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Comment by declan_roberts

2 years ago

I was trying to figure out exactly how it charges with just 1 pole. It must be induction in that case, right?

From the video description:

> A passively actuated gripping mechanism grasps the powerline cable during landing after which a control circuit regulates the magnetic field inside a split-core current transformer to provide sufficient holding force as well as battery recharging.

When the grippers close they probably close the loops of a coil that wraps around the wire. So it's harvesting the ever changing magnetic field that arises from AC current, independent of voltage. You can still get some power from coils that aren't wrapped around the wire but are still parallel. I think that's how wireless phone chargers work.

You can also take power using a capacitor instead of an inductor, from the changing voltage (not current) in an AC line. Like when you hold a florescent tube vertical under a hi-power line, and it lights up.

  • That is induction though. Acapacitor alone can not extract energy from a ac line. Inductance is what allows energy transfer here.

It could have a small spool of wire to drop to the ground to make contact. This would allow the drone to rest on the wire while charging.