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 What Is a Planetary Gearbox, and How Does It Works?

What Is a Planetary Gearbox, and How Does It Works?


Planetary gearboxes are one of the most common drive control devices. It is an essential component in automatic transmission applications for automobiles. In industry, a planetary gearbox is a type of gearbox.so what is a planetary gearbox and how does it works? in which the output and input share the same center of rotation. This indicates that the input and output shafts are aligned . and that the center of the input gear rotates around the center of the output section. Before we can comprehend how a planetary gearbox operates. we must first comprehend what a planetary gearbox is. so allow KONIC to provide a thorough explanation.

What is a Planetary Gearbox?

Planetary gearbox is a type of widely used speed reduction equipment. For the purpose of Planetary gearboxes are primarily used to reduce speed. in order to increase torque and reduce the load / motor rotation inertia ratio.

The planetary gearbox adopts in volute planetary gear transmission. And rational use of internal and external meshing,power shunt. At the same time, the box body adopts ductile iron. greatly improving the steel and vibration resistance of the box. And gears are carbonized quenching treatment. In order to get a high hard wear-resistant surface. gears after heat treatment all grinding teeth, so reducing the noise. Obviously improve the efficiency and service life of the machine. usually planetary gearbox planetary transmission stages have 2 and 3. which is the most This is the most common number of stages.

How Does a Planetary Gearbox Works?

Origin of Planetary Gearbox

Planetary gearboxes are so named. because the gears move in a similar pattern to the planets of the universe. We see a satellite (ring) gear, a sun (sun) gear and two or more planetary gears in the planetary gearbox. The sun gear operates normally and turns the planetary gears bolted to the planetary frame to form the output shaft. The satellite gears have a constant position relative to the external components. This looks like our planetary solar arrangement, which is where the term comes from.

Internal Structure of Planetary Gearbox

The main transmission structure of planetary gearbox is: planetary wheel, sun wheel, inner gear ring, drive motor and transmission shaft. The planetary gearbox divided into three sections from the appearance: input section, reduction section and output section.


industrial gearbox assembly

Input section:

The input section refers to the end connected with the motor. Including input shaft hole, input flange

Reduction section:

The reduction section refers to the core section of the gearbox. which looks like a box from the outside. but actually contains many core components. such as planetary gears, sun gears and internal gear rings.

Output section:

output section refers to the end connected to the equipment. including the output shaft, output flange.

As mentioned before, the planetary gearbox has a “sun” gear in the middle – also called the center gear. This is always the input section. On the outside, there are two or more “planetary” components – or external gears. Around the planetary components, there is a ring component that incorporates the formation. The planetary gears connected by brackets. which in turn connected to the output shaft.

Working principle of planetary gearbox

The planetary gearbox has a relatively simple design and consists of a central sun wheel. an outer ring (tooth side inward also known as the inner gear), a planetary carrier and a planetary gear. The input power of the sun gear causes rotation. There is a standard for the meshing of the planetary gear with the sun wheel. and as the sun wheel rotates on this basis, the planetary gear also rotates on its axis. The planetary gear is also proportional to a fixed ring section. causing the planetary section to rotate around the sun gear. The planetary carrier maintains the basic shape of the planetary gears and sets their clearance. It rotates together with the planetary parts and contains the output shaft.


The principle of planetary gearbox is a power transmission mechanism. that uses the speed converter of gears to decelerate the number of revolutions of the motor. to the desired number of revolutions and to obtain a larger torque. The gears with fewer teeth on the drive shaft of the planetary gearbox mesh. with the larger gears on the output shaft to achieve the deceleration. In order to achieve the desired reduction effect. ordinary reducers have several pairs of gears of the same principle meshing together. the ratio of the number of teeth of the large and small gears, is the transmission ratio.

What is the advantages of planetary gearbox?

Small volume, light weight, high load capacity, long service life. smooth operation, low noise, high output torque, high speed ratio. high efficiency, and safe performance are characteristics of this product. In conjunction with a power shunt, multi-tooth meshing possesses distinctive qualities. The transmission efficiency of planetary gearboxes is typically greater than 90%. and can exceed 95%, making them a popular choice.

High load-bearing:

The planetary gearbox with planetary structure achieves self-adaptation, so that each pair of meshing pairs participating in the engagement can achieve equal load, so that the average load on a pair of meshing pairs is reduced, thus improving its load-bearing capacity and impact resistance.

High precision, heavy load:

Need high precision positioning and heavy load would selected planetary gearbox. in some industries such as robotics, medical military and other industries. their machinery and equipment in the operation of a common characteristic . that is the torque required more than the servo motor itself has the torque. So through the planetary gearbox can be a good solution to this problem.

High efficiency:

Planetary gearboxes provide higher efficiency due to their design. and internal layout losses are minimized during their operation. Planetary gearboxes used together with servo motors. that can serve the purpose of boosting torque. therefore boosting the speed of servo motors and making the power density of the whole servo system twice as high. which can well improve the operational efficiency of the whole machinery and equipment.

