In a steady state regime we want to supply the load with voltages that form a balanced tri phased system of sinusoidal voltages:
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In the case of the sine wave modulation we consider:
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As we must have
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the voltages 
must have a peak amplitude U0 so that
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We can write
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which leads to:
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The coefficient r is called the amplitude modulation factor
If we normalize the amplitude of the reference voltages, that means if 
, we'll obtain:
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Figure 2
