1) Grid power supplies single phase, 120 or 240 volt AC power at 60 hz

2) That power is run through diodes to create 120 volt or 240 volt direct current

3) A microprocessor connected to three sets of IGBTs (essentially high power transistors) switches them on an off to create three phase power at a variable frequency

4) The three phase, variable frequency AC electricity drives a three phase motor – no losses from shaded poles or starting coils – or coasting between the two poles

5) By varying the frequency of the AC, you vary the speed of the AC motor efficiently

6) Also, you can have smaller coils if you drive the motor at a higher frequency then gear the motor down for power and speed desired