Why are Motors Used With Planetary Gearboxes?

Motors have power requirements in terms of speed and torque ratios. If the load requires high torque at low speed, it is obviously not economical to use a large motor to achieve this torque, and the system efficiency is extremely low. In this case, some kind of gear can be introduced between the motor and the load, which is a better solution. Gears allow the motor to adapt to the load, whether in terms of speed, torque or inertia. The transmission system is provided based on the motor gearbox solution. The gear system is composed of metal or plastic gears, the motor and gearbox combination will bring higher efficiency, which can be said to be an economical solution. Gear motors can provide torque at low speeds.

Planetary Gearboxes: Higher torque ratings, and very high reduction ratios per gear train. It uses high-quality synthetic materials, and the metal planetary gearbox is compact in design, it has excellent performance and service life.

High-Speed Planetary Gearbox: This high-performance product family is designed for use with BLDC motors with iron core coils, the gearbox can withstand input speeds ranging from 10,000 to 70,000 rpm, and can withstand output speeds of about 1,000 multiple times the rpm, which allows the motor and gearbox system to be controlled to an extremely small size and also to provide extremely high speed or torque values. P

Principle of planetary gearbox

The pinion S (= sun) with “S” teeth drives the planets P with “P” teeth (3 or 4 per gear train) and is fixed to the spur and planet carrier. A = Fixed ring gear with “a” teeth, the reduction ratio of each gear train is i = (a:s)+1. 3 or 4 transmission points per gear train, the gear train has a high reduction ratio, high friction can transmit high torque, input and output are the same rotation direction, less backlash. With fewer gear trains for a given reduction ratio, each gear train is approximately 85% efficient. Excellent performance and compact gear head, the load always rotates in the same direction as the motor for any number of gear trains, and the motor reverses quickly with less shock.

How to choose a gearbox?

In addition to the dynamic output torque, the following factors should be considered when selecting a gearbox to work with the motor:

  • The direction of rotation: It indicates the direction of the output shaft relative to the motor (= or ≠). In a planetary gearbox, the direction of input and output is always the same regardless of the number of gear trains.
  • Efficiency: It mainly depends on the number of gear trains. It is an average measurement at an ambient temperature of 20 to 25°C, the value is lower for new gearboxes, but will reach normal values after a period of operation.
  • Maximum static torque: This is the maximum torque that the stall can withstand, beyond this limit, the gearbox may be damaged.
  • Maximum recommended input speed: It has a large impact on the noise level and service life of the gearbox and should be considered when selecting a reduction ratio for different applications.
  • Backlash: This is the angle at which the output shaft of the gearbox is free to rotate when the input is blocked. Its main determinants include the necessary gear play to avoid gear jamming, the shaft play and the elastic deformation of the gear teeth and shaft under load. Since it is load-dependent, two values for torque with and without load can be derived. In fact, the backlash of the gear train appears on the output shaft as the reduction ratio decreases. In contrast, the backlash of the output shaft appears on the input shaft as the reduction ratio increases. For a 100:1 ratio, 1 degree of backlash represents 100 degrees of rotation at the input, and each time the motor reverses, the output won’t start to rotate until this 100 degrees of rotation is captured.

Leave a Comment

Your email address will not be published. Required fields are marked *