A planetary gearbox refers to a gear system where a number of ‘planet’ gears rotate around a central ‘sun’ gear. Typically, a planet carrier is driven by the input torque which rotates the planets around a fixed outer ring (sometimes known as the annulus). Therefore drives the sun gear which then supplies the output torque. Nevertheless there are types of the other combinations, such as the sun gear being fixed and the ring providing output torque.
The main benefit of planetary gearboxes are their high power transmission efficiencies. Typicially this could be around simply 3% per stage. Additional to this, the high effiency can be delivered regardless of 
the compact design giving a large torque to size/weight ratio. A few of this is thanks to the load sharing that occurs over the multiple planet gears.
A planetary gearbox refers to a gear system where one or more ‘planet’ gears rotate around a central ‘sun’ equipment. Typically, a world carrier is powered by the insight torque which rotates the planets around a set outer ring (sometimes known as the annulus). This in turn drives sunlight gear which then provides the output torque. However there are examples of the additional combinations, like the sun gear being set and the ring providing output torque.
The main advantage of planetary gearboxes are their high power transmission efficiencies. Typicially this is often around simply 3% per stage. Further to the, the high effiency is definitely delivered despite the compact design giving a big torque to size/weight ratio. Some of this is thanks to the load sharing that occurs across the multiple planet gears.
Reliable Small Planetary Gearbox
EP Motor’s little planetary gearbox is available in 7 different sizes with diameters of 16mm, 22mm, 26mm, 28mm, 32mm, 36mm, and 45mm, each consisting with mono and multi-phases, and the gear ratios range from 3.3:1 ~ 1500:1.
Small Planetary Gearbox is a trend that is slowly increasing.