Hi all

first thread and all that, it's gonna have to be a question [Linked Image]

here is my problem. I want to control an AC induction motor using PWM, so far i think i will Rectify the AC so it becomes a nice DC voltage then generate 20KHz or higher PWM pulse using a PIC16 or PIC18, and an oscilator to control the speed (manual control). then the PWM goes onto the Switches which are going to be a Half Bridge Transistor Bridge. and hopefully it will work like a treat.

Now questions: 1) Are there an Tansistors out there thats say about $10 and can do high power (600watts or so) and can they be switch at 20KHz? 2) if i can avoid it, i really don't want to use MOSFET due to their prices, unless you can find me some really cheap ones. and lastly 3) do i need full bridge? as the motor only really need to go forward and stop.

thanks for any sort of help.

cheerio