Variable Speed Planetary Gears for High Power Application
Electric driven centrifugal compressor units are well established in the US pipeline system. Synchronous electric motor drives and variable speed planetary gears have been in use in the pipeline industry and today pipelines are going to be installed using turbo-compression for the first choice. New planned large scale pipelines reflect the growing demand of natural gas in the American economy in order to use clean fuel. Further new emission regulations make the use of gas turbines less efficient and expensive. High reliability, up-to-date efficiency, practically no emissions and low capital investment recommend electric driven compressor stations. The market of today requires unspared equipment with a power requirement of over 40,000 HP per station. This paper describes the latest developments in this power range, component design and starting and operation characteristics of the variable speed planetary gear. The operating range (torque vs. speed) is shown based on examples and its limits are explained. The extension of the product range towards higher power rating is not the only design aspect. Also, accessibility and maintainability issues have been considered to improve the operators satisfaction and reduce costly investments in infrastructure of compressor stations, for instance cranage capacity. Some recent examples of different oil and gas applications in the US are presented.