What’s the Role of a Planetary Gear Set?

The vehicle gearbox contains something called planetary gear sets which provide different gear ratios.

A planetary gear set consists of a sun gear and planet gears which rotate around the central sun gear, like our solar system. A planet carrier gear connects the planet gears with a ring gear that meshes them. The planetary gear set prevents certain components from moving when using clutches and brakes. This alters the input and the output of the system that changes the overall gear ratio.

Depending on which component is fixed it will determine the final gear ratio. If a ring gear is stationary or fixed, the ratio will be shorter than if the sun gear is fixed or stationary.