The advantage of the drive topology shown in Figure 5 is the same hardware can be used to control the speed of a 3-phase induction motor. In order to control a 3-phase induction motor with a Variable Frequency (VF) technique, three pairs of complementary PWMs with dead band are required.
The DC bus is modulated with these PWMs to give three Sine voltage outputs with 120 degrees phase shift to each other as shown in Figure 12. This can be done by changing the offset pointers on the Sine table. Firmware needs to be recompiled and the part should be reprogrammed. To reverse the motor direction, the PWM loaded to two of the phases should be interchanged.
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