primary?

Consider a transformer with no load, Given $\phi= \phi_m \sin (\omega t)$ $e_1 = N_1 \dfrac{d \phi}{dt} = N_1\omega \phi_m \cos (\omega t)$ \\$E_1 = e_{1rms} = N_1\omega \phi_m \ \frac{1}{\sqrt{2}}...
43 views

How to bring a transformer's secondary impedance to the primary side with k < 1?

I know that when I have a transformer with a coupling coefficient of 1, I can use the formula Z' = Z × (N₁ / N₂)². How could I calculate this impedance with a ...
44 views

If I get the transformer equivalent circuit of the above circuit did I really get a purely resistive circuit with a resistance of n 2 times RLoad . I am asking because I realized that in the ...
48 views

Understanding Schematic utilizing step-up transformer

I have the following schematic. It's designed to step-up voltage and frequency, in range of ~10kV and 20KHz, from 230Vac-50Hz, but I have problems in understanding it. In schematic the box for ...
48 views

Center tap transformer. Voltages 180 out of phase but what about direction of current in 2 parts?

In the center tap transformer (attached picture), my understanding is that volatges in 2 parts in secondary coil would be 180 out of phase. I want to understand the direction of current in both the ...
20 views

per unit transformer winding impedance

As far as I know per unit system removes the transformation ratio, having only one per unit impedance on both sides of the transformer. However, the question below gave different per unit values for ...
22 views

Y–∆ or ∆–Y transformer phase shifting

For Y–∆ or ∆–Y transformer: +ve sequence, quantities on the primary LEAD secondary by 30 degrees. -ve sequence, quantities on the primary LAG secondary by 30 degrees. My question does this change ...
90 views

Magnetic core and compositions

I have a question about magnetics and particularly about inductance per turn, generally indicated as follows $$A_L = \frac{L}{N²} = \frac{µ_{core}A}{l}$$ where A is the cross section of the core and l ...