WOLFRAM SYSTEM MODELER

# Rectifier6pulseFFT

Example of FFT block

# Wolfram Language

In[1]:=
`SystemModel["Modelica.Blocks.Examples.Rectifier6pulseFFT"]`
Out[1]:=

# Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

This example is based on a 6-pulse rectifier example, calculating the harmonics with the FFT block.

Sampling starts after the initial transients are settled - waiting for `2 periods = 2/f = 0.04 s = realFFT.startTime`. Choosing a maximum frequency `f_max = 2000 Hz`, a frequency resolution `f_res = 5 Hz` (both given in the block `realFFT`) and the default oversampling factor `f_max_factor = 5`, we have to acquire `n = 2*f_max/f_res*f_max_factor = 4000` sampling intervals. The resulting sampling interval is `samplePeriod = 1/(n*f_res) = 0.05 ms`. Thus, we have to sample for a period of `n*samplePeriod = 1/f_res = 0.2 s`.

The result file "rectifier6pulseFFTresult.mat" can be used to plot amplitudes versus frequencies. Note that for each frequency three rows exit: one with amplitude zero, one with the calculated amplitude, one with amplitude zero. Thus, the second column (amplitude) can be easily plotted versus the first column (frequency). As expected, one can see the 5th, 7th, 11th, 13th, 17th, 19th, 23th, 25th, … harmonic in the result.

# Parameters (6)

V Value: 100 * sqrt(2 / 3) Type: Voltage (V) Description: Amplitude of star-voltage Value: 50 Type: Frequency (Hz) Description: Frequency Value: 0.4 Type: Resistance (Ω) Description: Load resistance Value: 0.005 Type: Capacitance (F) Description: Total DC-capacitance Value: sqrt(3) * V Type: Voltage (V) Description: Initial voltage of capacitance Value: Type: TransformerData Description: Data of transformer 1

# Components (15)

source Type: SineVoltage Description: Polyphase sine voltage source Type: Star Description: Star-connection Type: Ground Description: Ground node Type: CurrentSensor Description: Polyphase current sensor Type: IdealDiode Description: Polyphase ideal diode Type: Star Description: Star-connection Type: IdealDiode Description: Polyphase ideal diode Type: Star Description: Star-connection Type: Resistor Description: Ideal linear electrical resistor Type: Capacitor Description: Ideal linear electrical capacitor Type: Capacitor Description: Ideal linear electrical capacitor Type: Ground Description: Ground node Type: TransformerData Description: Data of transformer 1 Type: Dy01 Description: Transformer Dy1 Type: RealFFT Description: Sampling and FFT of input u