# Three phase transformer

Discussion in 'Homework Help' started by TheSpArK505, Nov 8, 2014.

1. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
Hi everyone.

In a three phase system>>
do the y and delta have same magnitudes of voltage and current as follows ?
line i (delta)= phase i (y)
phase v (delta) = line v (y)

and what are the turn ratios of
1.y-delta
2.delta-y
referred to the primary side.

2. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
You need to go look at the definitions of line and phase quantities carefully and then I would recommend that you derive the relationships between them for yourself and compare those to what your text gives.

3. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
Actually i asked these questions because they are not mentioned in my text book

4. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
Okay, so what are the definitions of line current, line voltage, phase current, and phase voltage that you ARE given.

5. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
i know that in y phase and line currents are equals and line voltage = sqrt(3)* phase voltage <30
i also know about voltage and current of delta....But i'm asking about the specific equivalents i the top!!!

6. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
But I'm not asking about equivalents in A y or A delta alone. I'm asking about some values(of Is or Vs) that are equivalent when i have a mixed system of y and delta system !!

7. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
I'm not asking for equations, but for definitions. The following figure might help the discussion along:

Let's start from the basics and the basics are to be sure that you understand what is meant by the following terms:

1) Line voltage
2) Line current
3) Phase voltage
4) Phase current

As noted, all of the voltages in the diagram are referred to "ground". In general, these may or may not be balanced loads, we can't automatically assume that Vn is the same as ground. But your question, whether you realize it or not, is based on the assumption of a balanced load, but let's get to that in due course.

For each circuit, in terms of the parameters in the diagram, identify the line and phase quantities.

If these are equivalent (but not necessarily balanced) circuits, which of these quantities are the same between circuits?

8. ### upopads2 Member

Sep 20, 2014
52
1
woah Wbahn is incredible.

9. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
phase v (delta) = line v (y) -why is it wrong???
and for Mr.WBahn i do know what are the definitions of line and Phase i.e Vab -Vbc Vca are line voltages in wye and are phase in delta
i also know the rest ....but I'm asking these questions to interpret the equations of the three phase transform

10. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
so is it true that for delta
VAB is a line voltage and VAN is a phase voltage & also Ia is a line current and IAB is a phase current???