big john
Senior Member
- Location
- Portland, ME
So in the past whenever I used to think about AC current flow, I always envisioned it like the electrons were ping-pong-balls hanging from a string: The would only move back and forth as the voltage on the conductor went from positive to negative and back again.
But then I got to thinking about CTs: If you don't pay attention to polarity and install a CT backwards, the AC current flows through it in the wrong direction and will mess up metering. If the current only flowed back and forth, it would be impossible for it to move in the "wrong" direction, because it flows in both directions.
So, now I have to change my mental image: Is the current moving back and forth as the voltage changes, but it's actually moving in one direction more than the other? Think about a ping-pong-ball on a string mounted inside in a moving car.
Is that an accurate analogy? If it is accurate, why would that be? And if it's not, how is it possible for an AC current transformer to tell which direction current is flowing?
-John
But then I got to thinking about CTs: If you don't pay attention to polarity and install a CT backwards, the AC current flows through it in the wrong direction and will mess up metering. If the current only flowed back and forth, it would be impossible for it to move in the "wrong" direction, because it flows in both directions.
So, now I have to change my mental image: Is the current moving back and forth as the voltage changes, but it's actually moving in one direction more than the other? Think about a ping-pong-ball on a string mounted inside in a moving car.
Is that an accurate analogy? If it is accurate, why would that be? And if it's not, how is it possible for an AC current transformer to tell which direction current is flowing?
-John