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power_fftscope - Perform Fourier analysis of signals stored in Structure with Time format

Syntax

power_fftscope
sps = power_fftscope('sys')

Description

power_fftscope opens the FFT Analysis Tool dialog box to perform Fourier analysis of signals stored in a Structure with Time format. The dialog box provides an easy access to all the Structure with Time variables defined in your workspace. This tool can also be activated from the Powergui block dialog box by selecting FFT Analysis.

sps = power_fftscope('sys') returns the current FFT settings and results for the signal displayed in the dialog box. fftdata is a structure with the fields:

Field	Description
structure	The name of the Structure with Time variable that contains the analyzed signal
input	The input signal of the selected Structure with Time variable
signal	The index of the selected input signal specified by the input field
StartTime	The start time of the FFT window
cycles	The number of cycles of the FFT window
fundamental	The fundamental frequency of analyzed signal
MaxFrequency	The maximum frequency evaluated by the FFT analysis
FFTdata	The analyzed signal (FFT window data)
mag	Computed magnitude of FFT
phase	Computed phase of FFT
freq	Frequency vector
THD	The computed Total Harmonic Distortion for the analyzed signal

Dialog Box

Display selected signal

If selected, display in the upper plot the signal selected by the Structure, Input, and Signal number parameters.

Display FFT window

If selected, display in the upper plot the portion of the selected signal where the FFT analysis is performed.

Structure

Lists the structures with time variables that are present in your workspace. You first need to run a simulation of your model. These structures are generated by the Scope or To Workspace blocks in your model. The signals must be sampled at a fixed rate, by using the Scope block settings. Use the pull-down menu to select the variable you want to analyze.

Input

Select the input signal of the selected structure with time variables specified in the Structure field. Structures with time variables with multiple inputs can be generated by a Scope block having multiple input ports.

Signal Number

Specify the index of the selected input signal specified by the Input parameter. For example, the Signal Number parameter allows you to select the phase A signal of a three-phase signal connected to input 2 of a Scope block.

Start time(s)

Specify the start times for the FFT analysis. The FFT analysis will be performed on the portion of the signal starting at the specified time and for the specified number of cycles.

Number of cycles

Specify the number of cycles of the selected signal to analyze for the FFT analysis.

Fundamental frequency

Specify the fundamental frequency, in hertz (Hz), as a reference frequency for the FFT analysis.

Display style

In the pull-down menu, select Bar (relative to fundamental) to display the spectrum as a bar graph relative to the fundamental frequency. Select Bar (relative to specified base) to display the spectrum as a bar graph relative to the base defined by the Base value parameter.

Select List (relative to fundamental) to display the spectrum as a list in % relative to the fundamental or DC component. Select List (relative to specified base) to display the spectrum as a list in % relative to the base value defined by the Base value parameter.

Base value

Enter a base value for the display of harmonics.

Frequency axis

In the pull-down menu, select Hertz to display the spectrum frequency axis in hertz. Select Harmonic order to display the spectrum frequency axis in harmonic order relative to the fundamental frequency.

Max Frequency

Specify the maximum frequency, in hertz (Hz), for the FFT analysis.

Display

Display in the lower plot the FFT analysis results for the selected measurement.

Close

Close the FFT Analysis Tool window.

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