Bài giảng Electrical and electronic principles: Chương 3 - ThS. Ngô Quốc Cường

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT

TP. HỒ CHÍ MINH

ELECTRICAL AND ELECTRONIC
PRINCIPLES
WEEK 3

Cuong Q. Ngo


Last classes
• Branch; node; loop
• KCL
• KVL

• Methods of analysis
• Thevenin’s theorem
• Norton theorem

2


CONTENTS (Today)
• T, 𝜋, Y, delta networks

• Network of complex impedance
• Maximum power transfer

3

1. T, 𝜋, Y, delta networks
• Two forms of the same network – Y, T

• Two forms of the same network – ∆, 𝜋

4


1. T, 𝜋, Y, delta networks
• Delta to Wye conversion

5


1. T, 𝜋, Y, delta networks
• Wye to Delta conversion

6


1. T, 𝜋, Y, delta networks
• Convert the network in the figure below to an equivalent Y
network

7


1. T, 𝜋, Y, delta networks
• Answer

8


1. T, 𝜋, Y, delta networks
• Transfer the wye network to delta network

9


1. T, 𝜋, Y, delta networks
• Answer

10


1. T, 𝜋, Y, delta networks
• Obtain the equivalent resistance Rab for the circuit in Figure
below and use it to find current i.

11


1. T, 𝜋, Y, delta networks
• Answer: R = 9.63 Ω

12


1. T, 𝜋, Y, delta networks

• Answer: R = 9.63 Ω

13


2. Network of complex impedance
• Sinusoids

• Phasor
– A phasor is a complex number that represents the
amplitude and phase of a sinusoid.

14


2. Network of complex impedance
• A complex number can be expressed in 3 ways

15


2. Network of complex impedance

16


2. Network of complex impedance
• The impedance Z of a circuit is the ratio of the phasor voltage
V to the phasor current I, measured in ohms.
• The admittance Y is the reciprocal of impedance, measured

in siemens (S).

17


2. Network of complex impedance
• Find v(t) and i(t) in the circuit

18


2. Network of complex impedance
• Answer

19


2. Network of complex impedance
• Exercise 2.1
• Find the input impedance of the circuit. Assume that the
circuit operates at 𝜔 = 50 𝑟𝑎𝑑/𝑠

20


2. Network of complex impedance
• Answer

21

2. Network of complex impedance
• Exercise 2.2
• Determine vo(t) of the circuit

22


2. Network of complex impedance
• Answer

23


2. Network of complex impedance
• Steady state analysis
– Mesh analysis
– Thevenin and Norton equivalent circuit

24


2. Network of complex impedance
• Exercise 2.3
• Find Io using mesh analysis

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