Understanding VBase and ZBase: The Relationship Between IActual and IBase

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Discussion Overview

The discussion revolves around the relationship between VBase, ZBase, IActual, and IBase in the context of electrical engineering concepts, particularly focusing on per unit systems and their implications. Participants explore the mathematical relationships and definitions associated with these terms.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant questions whether VBase divided by ZBase results in IActual or IBase, suggesting it seems to yield IActual.
  • Another participant seeks clarification on the differences between IActual and IBase, proposing a relationship involving per unit values.
  • A participant presents a mathematical relationship: VBase / ZBase = (VActual/Vpu) / (ZActual/Zpu) and expresses uncertainty about the implications of the final term in the equation.
  • One participant corrects a previous statement, asserting that IBase = VBase / ZBase leads to IActual * (Zpu/Vpu) and connects it to IActual * Ipu.
  • Another participant suggests that (Zpu/Vpu) equals 1/Ipu, leading to the conclusion that VBase / ZBase equals IActual / Ipu.
  • A side question is raised regarding the calculation of IBase from rated power and voltage, specifically whether IBase equals the square root of (SBase - ZBase).
  • Further clarification is provided that for a single-phase system, IBase can be expressed as the square root of (SBase/ZBase).

Areas of Agreement / Disagreement

Participants express uncertainty and seek clarification on the relationships between the variables, with no consensus reached on the implications of the equations or the correctness of the derived relationships.

Contextual Notes

Some participants acknowledge potential errors in their calculations and the need for further exploration of the relationships between the base and actual values, indicating that assumptions about definitions and contexts may affect the discussion.

tim9000
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If you took: VBase / ZBase

does that give you IActual

or IBase or what?

Because it seemed to give me IActual.

Cheers
 
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What is the difference?
 
Simon Bridge said:
What is the difference?
Like if Iactual = Ibase*Iper unit
 
OK... so do that for the other "base" units.
Remember what the base and per unit parts mean.
What is the relationship between actual things?
 
Simon Bridge said:
OK... so do that for the other "base" units.
Remember what the base and per unit parts mean.
What is the relationship between actual things?
Well I know that Vbase / Zbase = (Vactual/Vpu) / (Zactual/Zpu)
=Vactual * Zpu / Vpu*Zactual = Iactual * (Zpu/Zactual)
But I'm not sure what that means for the last part of the last term
 
Sorry, the final term is wrong here:

Ibase=Vbase / Zbase = (Vactual/Vpu) / (Zactual/Zpu) =Vactual * Zpu / (Vpu*Zactual) = Iactual * (Zpu/Vpu)

Iactual * (Zpu/Vpu)=Iactual*Ipu
 
Babadag said:
Iactual * (Zpu/Vpu)=Iactual*Ipu

Oh right.
but Isn't (Zpu/Vpu) = 1 / Ipu

so Vbase / Zbase = Iactual / Ipu ?
Also, side question, say you were given the rated power and voltage for a system, so then you can work out the rated base impedance. But does that mean that
Ibase = √(Sbase - Zbase) ?
 
Sorry again. My mistake, this time : Vbase / Zbase = Iactual / Ipu, indeed.

Also for single phase system Ibase=sqrt(Sbase/Zbase) .So, what further?
 

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