# Questions tagged [mutual-inductance]

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1 vote
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### Toroidal coil as current sensor

Is there a simple way to estimate the amount of flux that is caught by a toroid coil (filled by some core material, like powder iron for example), which surrounds a straight wire with a current ...
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1k views

### Coaxial Cable with signal applied to shield and center conductor grounded

The standard way to drive a signal through a coaxial cable is to have the shield grounded, and a single-ended signal applied to the center conductor. (Throughout, I will assume that $R_{term}$ and \...
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1 vote
155 views

### magnetically coupled inductor equations

How come the mutual inductance for the v1(t) equation has a negative sign and the mutual inductance for the v2(t) equation have a positive sign? I don't properly understand how the signs of the self ...
225 views

### Non-ideal transformer transient state

So, I've encountered a problem that doesn't look that hard, but I simply can't solve it. I have a simple non-ideal transformer circuit and I want to compute V_0. What I was able to find so far are the ...
527 views

### Mutual inductance dot convention

I have a question regarding the dot convention, or more-so want to find out where I am getting it wrong. I start by defining the currents I1, I2, and I3. I1 goes through R1 and L1, while I2 is the ...
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1 vote
482 views

### Mutual inductive coupling in a nodal admittance matrix

I have this question that has been haunting for quite a while now. To compute the nodal admittance matrix $Y_N$ of an electrical network, one can make use of the incidence matrix and the branch (or ...
• 459
290 views

### Why are inverter bus bars made overlapping?

A lot of literature on bus bar design suggests that bus bars should be made to overlap or have equal area such as this. The reason they mention is the total stray inductance falls due to increase in ...
3k views

### What precisely is the numerical (or any) meaning of mutual inductance and, is it useful, representative (of something) or important?

When we consider two inductors that are magnetically coupled, we sometimes talk about mutual inductance. As an example, consider two inductors (such as 9 μH and 4 μH) that are 100% coupled and produce ...
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### How will a PWM controlled relay affect a 800VA transformer on the primary side compared to the secondary side?

Application: A machine that seals boxes with plastic wrapping. The box is sealed by applying a heating element to the plastic for a few seconds. I have a 800VA (220VAC to 54VAC) transformer connected ...
1 vote
2k views

### Mutual Inductance Practical Explanation

I can't understand why the Mutual Inductance is measured in Henry. The self inductance of a coil is the abillity that has a coil to create a magnetic field that produses a voltage on itself so to ...
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### The function 'ddt' in LTspice frequency simulation

I have previously used the time derivative defined by LTspice in a time domain simulation, and I was wondering if this function could be used in frequency domain. If yes, what does it do exactly? I ...
• 459
1 vote
312 views

### Taking into account the mutual inductive coupling analytically in LTSPICE

I am trying to take into account the mutual inductive coupling between three turns in LTspice differently. Instead of defining the inductive coupling coefficient K, I am using the analytical ...
• 459
1 vote
498 views

### Can someone explain the dependence of coupling coefficient to inductance value to me? It seems counter intuitive

According to the formula $K=M/\sqrt{L_1 L_2}$, it seems that k is inversely proportional to the inductance values of the two coils. However, it seems to me that a coupling between two 2uH inductor ...
1 vote
262 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 ...
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995 views

### Common-mode choke on LTSpice

Can someone suggest to me how to select a three-phase common-mode choke with self and mutual inductance in LTSpice?
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### Confusion in modelling of total loop inductance of a rectangular loop

I was reading an article about partial and total loop inductances from this site and in a section where for calculation of total inductance of a rectangular loop is given as: In each portion of the ...
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209 views

### Regarding Magnetic coupled circuit

Here, all the initial conditions are : i1(0-)=0A and i2(0-)=0A When t≥0, the current i1(t) and i2(t) starts flowing. From my assumption, steady state value of i1(t) is 10A but what happens to i2(t)? ...
1 vote
125 views

### Magnetic coupled circuit

I am solving this circuit and according to the dot convension,the j6 ohm and j8 ohm have opposite polarities. Applying kvl to both loops, I got, 10 = j5I1 - j3I2 + j3I2 Or, I1 = -j2 A But I am stuck ...
66 views

### Electrical conductivity circuit help, with two solenoids

I have a project im working on but cant seem to figure out the basic of the circuit. The principal of the circuit is two solenoids wrapped around a chemistry glass making a magnetic field. The purpose ...
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146 views

### Why does LTSpice take so long to solve this circuit?

Using a technique to model transformers for a wide frequency range, I got at a circuit like this one: https://1drv.ms/u/s!AhR86nrv-ZA7ivoz9BZIoXfs4GwXIQ?e=L6mcKd LTSpice takes a long time to solve ...
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156 views

### Calculating inductance using PEEC Model

I'm learning of how inductance is modeled in wires by breaking them down into smaller filaments. I don't understand how the different inductances add up. Say we want to calculate the total inductance ...
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### Why Doesn't the Current in a Transformer Diverge?

