A Pragmatic Approach for Comparative Analysis of Linear and Rotary Generators

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A Pragmatic Approach for Comparative Analysis of Linear and Rotary Generators


This paper identifies the need for consolidating analysis techniques for the purpose of designing linear electrical generation systems. Additionally, it identifies a need for concise system development tools that help designers make practical comparisons between linear and rotary machines.


The basic principles for converting mechanical energy to electrical energy have been known for over a century. It would seem that after this much time, advancements in electrical generation should have reached their limits; however, up to the late 1980’s and early 90’s the use of linear generators for the generation of electricity has not been seriously considered [1] [4].

Linear generators and motors are classified as linear motion electromagnetic systems (LMESs) [1]. LMESs that are used as electric generators function by directly utilizing the translational (back and forth or up and down) thrust from mechanical systems to generate electricity as opposed to the more conventional generation approach of rotational mechanical energy conversion.

For an engineer to determine the feasibility of using a linear electric generator in a system’s design many comparisons between rotary and linear machines must be made. Several points to consider when making this comparison include: practicality of using linear power generation for that particular system, cost to build and design, total system efficiency, role of modern day power electronics, type of driving force (linear or rotational) applied to the generator system, system power factor, force density and force ripple on the drive components, cost to maintain, and the system’s reliability. The relative weights of these considerations will vary from one system to the next. The motivation behind this question was the decision on whether to use a linear or rotary generator on a buoy driven, ocean wave electrical generator project [6]. During this decision process, many opinions and assumptions between these competing systems were made, but finding hard data that compared the two methods was not readily available. Taking the time to thoroughly evaluate the electrical and mechanical technical aspects of this choice (rotary vs. linear) conflicted with the tight scheduling requirements of the project. This situation forced the team to make a best approximation based on limited experience instead of a deliberate and thoroughly evaluated approach.


Electrical energy generation is being expanded by creative innovation, and linear generators are a large part of this trend.

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