Electric motors have a wide variety of practical industrial applications. From the handheld electric drill to the big conveyor belts at manufacturing plants, electric motors are there to aid machines in various uses. To increase the versatility of an electric motor, you may use a gearbox to reduce or increase the speed of rotation, as well as to vary the torque output depending on the load requirements.
What Is a Planetary Gearbox?
As its name implies, the planetary gearbox arrangement resembles the planetary movement of the solar system. These are the following parts:
- The central gear, commonly known as the “sun” gear
- The gears which travel around the central gear, known as the “planet” gears
- The ring carrier, which holds the planet gears together
- The ring gear, which is an internal gear with its inside teeth meshing with the planet gears
The main functions of a planetary gearbox are as follows:
- To transmit power from a driving motor to a driven load
- To be able to reduce or increase the speed of a machine
- To be able to reduce or increase the machine’s torque output
All electric motors rotate very fast. You need to translate that fast rotation into something functional. Take the case of such machines as escalators, conveyor belts, elevators, and cranes. With all these, you need high torque because of the heavy loads these machines carry and transport or lift. However, you also need the torque at a very low speed. The planetary gearbox helps reduce the speed of the electric motors to suit the application.
As opposed to a conventional gearbox wherein you pick among various pairs of gears to engage with different ratios in order to achieve your desired speed, the desired speed in a planetary gearbox is attained by selecting the specific gears to be locked and the gears to be rotated. This is done by locking or freeing any of the planetary gearbox parts, such as the sun gear, planet gears, or the ring gear.
Depending on which parts you lock with hydraulic pressure, the output shaft will output anything from low speed to high speed. The output shaft can even reverse rotation. To gain more gear reduction, the designer can install multiple planetary gearboxes in a series to produce more possible combinations of rotation speeds.
To survey your options for high-quality planetary gearboxes that will match your needs, you may check this PJM page.
How Does a Planetary Gearbox Work?
Planetary gearboxes are quite popular. Here are some ways that they work:
- For big changes in gear ratio, a planetary gearbox can achieve a bigger reduction in speed in a much smaller package. This means that for applications with a wide variety of speeds required, you can deliver that range of speeds in a relatively compact setup.
- Planetary gearboxes are capable of quicker speed changes. Compared to conventional parallel shaft gearboxes, a planetary gearbox can shift speeds much faster. This is due to its design wherein the shafts and gears are always in contact with one another and are synchronized. For conventional gearboxes, the unused gears rotate freely or “float” on the shaft. When a certain pair is to be used again, its speeds have to be synchronized first with the shafts before it can transmit power. Planetary gearboxes respond quickly to speed changes.
- Planetary gearboxes can change ratios while under load. Unlike conventional gearboxes, planetary gearboxes can switch from different gear ratios while power is being transmitted. This means that there is a much shorter time delay and minimized power loss during the shifting of speeds.
- The load in planetary gearboxes is more evenly distributed to more components. In conventional gears, the torque is usually purely handled by one pair of gears. For planetary gearboxes, the torque is distributed among the different gears depending on their current use. This means that for the same size of gears as those found in conventional gearboxes, a planetary gearbox can handle higher torque values.
- As opposed to conventional parallel shaft gearboxes, the planetary gearbox can have the input and output shafts in one line. The shafts are collinear. This type of arrangement means that the torque being transferred from the motor to the load is transmitted in a straight line, lessening the torsion (or turning) stresses on the assembly and case.
Conclusion
Whether for your business needs in a factory or your daily needs such as in transportation, planetary gearboxes are of great use. Learning about what planetary gearboxes are and how they function can give you a deeper appreciation of the indispensable role this mechanism plays in a variety of equipment with electric motors.
