This paper describes a mathematical approach for modeling and analyzing the broken magnet defects in a PMSG used for Marine Current Turbine (MCT). The modeling of magnet defects is investigated by using the Magnetic Equivalent Circuit (MEC) method. The MEC is founded on the linear modeling of the PMSG. Owing to the flexibility of this technique, the stator electromotive force (EMF) under faulty conditions can be calculated. The simulation results show that the MCT power generation and dynamic performances are highly degraded due to the fault.