Planetary gear systems are primarily used for one or more of the following reasons:
- Reverse Motion
- Transmit more torque than one gear set will allow
- High reduction rates
- Use with other sets for multiple speeds
- Input and output need to be coaxial
Using a planetary gear system in a cordless helps to decrease speed / increase torque all while keeping the shafts coaxial. It also has a function that allows the ring gear to slip when the torque exceeds the desired limit.