Hi there!
I am currently new to this forum, and not too experienced with electronics, so please do not shun my ignorance. For a project I am working on I need to control the speed of a high voltage motor. I was thinking of using a micro controller and a MOFSFET to control the speed through PWM. The problem is, I am not sure what micro controller to get. Also, if there is a more efficient way to use high voltage PWM, I would love to hear your ideas.
One thing you didn't mention till now is the type of motor you'll be controlling. I assumed that you were talking about a high-voltage DC motor, but you could have other motors in mind. You should mention which type of motor you'll be controlling.
If it's a simple high-voltage DC motor, the microcontroller will only generate the PWM signals and will be powered off a low-voltage regulated supply. So, like mentioned above, just about any microcontroller would do. Other features you wish to include, such as display (speed, power, etc), protection (over-voltage, over-current, short-circuit, etc) or any additional features you'll include, will affect your microcontroller choice as then you need to think about the number of I/O pins and the microcontroller peripherals.
If it's an induction motor, for example, you might want to use microcontrollers with dedicated PWM peripherals designed for motor control applications. For simple one-phase motor control, you can use the PWM module in a PIC or AVR. For greater control of the motor and for more complex control, eg for 3-phase induction motor control, you might want to use microcontrollers designed with special 3-phase PWM modules, such as the dsPIC33FJxxMCxxx series of microcontroller (eg dsPIC33FJ12MC202).
You need to choose a good MOSFET driver circuit. This should be rather simple. You can use dedicated drivers such as TC427 (if only low side drive is required) or IR2110 (if both high and low-side drive are required). You could also build simple drivers based on discrete transistors, depending on drive requirements.
You might choose to include isolation. In that case, choose good optically-isolated drivers. Some drivers you can look at include TLP250, TLP350, HCPL3120.
Use MOSFETs with high enough voltage rating, high enough current rating and low on-state drain-source resistance (Rdson).
Hope this helps.
Tahmid.