Assignment Polyphase

8/11/2019 Assignment Polyphase

1/23

POLYPHASE CIRCUIT ANALYSIS [BEF23803]

SECTION 1ASSIGNMENT 1

LECTURERS NAME: DR. ERWAN BIN SULAIMAN


2/23

GROUP MEMBERS NAME:

SHARINI A/P P.JANASEKARAN

[CE130108]

NURUL HANIS BINTI MUHAMAD SOBRI

[CE130165]

AZLIN HAZWANI BINTI ROSLEE

[CE130125]


3/23

DISCUSS THE DIRECTION OF

POWER FLOW IN CONVENTIONAL

POWER SYSTEM CIRCUIT


4/23

Direction of Power Flow

It is assumed that a specific load is consuming power. If however we are

generating power, then the direction of the current flows is reversed. But

because the current is alternating, the direction is reversing anyway, 50 or

60 times each second. We need a reference to compare the current

direction against. Fortunately, we have that in the form of the voltage.


5/23

In figure 1, the voltage and current waves both rose and fell together. When thevoltage was positive (above the x axis) then the current too was positive, and when the

voltage was negative (below the x axis) then the current too was negative.

Power is equal to the product of the voltage and current and so the power was always

positiveall of the power curve is above the x axis.

Figure 1Voltage, current, power graph of a resistive load
http://openenergymonitor.org/emon/sites/default/files/resistive2.jpghttp://openenergymonitor.org/emon/sites/default/files/resistive2.jpg


6/23

If the house is generating power, the direction of the current is reversed compared to

how it was before. Now, when the voltage is positive (above the x axis) then the current

is negative (below the x axis), and when the voltage is negative then the current is

positive. The power always negativeall of the power curve is below the x axis.

The sign of the power therefore indicates whether power is being consumed or

generated.

Figure 2Voltage, current, power graph when generating
http://openenergymonitor.org/emon/sites/default/files/revpower.pnghttp://openenergymonitor.org/emon/sites/default/files/revpower.pnghttp://openenergymonitor.org/emon/sites/default/files/revpower.pnghttp://openenergymonitor.org/emon/sites/default/files/revpower.pnghttp://openenergymonitor.org/emon/sites/default/files/revpower.pnghttp://openenergymonitor.org/emon/sites/default/files/revpower.pnghttp://openenergymonitor.org/emon/sites/default/files/revpower.png


7/23

GIVE THE DEFINITION OF

MAXIMUM AVERAGE POWERTRANSFER


8/23

Definition of Max. Average

In the maximum average power transfer theoremstates that the maximum external power from a sourcewith finite internal resistance. The internal resistanceof the load must be equal the resistance of the source

as viewed from its output terminal.

To solved the problem of maximizing the powerdelivered by a power-supplying resistive network to aload RL. Representing the circuit by its Thevenin

equivalent with proved that the maximum powerwould be delivered to the load if the load resistance isequal to the Thevenin RL = RTH.


9/23

EXPLAIN CLEARLY HOW TO FIND

THE MAXIMUM POWERTRANSFER AT THE LOAD USING

THEVENIN EQUIVALENT CIRCUIT


10/23

Find the Max. Power Transfer

Finding the maximum average power which can be transferred from a linear circuit to a loadconnected.

Circuit with a load Thevenin Equivalent circuit

The circuit at the right side represents the circuit to the left of the load by its Thevenin

equivalent.

LoadZLrepresents any element that is absorbing the power generated by the circuit.

Find the Maximum Average Power that will be absorbed by loadZLfrom the circuit to

which it is connected. The entire circuit is replaced by the thevenin equivalent except for

the load.


11/23


12/23


13/23


14/23

EXPLAIN AN EXAMPLE TO SOLVE A

PROBLEM OF MAXIMUM POWER

TRANSFER IN RLC CIRCUIT


15/23

Example of Problem in RLC Circuit

EXAMPLE 1:

Calculate the resistive load needed for maximum power transfer and the

maximum average power.


16/23

EXAMPLE 1:

Calculate the resistive load needed for maximum power transfer and the

maximum average power.


17/23


18/23


19/23

EXPLAIN THE CONDITION OF

MAXIMUM AVERAGE POWER FOR

RESISTIVE LOAD. SOLVE AN

EXAMPLEFOR THE ABOVE CONDITION


20/23

Condition for Resistive Load

When the load is purely resistive, the condition for

maximum power transfer is:

Now the maximum power can not be obtained from the

Pmaxformula.

Maximum power can only be calculated by finding the

power of RL when XL=0.


21/23


22/23

Example of Problem

Determine the load impedance, ZL that maximizes the average power drawn from the

circuit. What is the maximum average power?


23/23

Documents

Assignment Polyphase