Model an Inductor: Flux Through Core & Air Around It

[tim9000]

Hi, I'm just curious why we model the ideal inductor as having the leakage inductance as being in series with the ideal core, rather than in parallel to it? Because it would seem to me that the flux goes in two parallel directions, one through the core, and one through the air around the core. Please observe my illustration of what I mean:

 

[berkeman]

The same current creates both the magnetizing and leakage fluxes. That means you need to model Lk and Lm as series-connected elements.

 

[tim9000]

The same current creates both the magnetizing and leakage fluxes. That means you need to model Lk and Lm as series-connected elements.

Good point!

 

[tech99]

Good point!

Leakage flux seems to apply to the case of a transformer, where part of the primary flux does not link to the secondary. I don't think it applies to an isolated inductor. If a perfect transformer has a resistor across the secondary, the primary looks like a resistor. But in practice, there is still a leakage inductance in series with the primary.

 

[tim9000]

Leakage flux seems to apply to the case of a transformer, where part of the primary flux does not link to the secondary. I don't think it applies to an isolated inductor. If a perfect transformer has a resistor across the secondary, the primary looks like a resistor. But in practice, there is still a leakage inductance in series with the primary.

As you say, it would be of limited use, accurate modeling, but just as useful to lump them together in that case.