# Experiment Electrincal Circuits

ECE22
Delta - Wye and Wye - Delta Transformation Experiment
OBJECTIVE
This experiment explores the Delta - Wye and Wye - Delta transformation, and how can
this be used to simplify the analysis of circuits.
DISCUSSION
In solving networks (having considerable number of branches), one sometimes experiences
great difficulty due to many simultaneous equations that must be solved.
However, such complicated network can be simplified by successively replacing delta
meshes by equivalent wye system and vice versa.
Suppose we are given three resistors R12, R23 and R31 connected in delta fashion between
terminals 1, 2 and 3.
So far as the respective terminals are concerned, these three given resistances can be
replaced by the three resistances R1 , R2 and R3 connected in Wye .
Delta
Wye
Delta-Wye Transformation
To convert from Delta to Wye, we use the following equations:
Wye-Delta Transformation
To convert from Wye to Delta, we use the following equations:
PROCEDURE
Wye – Delta Transformation

Construct the circuit shown below. Assume that R1 = 2 kΩ, R2 = 1 kΩ, R3 = 1.5 kΩ,
Ra = 2.5 kΩ, Rb = 500 Ω, and Rc = 1 kΩ.
Ia
Ra
Ib
Rc
Rb
Ic

Set the DC supply output voltage control to minimum then connect it to the circuit. Switch
the DC supply ON and set its voltage to Vs = 10 Volts.

Use the current divider rule to calculate the theoretical currents Ia, Ib, and Ic and to evaluate
on designated tables.

Using a voltmeter, measure the voltage drop Vad, Vbd, and Vcd, and record the values in
the table below. Pay attention to polarity.
Voltage Drop
Measured

Theoretical
Vbd (V)
Measured
Theoretical
Vcd (V)
Measured
Theoretical
Use an ammeter to measure the DC currents Ia, Ib, and Ic, and record the values in the
table below. Pay attention to polarity.
Current
Ia (mA)
Measured

Theoretical
Ib (mA)
Measured
Theoretical
Ic (mA)
Measured
Theoretical
Convert the Wye connection in the above circuit into a Delta connection and draw the
resulting circuit below.
Delta – Wye Transformation

Now construct the circuit shown below. Assume that R1 = 2 kΩ, R2 = 3 kΩ, R3 = 5 kΩ,
R4 = 10 kΩ, R5 = 1.5 kΩ and R6 = 1 kΩ.
I1
R1
R4
R2
R3
I5
R6
R5
I6

Set the DC supply output voltage control to minimum then connect it to the circuit. Switch
the DC supply ON and set its voltage to Vs = 10 Volts.

Calculate the theoretical voltage drop Vad, Vbd, and Vcd and theoretical currents I1, I5, and

Using a voltmeter, measure the voltage drop Vad, Vbd, and Vcd, and record the values in the
table below. Pay attention to polarity.
Voltage Drop
Measured

Theoretical
Vbd (V)
Measured
Theoretical
Vcd (V)
Measured
Theoretical
Use an ammeter to measure the DC currents I1, I5, and I6, and record the values in the
table below. Pay attention to polarity.
Current
I1 (mA)
Measured

Theoretical
I5 (mA)
Measured
Theoretical
I6 (mA)
Measured
Theoretical
Convert the Delta connection in the above circuit into a Wye connection and draw the
resulting circuit below.
Guide Questions
1. Are the results in Delta - Wye Tables (Voltage Drop and Current) close to the values
in Tables Wye – Delta? Why?
2. How does the given circuit in Wye – Delta Transformation differs from the sketch made
in Delta – Wye Transformation?
3. How can Delta – Wye transformation and vice versa important on determining the
voltage drops and currents in a circuit?
END