Off-the-shelf Inductor

How Vendors Specify the Current Rating of an Off-the-shelf Inductor and How to Select It... 

However, in some rare off-the-shelf inductors, we may even find Isat stated to be less than Idc- But what use is that We can t operate beyond Isat in any case So the only advantage, if any, that can be gleaned from such an inductor is that the temperature rise in a real application will be less than the maximum specified. Automotive applications ... 

Having understood basic concepts like voltseconds, current components, worst-case voltage, and also how to do an initial (quick) selection of an off-the-shelf inductor, we will now try to go inside the magnetic component, so as to learn what happens in terms of the magnetic fields present inside its core. We will then use this information to do a more complete validation of a selected off-the-shelf inductor. Then we will find the remaining (worst-case) stresses of the converter. 

Worked Example (6) — Characterizing an Off-the-shelf Inductor in a Specific Application... 

We now pick a promising off-the-shelf inductor — the PO150 from Pulse Engineering. Its inductance is 137 p,H, which is close to our requirement of 127 p,H, and it is rated for a continuous dc of 0.99 A, which is very close to our requirement of 1 A. Its datasheet is reproduced in Table 2-7. Note that the other conditions mentioned by the vendor do not match our application (but that is not unexpected — what are the chances of an off-the-shelf inductor that precisely matches a given application ). Nevertheless we can perform a full analysis, and thus either validate, or invalidate our choice of component. 

In general, we will find that in most ferrite-based off-the-shelf inductors, the designed core loss is only 5 to 10% of the total inductor loss (copper-plus-core loss). However, if the inductor uses a powdered iron core, this number may rise to about 20 to 30%. 

Unlike made-to-order or off-the-shelf inductors, when designing our own magnetic components, we should not forget that adding an air gap dramatically improves the energy storage capability of a core. Without the air gap, the core could saturate even with very little stored energy. 

Question 14 It is much easier to find off-the-shelf inductors. So why is a transformer-based buck-boost even worth considering ... 

Question 22 What are the key parameters of an off-the-shelf inductor that we need to consider ... 

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