Planetary gear (also called epicyclic
gear) is a kind of a gear arrangement usually used for applications
where dealing with high gear ratio and small dimensions is present.
Although there are many different types of planetary gear, the three
and four wheel types are the most common. Gearboxes that use a three
wheel design implement the three planetary gears in two different
stages. However, a three wheel design cannot make use of three
planetary gears since here, three wheels addresses the number of the
distinctive sizes not the number of the planetary wheels. One stage
can sometimes come to a ratio of ten and there are certain instances
when a higher ratio is required. When one needs to achieve a higher
ratio, they should pair two or more stages and this should be done in
an enclosure so that a gearbox with variable ratio and axis direction
of the rotation is created.
