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I purchased some common-mode chokes and the documentation provided states:

Choke pinout

As this pinout does not correspond to other chokes of the same format, I have doubts about the position of the dots (pins 1 and 3).

So I tried to measure the values of the inductors with an L-meter.

enter image description here

With the assembly on the left I obtain a low value: 100 µH. It would therefore be the differential mode.

With the right assembly I obtain a high value: 40 mH. This would therefore be the common mode.

This leads me to think that the dots should be at 1 and 4 and not at 1 and 3 as shown in the schematic. Is my reasoning valid?

ocrdu
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Nikita
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  • The chance for such a blatant error in a datasheet is somewhat higher for a dodgy manufacturer (or datasheet author gemerally). Where is it from? – tobalt Jan 07 '23 at 13:58
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    Dodgy manufacturer? can't find datasheet. But dodgy vendor: AliExpress... – Nikita Jan 08 '23 at 19:20

1 Answers1

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This leads me to think that the dots should be at 1 and 4 and not at 1 and 3 as shown in the schematic. Is my reasoning valid?

Yes, your reasoning is valid.

You can also prove this using a signal generator and an oscilloscope. If the non-dotted pins (2 and 4) are grounded and a sinewave is applied to pin 1, you'd expect pin 3's output voltage to be in phase if the marking is correct.

Andy aka
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  • So if I understand correctly, if the dots are well placed and the non dotted pins are grounded: by injecting a signal on one of the dot, I must find a signal in phase on the other dot? – Nikita Jan 07 '23 at 15:39
  • @Nikita correct. – Andy aka Jan 07 '23 at 16:17