I'm interested in building a SEPIC converter with an input range of up to 1200 VDC. Digikey lists a large number of inductors, which may be viable for my application. But I'm concerned about the voltage in question, and none of the inductors I've looked at have a voltage rating. Are there any particular concerns for using an off-the-shelf inductor in a switching converter at this voltage? Insulation breakdown? Winding style? Something I haven't thought of?
Answer
The answer is yes. Your list of concerns is good (insulation breakdown, winding approach) and I would add to it the clearance between the terminations/leads of the inductor, including any exposed wire between the winding and the component lead that is soldered to the PCB. This is probably not a huge factor, since the L you choose will be pretty big and the leads will probably be spaced far apart, but depending on the winding style, you might wind up (ha!) with the terminals next to each other which could allow for leakage paths or arcing.
This article from Coilcraft explains some of the reasons why voltages aren't specified for inductors and echoes the concerns you've already raised for a high voltage application.
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