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Sensing alternating current...

Externet

Well-Known Member
Hi. :)
If a wire conducting alternating current passes trough the square hole inside this red coil below; will a voltage show at the coil terminals ?
1632854710662.png





If a wire conducting alternating current passes trough the round coil hole below; will a voltage show at the coil terminals ?


1632854856451.png

Yes on both,
Only the round,
Only the square,
On none.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Both of course, the shape makes little difference - however, the upper one if intended for low frequencies (50Hz etc.), and the lower one for high frequencies (100KHz+?).

If you drop a magnet through them you will get a pulse - simple school physics.
 

AnalogKid

Well-Known Member
Most Helpful Member
If you put a wire through the coil with the square hole, you won't get much voltage, if any. You need the wires to be vaguely parallel to induce voltage.
1. Not to be pedantically picky, but you induce current, not voltage.

2. Don't think so. Here are links to through-the-hole current sensors and current sense transformers.



ak
 

Diver300

Well-Known Member
Most Helpful Member
1. Secondary current will only flow if there is a secondary load. Voltage is induced by changing magnetic field. There does't have to be an induced current. https://en.wikipedia.org/wiki/Faraday's_law_of_induction

2. In through-the-hole current sensors and current transformers, there is a magnetic core going around the hole, and the sensing wires also go through the hole. In the first picture in post #1, it is a coil designed to have a magnetic core going through the middle. It is possible to add a seconds winding, but that would also have to be around the core, not along the core.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Diver is spot on, no functional output from the first one, the second would work (as a current transformer, most likely).

Think of it as coupled windings - extra turns in common axis to existing ones, for both to share a magnetic field that follows the same path.
No commonality with the first square one, but there is with the toroid.
 

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