CVT Transmission:
The continuously variable transmission (CVT) is a transmission in which the ratio of the rotational speeds of two shafts, as the input shaft and output shaft of a vehicle or other machine. It can be varied continuously within a given range, providing an infinite number of possible ratios.
The CVT transmission allows the driver or a computer to select the relationship between the speed of the engine and the speed of the wheels within a continuous range. This can provide even better fuel economy if the engine constantly runs at a single speed. The transmission is theory, capable of a better user experience, without the rise and fall in speed of an engine and the jerk felt when changing gears poorly.
EVT Transmission:
The electric variable transmission (EVT) combines a transmission with an electric motor to provide the illusion of a single CVT. In the common implementation, a gasoline engine connected to a traditional transmission, which is in turn connected to an epicyclic gear system’s planet carrier. An electric motor/generator is connected to the central “sun” gear, which is normally in-driven in typical epicyclic systems.
In typical implementation, the gear ratio of the transmission and epicyclic system are set to the ratio of the common driving conditions, say highway speed for a car or city speeds for a bus. When the driver presses on the gas, the associated electronics interpret the pedal position and immediately set the gasoline engine to the RPM that provides the best gas mileage for that setting.