Longitudinal End Effects in a Linear Wave Power Generator

Even though the magnetic circuit of a linear electric machine is very similar to a rotating electric machine, they diverge in one fundamental property. The linear generator is open in both ends, i.e., the magnetic circuit is non-symmetric. This paper investigates and discusses the drawbacks of this non-symmetric design in a linear permanent magnet generator, installed in a wave energy conversion system. A two-dimensional geometry has been utilized for the numerical calculations in a finite element method simulation tool. The results present an increased cogging force and significant core losses in the translator as consequences of the longitudinal ends in the machine.

Numerical Modeling of Dynamic Processes of the Reciprocating Reversible Electrical Machine

Now rotational electrical machines are used mainly for the implementation a reciprocating motion of working mechanisms and also as the electric generators powered by internal combustion engines. It is achieved by means of the kinematic transfers complicating a design and reducing the drive efficiency. The use of linear reciprocating electric machines allows to eliminate these defects. It should be noted that the most effective ones are the cylindrical designs of reciprocating electric machines with permanent magnets, whose efficiency reaches 93 – 95%. However, the rarity and lack of a mass production of this machine type and special recommendations for their design causes the need of research, directed on search of optimum constructive decisions. The article describes the types of linear electrical machines and summarizes the results of numerical modeling of dynamic characteristics for the three versions of the reciprocating cylindrical machine with permanent magnets of 10 kW with the oscillation frequency of the translator 20 Hz and the length of operating cycle of 120 mm. The most effective design parameters of linear electric machine were determined on the basis of its specific characteristics and analysis of the EMF graphics shape, appearing on the stator windings in the generator mode.