Hello,

I have been implementing the field oriented control of three phase induction motor. This task can be divided into two main subtasks:

a) sampling stator phase currents and dc bus voltage

b) generating pwm signals for the IGBT transistors in the three phase inverter

I am going to implement the above mentioned subtasks in following manner. The sampling period will be fixed and there will be two operating modes as far as pwm. In the first operating mode the pwm time base and sampling of the analog inputs will be independent to each other and the carrier signal for pwm will be randomly changed (random carrier pwm scheme). In the second operating mode the pwm time base and sampling of the analog inputs will be synchronized. 

I am able to implement either the first operating mode or the second operating mode but I am not able to figure out how to implement transitions between both operating modes of the pwm. Does anybody have any idea how to resolve this? Thanks in advance for any suggestions. 

#pwm