Friday 14 February 2014

Star To Delta Transformation Or Star To Delta Conversion And Formulas

STAR TO DELTA TRANSFORMATION OR STAR TO DELTA CONVERSION AND FORMULAS

Fig:-
transformer connection diagram formula

Suppose, RA  , RB and RC is three resistances connecting to each other such that they forms a star connections or star networks.

 Now, we have to convert this circuit in delta for solving or simplifying given star connected circuits. Because if you are not convert may not get equivalent resistances of that given circuit.

Fig:-
3 phase transformer calculation formulas

So, we make a delta connection. Connecting pt.1 to pt.2 and pt.3 and also connecting pt.2 to pt.3. It will form a new network as ‘delta connection’ as I shown through dotted diagram and hence forms a new ‘Delta circuit’.

For new circuits containing new resistances is R12  , R13 and R23 having new value’s. For these new resistances we have direct formula’s I am going to give you because no need of derivation, kindly used direct formulas as given below:-

Fig:-
3 phase transformer calculator

How to remember?

The equivalent delta resistance between any two terminals is given by the sum of star resistances between those terminals plus the product of these two star resistances divided by the third star resistance”.

Sunday 16 December 2012

Solved Problem Based On Maximum Power Transfer Theorem

Solved Problem Based On Maximum Power Transfer Theorem
Ques.) Find the value of RL for the given network below that the power is maximum? And also find the Max Power through load-resistance RL by using maximum power transfer theorem?
Solved Problem Based On Maximum Power Transfer Theorem
Solution: -
steps to solve maximum power transfer theorem

For the above network, we are going to find-out the value of unknown resistance called “RL”. In previous post, I already show that when power is maximum through load-resistance is equals to the equivalent resistance between two ends of load-resistance after removing.
So, for finding load-resistance RL. We have to find-out the equivalent resistance like that for this circuit:-
maximum power transfer theorem with dependent sources
maximum power transfer theorem with dependent sources
maximum power transfer theorem experiment
Now, For finding Maximum Power through load-resistance we have to find-out the value of Vo.c.
Here, Vo.c is known as voltage between open circuits.
So, steps are:-
maximum power transfer theorem proof
For this circuit using Mesh-analysis. We get
Applying Kvl in loop 1st:-
6-6I1-8I1+8I2=0
-14I1+8I2=-6         ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ (1)
Again, Applying Kvl in loop 2nd:-
-8I2-5I2-12I2+8I1=0
8I1-25I2=0             ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ (2)
On solving,eqn (1) & eqn (2), We get
I1 = 0.524 A
I2 = 0.167 A
Now, From the circuit Vo.c is
VA-5I2- VB = 0
Vo.c/ VAB= 5I2 = 5X0.167 = 0.835v
So, the maximum power through the RL is given by:-
maximum power transfer theorem for ac circuits pdf