Equivalent Lumped-Parameter Modeling of a Conductive Protective Shell in Permanent-Magnet Synchronous Generators

Abstract

The deployment of permanent-magnet synchronous generators (PMSGs) in harsh environments, such as floating wave energy converters and downhole geophysical systems, necessitates robust mechanical and chemical protection. Solid conductive shells are frequently employed to shield stator components from corrosive fluids and extreme pressures. However, these conductive enclosures induce significant eddy currents under time-varying magnetic fields, profoundly altering the machine's transient electromechanical dynamics. This paper proposes a generalized dynamic model of a PMSG with a conductive stator shell, formulated in the rotating d-q reference frame. To ensure computational efficiency without sacrificing physical fidelity, the distributed shielding effect is represented by an equivalent lumped-parameter, three-phase short-circuited winding. Analytical reduction of the model reveals that the shell substantially decreases the effective stator inductance during fast transients and accelerates the decay of aperiodic current components. Consequently, the stator circuit time constant is reduced, and three-phase short-circuit peak currents are limited by 15-40%, thereby mitigating the risk of irreversible permanent magnet demagnetization. Furthermore, a parametric analysis identifies an optimal shell resistance range that balances transient current suppression against steady-state eddy-current losses. The proposed modeling framework provides a computationally efficient tool for the design, transient analysis, and control synthesis of shielded PMSGs in renewable energy and subsurface applications.