Dual Planetary Gearbox for Variable Speed Drive
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Solution Overview
Problem
Existing drive arrangements for machines requiring variably adjustable rotational speed, such as compressors or pumps, are expensive due to the need for high-power medium-voltage frequency converters or hydraulically/electrically driven speed modulation systems, which are performance-limited by large internal gear diameters causing impermissible tangential loads.
Innovation Solution
A gearbox with two planet gear sets, where the first is coupled to a drive unit and the second to the machine, using a planet carrier driven by a second drive unit, allowing for variably adjustable rotational speed with simple and cost-effective elements, utilizing a low-voltage motor with an inverter for the second drive unit, which generates torque by the difference between drive and output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional speed modulation systems with large internal gears are used, then high power transmission is achieved, but tangential loads become impermissibly high and costs increase
Solution Approach 1:
The transmission system is segmented into two separate planet gear sets (first planet gear set for high-speed low-torque transmission, second planet gear set for low-speed high-torque modulation) instead of using a single large internal gear system. This segmentation allows each gear set to operate within optimal load parameters, avoiding impermissible tangential loads while maintaining high power transmission capability
Solution Approach 2:
The second planet gear set is nested within the first planet gear set, with both gear sets sharing common planet shafts and a unified planet carrier. This nested configuration allows compact arrangement of multiple transmission stages, enabling high power transmission through series connection of gear sets while keeping individual gear dimensions within acceptable load limits
2Adaptability or versatility
If medium-voltage frequency converters are used for variable speed control, then rotational speed adjustability is achieved, but system cost and complexity increase
Solution Approach 1:
The patent replaces expensive medium-voltage frequency converters with a mechanical speed modulation system using two planet gear sets. The variable speed control is achieved through mechanical means (engaging/disengaging the second drive unit on the planet carrier) rather than electronic conversion, significantly reducing system cost and complexity while maintaining rotational speed adjustability in the 4000-15000 rpm range
Solution Approach 2:
The system uses a dynamically configurable planetary gear arrangement where the second drive unit can be engaged or disengaged from the planet carrier to switch between fixed-ratio and variable-speed operation modes. This dynamic configuration allows simple mechanical implementation of variable speed control without complex electronic systems
Data Source
AI summary
A gearbox for a drive arrangement of a machine for driving the machine with variably adjustable rotational speed, with a first planet gear set, to which a first drive unit can be coupled and a second planet gear set, to which the machine can be coupled. The first planet gear set and the second planet gear set each comprise planet gears arranged on at least two common planet shafts which are mounted in a planet carrier. The planet carrier is rotatably mounted in a gearbox housing and can be driven by a second drive unit.