currently i am doing a project work on speed control of ac motor by variable frequency method.so i need some help on the general layout of the electronics used to control the speed.
WHY? do you already have one? if not you should be looking at a BLDC instead, they are more efficient and easier to drive.
Induction motors require a lot more processing power to keep 3PH sine waves running instead of just having switching waveforms driving the motor at the drive frequency.
Brush Less Direct Current. they are electronically commutated permanent magnet motors. in other words they use transistors instead of brushes and do not require the sinusoidal drive voltages. they are more efficient as well.