What are the effects of eddy currents in an inductor core?

Click For Summary

Discussion Overview

The discussion centers on the effects of eddy currents in an inductor core, specifically whether these currents influence the inductance, impedance, or both. Participants explore the implications of eddy currents on the resonant peak and Q factor of inductors, touching upon theoretical and practical aspects of these phenomena.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire whether eddy currents change inductance, impedance, or both, with a focus on their impact on the resonant peak and Q factor.
  • One participant notes that eddy currents create losses, which could lower the Q factor, thereby affecting the resonant peak.
  • Another participant questions if a change in Q necessarily alters the resonant frequency, suggesting that resistance affects Q but may not influence frequency directly.
  • One viewpoint suggests that eddy currents could affect resonant frequency due to heating of the core, although the extent of this effect is uncertain.
  • A later reply argues that, to first order, eddy currents do not change inductance because they flow in phase with coil current, while the induced emf due to inductance is out of phase, indicating a separation of resistive and inductive effects.
  • This same participant acknowledges that deeper eddy currents could have a small effect on inductance due to phase shifts, but emphasizes that this effect is minimal.

Areas of Agreement / Disagreement

Participants express differing views on the extent to which eddy currents affect inductance and resonant frequency. There is no consensus on whether eddy currents significantly change inductance or if their primary effect is on the Q factor and resonant peak.

Contextual Notes

Participants highlight the complexity of the relationship between eddy currents, resistance, and inductance, noting that assumptions about phase relationships and core properties may influence their conclusions. The discussion remains open regarding the specific quantitative effects of eddy currents.

Landru
Messages
107
Reaction score
1
I've been googling around, and I can't seem to find a straight answer to this:

Do eddy currents generated within an inductor core change the inductance, the impedance, or both?

My reason for asking is to understand whether more or less eddy currents will change the resonant peak of the inductor, the Q factor, or both.
 
Engineering news on Phys.org
Landru said:
Do eddy currents generated within an inductor core change the inductance, the impedance, or both?
My understanding is that the eddy currents create a loss (RI2, where I is the eddy current and R the resistance along the current flow).
 
Eddy currents are unwanted currents within the core. Since they encounter higher resistance in the iron core than they would with ordinary conductors the Q will be lowered. The Q will always affect the resonant peak no matter what the cause of the Q changing.
 
Averagesupernova said:
Eddy currents are unwanted currents within the core. Since they encounter higher resistance in the iron core than they would with ordinary conductors the Q will be lowered. The Q will always affect the resonant peak no matter what the cause of the Q changing.

When you say a change in Q will always effect the resonant peak, are you saying that the frequency itself will change?

My understanding is that resistance effects the Q factor, but that the frequency is independent of resistance:

88e615968cc2ae93fc36fd56fccad3cb.png

So maybe my question is: do eddy currents change the value of L at all?
 
One way eddy currents could affect the resonant frequency is the properties of the core could change enough due to the heating. How much I do not know.
 
To first order, no. This is because eddy cuurents (EC's) at the surface of the core flow in phase with the coil current while the induced emf due to inductance is out of phase. Reistive and induvtive effects are separate. That's why coil impedance is a useful concept--the real part is resistive (EC) while the imaginary part is inductive. The reason I said 'to 1st order" is that EC's deep down are shifted in phase and so could affect inductance--but they are exponentially smaller so the effect is small.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 14 ·
Replies
14
Views
5K
Replies
5
Views
4K
Replies
3
Views
3K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K