Hello,Sorry first for my poor English.
I have a Brushless DC Motor with 400 watts power.
I want to control its speed under nominal speed.
What is the cheapest way to control it?
Very thank you.
Do you have a link to the motor? Or a make and model?
Weedpharma
I have the Motor and I want to control its speed under nominal speed.
tnx.
As per previous posts, get an ESC
Leon, how about sharing the link, make, model with us. So we know what type it is.
Weedpharma
Is it an RC motor ? That's like a 30 to 35 A motor running on a 3S lipo. Not much. I have a 75A motor running off a 4S on my Stryker aircraft. (1200 W).
I have the Motor
Post a link for the motor.
Can I control it with the PWM or SPWM without any buck or boost under nominal speed.
Thanks.
what makes you think people will answer your question while you don't answer theirs ?
you'be been asked 3 times to give information about the motor ..... 
Post the motor information and we'll tell you how to control the ESC. (it's not PWM).