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Complementary Pwm


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#1 Gentleman

Gentleman

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Posted 15 November 2006 - 02:52 PM

Hi,

For generation of 3-phase Sine wave thro a microcontroller, a complementary PWM is used. One wave (direct) feeds the Hi - IGBT and the other wave (complementary) feeds the Lo - IGBT.

Once we set the duty cycle for the PWM channel (1-channel consist of Hi + Lo) to say 10%, the duty cycle of the Hi is set to 10%, while the Lo automatically becomes 90% (since complementary). But both does not turn ON at same time (when Hi ON, Lo is OFF and vice versa).

My query -->
1. If that PWM channel is connected to phase-A, then does it mean that winding in phase - A will source (Current from end to neutral) for 10% and sink (Current from neutral to end) for 90%? In other words, does it mean that when we set the duty cycle as 10%, the phase will actually sinking more current?

2. How do we explain the same for a single - phase sine wave? Do we still need complementary PWM for generating single-phase sine wave?

Thanks.








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