Understanding VBase and ZBase: The Relationship Between IActual and IBase

[tim9000]

If you took: V_Base / Z_Base

does that give you I_Actual

or I_Base or what?

Because it seemed to give me I_Actual.

Cheers

 

[Simon Bridge]

What is the difference?

 

[tim9000]

What is the difference?

Like if I_actual = I_base*I_{per unit}

 

[Simon Bridge]

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?

 

[tim9000]

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 V_base / Z_base = (V_actual/V_pu) / (Z_actual/Z_pu)
=V_actual * Z_pu / V_pu*Z_actual = I_actual * (Z_pu/Z_actual)
But I'm not sure what that means for the last part of the last term

 

[Babadag]

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

 

[tim9000]

Iactual * (Zpu/Vpu)=Iactual*Ipu

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

so V_base / Z_base = I_actual / I_pu ?
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
I_base = √(S_base - Z_base) ?

 

[Babadag]

Sorry again. My mistake, this time : Vbase / Zbase = Iactual / Ipu, indeed.

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