Loss Analysis of a Free-Piston Transverse-Flux Linear Generator under Reciprocating Variable Speed Motion

The Free-Piston linear generators work in reciprocating variable-speed motion, but they are often simplified and equivalent to uniform motion, which leads to inaccurate losses calculation of the generator, and thus affects the calculation accuracy of efficiency. The transverse-flux linear generator (TFLG) is very suitable for free-piston power generation due to its outstanding performance. However, its magnetic circuit is relatively complex and thus its loss calculation is quite special. Therefore, the loss characteristics of the free-piston transverse-flux linear generator (FPTFLG) require in-depth analysis. Firstly, this paper delves into the effects of variable speed motion on stator core loss, copper loss, and permanent magnet loss. Then, the precise transient loss models have been proposed to accurately evaluate the loss changes of linear machines under reciprocating variable speed conditions. Finally, compared to uniform motion, the impact of electromagnetic performance such as efficiency and output power of FPTFLG under reciprocating variable speed motion is thoroughly analyzed.