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Since laminated silicon steel is used in low frequency transformers, can't I also use it as an inductor in a low frequency boost converter, at maybe 100Hz, theoretically shouldn't this work as well as high frequency ferrite core boost converters?

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  • \$\begingroup\$ You might be able to create a low frequency boost converter using a laminated steel core. Do you have any idea what the reluctance is of the core, or the maximum ampere-turns before saturation? I assume this is just for hobby purposes, because most efficient boost converters use much higher frequencies so that inductors and capacitors can be smaller. \$\endgroup\$ Feb 8 at 21:42
  • \$\begingroup\$ I have a laminated silicon steel core used in old DVDs, to step down mains, I honestly don't know much about it's reluctance but I hope my description clues you in on the specs you need to give me your opinion on it, or maybe we can just speak in "ideal" terms so I can have a general perception of how and what happens if I were to use said laminated silicon steel core as a low frequency boost core \$\endgroup\$ Feb 8 at 21:52
  • \$\begingroup\$ You can only store a certain amount of energy in an inductor before its core starts to saturate (and waste energy). Then switch off and the inductor transfers that energy to the output circuit (boosting the voltage). Yours will only do that 100x per second while the ferrite one operates 1000x faster. So, while it'll work, it won't work well. Wind a transformer on that core, it'll work better. \$\endgroup\$ Feb 8 at 21:57
  • \$\begingroup\$ A conventional laminated steel core is designed for a transformer, not an inductor, which needs a much lower permeability to operate efficiently. If you don't understand the difference, you're not ready to roll your own boost converter. \$\endgroup\$
    – Neil_UK
    Feb 8 at 22:09
  • \$\begingroup\$ Could you edit your question to add the fact that your laminated steel core is designed to operate at mains frequencies? It is pertinent to the answer. \$\endgroup\$
    – TimWescott
    Feb 8 at 22:25
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No, for at least two reasons. The reasons that I know are:

Eddy Current

You mention that the core is designed to operate at mains frequencies. Inductors that use laminations of steel are subject to a phenomenon called "eddy current"; basically, the thickness of the steel needs to be sized to the intended frequency of operation. If you look at old audio transformers, you'll see that their laminations are thinner than those seen in power transformers.

Core Saturation

A boost converter works by storing energy in its inductor during part of the cycle, and then releasing it into the output during another part of the cycle. A transformer can be designed so that the core doesn't need to store energy -- it just makes sure that energy going into the primary comes out the secondary. Trying to use a transformer for your inductor core will saturate the core ("magnitize it too much").

Inductors for boost converters are either designed with outright air gaps (which, if you do the math, is where most of the energy is stored, not in the iron) that prevent this saturation, or they're designed with low-permittivity materials that are much less prone to saturation. Either way, they're lower inductance for their size than if they used all-steel cores, yet they can store more energy.

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  • \$\begingroup\$ As a practical project, no, this isn't a good idea. The results will be unsatisfactory, except perhaps for a very low current. As a hobby experiment, it might be a useful learning tool. \$\endgroup\$ Feb 8 at 22:38

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