I just started learning about mutual inductance and transformers, and I haven't been able to find the answer to this question. I suspect it's really basic, and that I'm just missing some understanding....
1 vote
352 views

### Understanding of coupling coefficient and power transfer efficiency

I am a bit confused about my derivation to get power efficiency from the coupling coefficient. The coupling coefficient $k=M/\sqrt{L_1L_2}$.  V_2=M\frac{dI_1}{dt}=L_2\frac{dI_2}{dt}\\ V_1=M\frac{...
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1 vote
398 views

### Analysis of three phase star star connected transformer

What is going on this circuit(below) and what would be current measured by ammeter(zero or non zero)? Description- These two transformers winding are star star connected and a balance sinusoidal ...
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1 vote
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### Loop inside a loop, where is the mutual inductance greatest?

I had a question while working a problem as to where the mutual inductance of a circular loop inside a rectangular loop is greatest. Is it at the center, because the magnetic field of all four wire ...
235 views

### Mutual inductive coupling and proximity effects

I am struggling a bit to differentiate between proximity effect and mutual inductive coupling. Proximity effect: if a conductor is carrying an alternative current the nearby conductors will witness an ...
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### Why did the designer of this flyback circuit choose to set the oscillation frequency as high as possible with the smallest resistor tolerated?

This circuit uses a current mode controller with an oscillation frequency response of: In the circuit, the designer chose to use a 10nF cap, with a 680 ohm timing resistor, which according to the ...
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1 vote
94 views

### Wirless Power Tansfer Circuit

Hello so my university is closed because of covid. I am allowed one day into their labs to build and test my WPT device. My Tx is very large compared to my Rx. I have tested their inductance with a ...
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341 views

### Two questions about an AC electric circuit: Have I interpreted the dots correctly and where does the negative sign come from?

I asked this question over at the Physics Stack Exchange (https://physics.stackexchange.com/q/549814/263454) and I thought that it might stand a better chance of being answered here. So I am looking ...
1k views

### Thevenin equivalent with mutual inductance

I was practicing for the exam I found a problem in the book as follow : I want to find the voltage Vth so here is what I did : When finding the Vth I didn't ignore the dependant voltage source in ...
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### Mutually coupled inductor modelling in cadence

I used two methods to model two mutually coupled coils. Method: 1) Using 'mind' cell from analogLib. It basically lets you define a coupling coefficient k value. Method:2) Using 'Xfmr' cell from ...
2k views

### How to design wireless charging coils so they are resonant?

I am continuing from this question: What can I use to increase efficiency of inductive wireless energy transfer instead of factory manufactured ferrite plates? I am trying to make somewhat efficient ...
248 views

### What can I use to increase efficiency of inductive wireless energy transfer instead of factory manufactured ferrite plates?

The Context I am a hobbyist with no education in electrical engineering. I am working on a DIY project trying to make water resistant rechargeable bicycle lights. I am doing this as a hobby for fun ...
423 views

### Equivalent circuit of identical transformers connected in parallel or series

I'm trying to figure out how to solve the equivalent circuit for two identical transformers connected in series or parallel on the primary and secondary. Mainly I want to know what the equivalent ...
1 vote
734 views

### Transformer's Primary and Secondary Voltages

In general, which is the phase relationship between the primary and secondary voltages of an ideal transformer? Does it depends on the dot convention?
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1 vote
2k views

### Dot convention meaning

I have two questions about dot convention for the ideal transformer. I have understood how to use them in writing the voltage drops on the coils, but I have some doubts: 1) Which is the physical ...
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### Autotransformer vs Inductive Divider

Which is the advantage of using an autotransformer instead of a simple inductive divider?
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### Total phase inductance of three phase reactor

Consider a three phase reactor (inductor) using E-I or E-E laminations with phase winding on each limbs. Now inductance of R phase is given by: Lr=Lrr+Mry+Mrb Lrr: Self inductance of R-phase Mry: ...
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### Mutual inductance

I am confused about derivation of the next formula The question is about Cm term. We have coupled inductors. The voltage across first coil is And I am ok with it. I understand it. I know ...
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### Resultant voltage function through two opposing coils with mutual inductance

So my question is about the type of relationship in a particular circuit. I would like to know if it is linear or something else like a power. The circuit in question is a pair of adjacent, mutually ...
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