I've been researching making a driver for a 3 phase induction motor powered by DC source using PWM to approximate sine waves in each phase.

However, the switching speeds of the PWM signal for the rotational speed I want is difficult to obtain with hobby microcontroller boards like the arduino.

Can I just switch the DC directly thru each phase at the correct time only twice per cycle ?  Essentially I would be approximating a sine wave with only 2 different voltages thru the coils, ie: +V and -V (using H bridge circuitry here)

Will this create enough of a rotating magnetic field that sufficient current is induced in the rotor cage ?

What will be the losses in power / efficiency for this, or any other drawbacks for this system ?

The bonus is greatly simplified drive electronics.


Question: cancel(getIntent().getExtras().getInt(“notificationID”)); what is the return...?
Answer: You should try going through the concepts of object oriented programming first.

To answer your question, getIntent() returns an object of type intent. We call the getExtras() on the Intent object which returns an object of type Bundle. Then we call getInt() on the Bundle object to finally get the int we want to pass to the cancel() method.

The statement is equivalent to :

Intent i = getIntent();
Bundle b = i.getExtras();
int id = b.getInt("notificationID");
cancel(id);


If we don't need any of the intermediate objects, we can write the whole thing in a single line.

Hope that helps.