Three winding transformer

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Discussion Overview

The discussion revolves around the function of the tertiary winding in a three-winding transformer, specifically focusing on the behavior of zero sequence currents and their interaction with primary and secondary currents. Participants are exploring the implications of isolated neutral connections and the balancing of currents in this context.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the statement regarding the inability of primary currents to balance the zero sequence component caused by line-to-neutral loads on the secondary side.
  • Another participant prompts a discussion about the phase relationship of zero sequence currents and their implications for current flow into the neutral node.
  • It is noted that zero sequence currents are in phase with each other, but there is confusion about why primary currents cannot balance these currents.
  • Further inquiry is made into the implications of an isolated neutral and whether this affects the ability of currents to return to the neutral node, referencing Kirchhoff's current law.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the balancing of zero sequence currents and the role of the isolated neutral in this context. Multiple viewpoints are presented, and the discussion remains unresolved.

Contextual Notes

The discussion highlights potential gaps in understanding the basic principles of current flow in transformers, particularly regarding the definitions and implications of zero sequence currents and isolated neutrals.

Who May Find This Useful

Individuals studying electrical engineering, particularly those interested in transformer design and operation, may find this discussion relevant.

ranju
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while studying the purpose of tertiary winding in the this 3-winding transformer , I'hv gone through a statement that " the zero sequence component caused by line-to-neutral load on secondary side cannot be balanced by primary currents as the zero sequence currents cannot flow in isolated neutral star connected primary".
Now first of all I wanted to know that the currents in secondary are balanced by primary as this is the basic thing I am not getting this and why can't primary currents balance the zero sequence component ??
And secondly why can't the zero sequence current flow in star-primary??
I am missing some basics , so please elaborate it..??
 
ranju said:
zero sequence currents cannot flow in isolated neutral star connected primary"

Isolated neutral... hmmmmm,,, you already know the answer...

What is phase relation between zero sequence currents?

What does KCL tell you about currents into that neutral node?
 
jim hardy said:
What is phase relation between zero sequence currents?
the zero sequence are all in same phase with each other & there's a zero phase displacement between them .. I am not getting why the primary currents can't balance the zero sequence current??
 
ranju said:
the zero sequence are all in same phase with each other & there's a zero phase displacement between them .. I am not getting why the primary currents can't balance the zero sequence current??
hmmmmm. all in phase? Do they all flow into or out of the the neutral in phase?

seems there's no way back out of neutral? You said it's not connected ... Kirchhoff says what goes in must come back out?
 
Last edited:

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