Basic_Electrical_Engineering_4th_edition

1 44					3 x 10 -		ELECTRICAL ENGINEERING
Current supplied by the battery
			10	-		15	A
			4 + 4/3		16	8
Current through 2 Q resistor
			15	4	5
			- X	- =	- A
			8	6	4
Total current through		AB 5 +		4	4 A
			is
				5	25
				- =	-
The Norton's equivalent circuit, therefore is							2 Q
		4	A			2 Q
		25
					Fig. E 2.1 5.2
	through			branch is
Therefore, current			425ABx 2=1		S25 = 3.125 A

2.9 MAXIMUM POWER TRANSFER THEOREM

Sometimes in electronics circuits it is desirable to transfer maximum power through a source to a load e.g. impedance matching is carried out in a loud speaker so that maximum sound could be heard. However in power system maximum power transfer is never tried as huge amount of power in terms ofMW are transferred from source to the load and the efficiency of transfer is 50% as will be seen shortly ifpower transferred is based on maximum power trans­ fer criterion. Also under this, the terminal voltage becomes half of the source voltage and hence this results in poor voltage regulation, therefore, maximum power transfer criterion is never considered in power system.

We will consider the theorem both for d.c. and a.c. circuits. d.c. circuits :

Fig. 2.10 Maximum power transfer-d.c. circuit.