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When a three phase motor in running and you clamp an amp-meter around all three of the phase wires, you should expect to read zero because the magnetic fields cancel each other out.

I'm having trouble visualizing the process of fields canceling each other out in this scenario. It makes sense to me for two wires carrying AC current in opposite directions that are lying parallel to each other. But for three phases, I don't understand how all three fields are canceled.

Some insight into this would be appreciated!

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    \$\begingroup\$ I had trouble with 3-phase too. It all fell into place once I drew three sine waves, 120 shifted and manually added then up. This was before computers so it was a lot of work which might have helped to really hit home. \$\endgroup\$ – Oldfart Dec 19 '17 at 13:28
  • \$\begingroup\$ You should use phasor representation of fields/currents/signals to visualize the cancelling. See here resultant vector of rotating 3 vectors cancel each other out: electronics-tutorials.ws/accircuits/acp50.gif The vector sum is zero. \$\endgroup\$ – user16307 Dec 19 '17 at 14:05
  • \$\begingroup\$ Is there an alternative link for this .gif? This one does not seem to be functional. \$\endgroup\$ – neerbasu Dec 19 '17 at 17:17
  • \$\begingroup\$ people.ece.umn.edu/users/riaz/animations/vecmovieslow.gif \$\endgroup\$ – JRaef Dec 20 '17 at 0:40
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View your magnetic field vectors as 3 equal length radii inside a circle, set at 0 degrees, +120 degrees, and -120 degrees. The X components cancel, and the Y components cancel.

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