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INC 112 Basic Circuit Analysis. Week 13 Frequency Response. Frequency Response. What is the change of vL(t) when the frequency of the voltage source change?. |vL| (magnitude). A. ω. Log scale of frequency. |vL| (magnitude). A. Log ω. Linear Scale & Log Scale. Linear Scale. 6. 5.
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INC 112 Basic Circuit Analysis Week 13 Frequency Response
Frequency Response What is the change of vL(t) when the frequency of the voltage source change?
|vL| (magnitude) A ω
Log scale of frequency |vL| (magnitude) A Log ω
Linear Scale & Log Scale Linear Scale 6 5 4 1 2 3 Log Scale 1000 100 0.1 1 1000 10
What is the frequency response of vc(t) |vc| (magnitude) A Log ω
Input & Output System Output Input Input is usually what we can control. Output is usually what we are interested in.
What is the frequency response of vc(t) Input = voltage source Output = vc(t)
Frequency Domain Frequency domain is another point of view of things in the world. Some analysis are easier done in frequency domain than time domain.
Metaphor of Frequency Domain Frequency Domain Time Domain (1,1,1) (2,-3,0)
Time Domain Frequency Domain
Transfer Function Transfer function = ratio of output and input in frequency domain Input Output System H(s) U(s) Y(s) Transfer function Note: Transfer function describes characteristic of a system.
Example: Obtaining Transfer Function input isv(t) output isvc(t)
Change all components to Phasor (frequency domain)
Frequency Response System Output Input Freq 10Hz Amplitude = 0.96 Phase = 12 Freq 100Hz Amplitude = 0.82 Phase = 44 Freq 800Hz Amplitude = 0.53 Phase = 56 Freq 10Hz Amplitude = 1 Phase = 0 Freq 100Hz Amplitude = 1 Phase = 0 Freq 800Hz Amplitude = 1 Phase = 0
Frequency Response Plot Magnitude Phase Note: log frequency and log magnitude
The HP 35670A Dynamic Signal Analyzer obtainsfrequency responsedata from a physicalsystem.
Fourier Series “Any periodic signal can be written in the sum of sine wave signals at different frequency.”
Cut-off frequency Filter We want to get rid of the signal 3sin(9t) |vc| (magnitude) ω=5 Log ω
Example Find vc(t) Use superposition to consider the effect of two different frequencies
Power Line Systems 3 phases systems have three wire called “line” which are sine wave with phase shift 120 from each other Line 1 Line 2 Line 3 Power Plant 3 phases, 3 wires
Power Plant Line 1 Line 2 Line 3 Neutral 3 phases, 4 wires L1-N = 220Vrms, L2-N = 220Vrms L3-N = 220Vrms L1-L2 = 381Vrms, L2-L3 = 381Vrms, L1-L3 = 381Vrms
Star Connection ( Y-connection) Load Each load get 220 Vrms
Delta Connection ( Δ-connection) Load Each load get 381 Vrms