First off, I have very little knowledge in electrical engineering and my last official contact with the subject was when I was in high school so go easy on me.
I am trying to understand if it's possible to control speed and torque on a motor (BLDC specifically) like changing gears in a car. I know that PWMs are used like a throttle; but to change the torque and speed characteristics, is it possible to use multiple transformers? For example. For the same power, a high voltage and lower current will give you greater speed with little torque, like a high gear in the transmission where as high current and lower voltage can you give you high torque and low speed, like a low gear in the transmission.
The idea is that if I have an electric vehicle, I could use a small battery to generate more torque/speed than the same motor with a bigger battery where the max speed and torque is fixed.
Is this idea flawed? If not is there a used case?