Chapter 9 – Sinusoids and Phasors Sinusoid – a cosine or sine function Vm = amplitude ω = angular frequency = 2πf = 2π/T Φ = phase angle usually in degrees!
Sum of Sine and Cosine:
Phasor A complex number representing the amplitude and phase angle of a sinusoid. Complex Number Representation: Rectangular Polar Exponential
Algebra of Complex Numbers:
Summary: Addition or Subtraction: Rectangular Multiplication, Division, Exponents and Roots: Polar or Exponential
How is a phasor related to a sinusoid? Recall: where:
Phasor Transformations:
Phasor Differentiation and Integration:
Example 1. Using the phasor approach find the solution to the integro-differential equation:
Complex Impedance Element Impedance – ratio of phasor voltage to phasor current
Consider Parallel RLC Time domain Phasor
In General: Element Admittance In General:
Network Reduction:
Procedure: Transform sinusoidal time functions to phasors, and convert element to complex impedance/admittance. Apply network reduction, or other circuit principles (KVL, KCL, nodal, mesh, etc.) to determine desired response in phasor form. Transform results to time functions.
Example2. Find: vo(t) Current in resistor.