Interesting facts about SET Planetary gear stage - Sustainable Energy Technologies

Well-known that SETCON gearbox consists of a differential planetary gear. The Planet carrier with three planets is connected to two Servo motors in order to adjust a variable output speed from 20% to 105%, with an overall efficiency of more than 99%. But how is it working?

  • The Planetary gear ensures the speed control at a Driven Machine (e.g., Pump or Compressor) and, additionally, regulate the torque in the entire drive train.
  • The planet carrier with three planets, is connected via additional gear stages with the two Servo motors operating at variable speeds with up to 2000 rpm, located on the top of the gearbox. By turning the planet carrier in the same direction than the sun gear (connected to the Driven Machine) the speed / power is increased, and the Servos add additional power to the system. The main power flow derives from the Main Motor (connected to the Ring gear) and is superimposed by the Servo power.
  • Additionally, the two Servos can “brake” the system with up to 20% of the system rated power by turning the planet carrier in the opposite direction of the sun gear. The generated energy (Servos work as generators) is fed back to the grid and is consumed by the Main Motor again. Unlike hydraulic systems, where this energy is converted into heat loss, the braking energy is used regeneratively. This results in very high system efficiencies in the partial load range. Watch Animation.
Sustainable Energy Technologies Planetary gear stage animation
  • Important advantages of Planetary gears are the up to 3 times increased torque capacity per-unit-volume (compared to spur gears). This allows a superior compactness of the device.
  • These units are well-known for the exceedingly long service life. Higher stability and resistance to damage of planetary gears is kept thanks to multiple larger contact surfaces and uniform weight distribution in comparison to other gear types.
  • Planetary gears are applied by humans for centuries. Under one of the theories, a similar device was used by Ancient Greeks inside the Antikythera mechanism in the 2nd-3rd centuries BC to calculate the motion of celestial bodies and dates of astronomical events. Later, in XI century Arabian engineer Ibn Khalaf al-Muradi mentioned planetary gears in his instruction on clock designs.