Download presentation
Presentation is loading. Please wait.
Published byLeonard Webster Modified over 8 years ago
1
ELECTRIC CIRCUITS EIGHTH EDITION JAMES W. NILSSON & SUSAN A. RIEDEL
2
CHAPTER 10 SINUSOIDAL STEADY – STATE POWER CALCULATIONS © 2008 Pearson Education
3
CONTENTS 10.1 Instantaneous Power 10.2 Average and Reactive Power 10.3 The rms Value and Power Calculations 10.4 Complex Power 10.5 Power Calculations 10.6 Maximum Power Transfer © 2008 Pearson Education
4
10.1 Instantaneous Power Instantaneous power is the product of the instantaneous terminal voltage and current, or © 2008 Pearson Education The black box representation of a circuit used for calculating power
5
The positive sign is used when the reference direction for the current is from the positive to the negative reference polarity of the voltage. The frequency of the instantaneous power is twice the frequency of the voltage (or current). © 2008 Pearson Education 10.1 Instantaneous Power
6
Instantaneous power, voltage, and current versus ωt for steady-state sinusoidal operation © 2008 Pearson Education 10.1 Instantaneous Power
7
10.2 Average and Reactive Power Average Power Average power is the average value of the instantaneous power over one period. It is the power converted from electric to non-electric form and vice versa. © 2008 Pearson Education
8
10.2 Average and Reactive Power This conversion is the reason that average power is also referred to as real power. Average power, with the passive sign convention, is expressed as © 2008 Pearson Education
9
Reactive Power Reactive power is the electric power exchanged between the magnetic field of an inductor and the source that drives it or between the electric field of a capacitor and the source that drives it. © 2008 Pearson Education 10.2 Average and Reactive Power
10
© 2008 Pearson Education 10.2 Average and Reactive Power Reactive Power Reactive power is never converted to nonelectric power. Reactive power, with the passive sign convention, is expressed as
11
© 2008 Pearson Education 10.2 Average and Reactive Power Instantaneous real power and average power for a purely resistive circuit
12
Instantaneous real power, average power, and reactive power for a purely inductive circuit © 2008 Pearson Education 10.2 Average and Reactive Power
13
Instantaneous real power and average power for a purely capacitive circuit © 2008 Pearson Education 10.2 Average and Reactive Power
14
Power Factor Power factor is the cosine of the phase angle between the voltage and the current: © 2008 Pearson Education 10.2 Average and Reactive Power
15
The reactive factor is the sine of the phase angle between the voltage and the current: © 2008 Pearson Education 10.2 Average and Reactive Power
16
10.3 The rms Value and Power Calculations A sinusoidal voltage applied to the terminals of a resistor Average power delivered to the resistor © 2008 Pearson Education
17
The average power delivered to R is simply the rms value of the voltage squared divided by R. If the resistor is carrying a sinusoidal current, the average power delivered to the resistor is: © 2008 Pearson Education 10.3 The rms Value and Power Calculations
18
10.4 Complex Power Complex power is the complex sum of real power and reactive power. A power triangle © 2008 Pearson Education | S | = apparent power P = average power Q = reactive power θ
19
10.4 Complex Power Three power quantities and their units © 2008 Pearson Education QuantityUnits Complex powervolt-amps Average powerwatts Reactive powervar
20
Apparent Power is the magnitude of complex power. © 2008 Pearson Education 10.4 Complex Power
21
10.5 Power Calculations © 2008 Pearson Education The phasor voltage and current associated with a pair of terminals
22
10.6 Maximum Power Transfer A circuit describing maximum power transfer © 2008 Pearson Education
23
10.6 Maximum Power Transfer The circuit with the network replaced by its Thévenin equivalent Condition for maximum average power transfer © 2008 Pearson Education
24
10.6 Maximum Power Transfer Example: Determining Maximum Power Transfer without Load Restrictions. a)For the circuit shown below, determine the impedance Z L that results in maximum average power transferred to Z L. b)What is the maximum average power transferred to the load impedance determined in (a)? © 2008 Pearson Education
25
THE END
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.