- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Try listing your phase angles again please. The return current on the neutral as sourced by PV on L1 will be in the same direction as the return current on the neutral from the load on L2. So they do add. All the way back to the POCO transformer, but not into the primary side of the POCO transformer. If you really have a center tapped winding on one core, there will be no current on the primary side. It is true that the power flows from PV to load, but that does not mean that the current does the same thing!.I was wondering if anyone was going to comment on that post :huh:
No wrong assumptions on my part. PV L2 is zero amperes and degrees to the utility. What you marked in red is via POCO transformer... but it is same current that originated from PV L1. It then goes through the load then back to PV L1 via the neutral. There is no additive neutral current.
(The normal current you show at zero degrees on L1 is of zero amplitude, so I assume that you just drew it for reference.)
If you have 30A going into the transformer secondary at L1 and 30A going into the transformer secondary at L2, you cannot just get rid of them both by showing them going to the primary.
voltage (phase) polarities and then in addition say that there is another 180 phase shift because of the direction of the arrow.
The load current at L2 is at 180 degrees to the voltage at L2, not to the voltage at L1.
At the point in the cycle where L1 is positive with respect to the neutral, current will flow toward the transformer through L1 and will flow toward the transformer through L2 (which is negative at that point in time) from the load. That leaves double the current to come back through the neutral.
How I wish I could draw animated pictures. <sigh>
If you look at the two halves of the center tapped secondary as two separate windings on an autotransformer (or an isolation transformer for clarity), you will see that the current will be flowing in the same direction relative to the midpoint in both windings. That allows the magnetic fields of the two windings to cancel in the core (not counting magnetization current for now.)
PS: I can see how you try to justify your error, and I sympathize, but you are still wrong.
Last edited: