What are Planetary gears

A planetary or epicyclic gear is a system or gear train made up of one or more external gears or satellites that rotate on a sun gear or planet. Normally, the satellites are mounted on a mobile arm that also allows them to rotate in relation to the central gear. These systems can also incorporate an external ring gear or ring gear, which meshes with the planets. In simple worlds we can say that Planetary gears is a set of gears with the input shaft and output shaft aligned. A planetary gearbox is used to transfer the greatest torque in the most compact form (known as torque density)

Figure 2: Planetary gear set

planetary gear systems used:


Planetary gears are often used when space and weight are an issue. but a large amount of speed reduction and torque is needed. This requirement applies to a variety of industries, including tractors and construction equipment. where a large amount of torque is needed to drive the wheels. Other places you’ll find planetary gear sets include turbine engines, automatic transmissions, and even electric screwdrivers.

Working of planetary gears:

The two gears should have the same speeds at the interface. The speed of gear A should be same as that of gear B at their mating point.
A planetary gear set is comprised of an outer gear ring that’s called the ring gear. As they rotate inside of the ring gear, the planetary gears create pitch circles that can be formed into a gear train. that in turn, is hooked up to input and output shafts.

Figure 3: Gears A and B

  • The gear teeth will penetrate each other, which is an impossible condition. So that’s way the speed has to be the same.
  • Gears are mostly used in automobiles for power transmissions for havey load vahical.
  • Planetary gears in THS-II: The inner wheel or sun gear is connected to MG1, the wheels around that (planet gears) are not connected at all but their axles (carrier) is connected to petrol engine, the ring gear is connected to the wheels through
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