Increased torque transmission:

High torque density, several planets share the load rather than one gear. the more planets, the more load shared, and keep more uniformly.


Its mechanism contained in a cylindrical gearbox . that installed almost anywhere. thanks to its compact dimensions and low weight, a 50% reduction in diameter. and the same torque output as an equivalent parallel shaft gear.

Low noise:

Low noise and smooth transmission. The volume of the column pin ring is small. and swivel arm bearings are chosen . based on the strength requirements after achieving smooth inertia forces. resulting in smooth and low-noise transmission.

Applications of planetary gearboxes

Planetary gearboxes used in a wide range of applications. initially in cooperation with electric motors. in addition to micro gear motors, in office automation, smart home, production automation. medical equipment, financial machinery and other fields. Such as automatic curtains, intelligent toilets, lifting systems. banknote machines, advertising light boxes and other industries.

  • Automation equipment
  • Waste water treatment
  • Dredgers
  • Chemical industry
  • Metal working mills
  • Conveyors
  • Frequency converters
  • Reciprocating compressors
  • Cranes
  • Cooling towers
  • Paper machines
  • Cable ways
  • Cement industry
  • Wood industry
  • Plastic industry
  • Rubber industry
  • Sand roller
  • Hammer crusher

How to choosing planetary gearbox?

Here are the steps you need to take to choose a planetary gearbox. Before choosing a planetary gearbox, the following things should known:

1.Torque to be transmitted (output torque)
2. Motor Power (kW)
2. Input speed (RPM)
3. Output speed (RPM)
4. Operating condition (i.e. No of Start-ups per hour and it subject to impacts
5. Ambient temperature (°C)
6. Radial load on output and input shaft thrust load if any.


The following are selection examples

Prime mover 

Motor Power : 90kW

Motor Speed: n1=1000r/min

Max. starting toque: 2000N.m

(This value is usually provided by users. f not available, it is routine to calculate by 1.6 times of nominal torque of electric motor.)

Driven machine

Name : bucket conveyor

Speed: 12.5r/min

Output torque: 68000N·m


Starts per hour: >3 times

Operating cycle per hour: 60%

Ambient temperature: 20℃

Place of installation: in the open

Altitude: below 1000m

Gear Unit

Parallel input shafts, solid output shaft with parallel keys, input shaft facing downwards, mounting position

Selection steps:
Determination of gearbox type:
    • Calculation of the ratio:i=n1/n2=1000/12.5=80
    •  Selection of gearbox type:P2SB..-B53 selected(as per the ratio, input and output shafts).
Determination of gearbox size:

Calculation of the nominal power of gearbox:

P1=T2·n1/(9550·i·n )

In the table of transmission capacity on P5,n =0.93

P1=T2.n1/(9550·i·n)=68000×1000/(9550×80 x0.93)=95.7kW

P1N2P1 xf1 x f2 x=95.7 x1.5x1x1=143.6kW

See P7,f1=1.5,and P5 f2=1 P8,SF=1

P1N P1 xf1 x f2=95.7 x 1.511=143.6kW

Selected from the table of transmission capacity: P2SB14-80-B53,

where P1N=149kW iex=78.8


3.33x 95.7=318.681>P1N, satisfied.

2.3 Check of peak torque


=2000 x1000 x0.5/9550=104.71kW,satisfied

Check of thermal capacity

Nominal power utilization=P1/P1N=95.7/149-0.642=64.2%

So f14=0.9 ft=1.16

PG1 x ft x f14=94 x 1.16 x 0.9=100.32kW>P1

So no auxiliary cooling device is needed

Lubrication: Dip

The type selected: P2SB14-80-B53

Which Planetary Gearbox that we Require?

The gearing ratio and size of a planetary gearbox determined by the outcome. It is critical to achieve a balance between efficiency, size, cost, and performance. Famous builders use a consultative approach to modeling. we begin each project by developing deep learning of the specific case. the torque, speeds, and machine performance.

KONIC also use their knowledge and experience to determine. and provide a reliable and cost-effective planetary gearbox method. Every gearbox we supply will provide years of trouble-free service. The combination of continuous innovation and engineering excellence. keeps us at the forefront of planetary gearbox technology.

What Should You Keep in Mind When Buying A Planetary Gearbox?

What are the acquisition considerations for a planetary gearbox? This is a difficult question to answer. as the answer depends heavily on the precise application of the gearbox. In addition to the primary features (e.g., backlash, torque, and ratio). secondary (e.g., noise level, corrosion resistance, and construction). and tertiary (e.g., price, delivery time, service, and global availability) features .

You can contact the constructors for all your inquiries. we will respond immediately, always on the same day. with a personalized response and/or comprehensive proposal. With this method, you never need to concerned about a delay. as they deliver every planetary gearbox faster than anyone else.

For more information on the use and maintenance of lubricants for planetary gearboxes, please read

The Ultimate Guide on the Use of industrial gearbox oil painting

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