example 1 example 2 allowed not allowed example 3
TRANSCRIPT
Lecture 4
Notes in Voltages Sources , Current Sources, and Star - Delta transformation
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Example 1
Example 2Allowed
Not Allowed
Example 3
Example 4
Example 5Allowed Not Allowed
Current Sources in Series
Series and Parallel SourcesVoltage sources in series can be combined into
a single voltage source:
Current sources in parallel can be combined into a single current source:
Ia + Ib + Ic
Va+Vb+Vc
Va
Vb
Vc
Ia Ib
Ic
Independent SourcesIndependent voltage
source
maintains the prescribed voltage across its terminals regardless of the current drawn from it
Independent current source
maintains the prescribed current through its terminals regardless of the voltage across those terminals
“Controlled” or “Dependent” Sources
• A voltage or current source whose value “depends” on the value of voltage or current elsewhere in the circuit
• Use a diamond-shaped symbol
Dependent Voltage Sources
+–
6Vx
Voltage-Controlled Voltage Source (VCVS)
6000Ix
Current-Controlled Voltage Source (CCVS)
+–
Dependent Current Sources
0.006Vx
Voltage-Controlled Current Source (VCCS)
6Ix
Current-Controlled Current Source (CCCS)
Practical Dependent SourcesOperational amplifiersTransistors
Bipolar Junction Transistors (BJTs)Metal-Oxide-Semiconductor Field Effect
Transistors (MOSFETs)Voltage and current regulatorsOther devices include:
Photodetectors, LEDs, and lasersPiezoelectric devicesThermocouples, thermovoltaic sources
Star - Delta Transformation:
a
bc
a
bc
R a
R bR c
R 1 R 2
R 3
(a ) w ye c o n fig u ra tio n (b ) d e lta c o n fig u ra tio n
a
accbba
c
accbba
b
accbba
R
RRRRRRR
R
RRRRRRR
R
RRRRRRR
3
2
1
321
31
321
32
321
21
RRR
RRR
RRR
RRR
RRR
RRR
c
b
a
Q: Find the resistance between the points E and F ?
Solution
•Ans. : 5.6 Ω
Home WorkQ 1 : Find Rab and I
?
13
100 V
50
10
i a
b Figure 2.54
Q2 : Use -to-Y transformation to find the voltages v1 and v2 ?
1 10
24 V
15
+V1-
+V2-
Q 3 :Find the total resistance in the circuit below?