Subsea Permanent Magnet Motor with Damper winding

Abstract

Permanent Magnet (PM) machines can have difficulties dealing with unstable loads, which in worst case can make the machine to step-out of synchronous speed. This problem can be avoided by equipping the rotor with damper windings. During load variation the damper winding will induce a torque to dampen the impact of the load variation. To investigate the effects from using damper windings a numerical model of a PM machine was developed and studied in this thesis. The model is intended to operate with regards to load torque and the stator field. The stator configuration which was used in this thesis is very complex, which resulted in a lot of trial and error. Due to the complexity of the stator meant it had to be applied with a current density, which means that the voltage over the phases was not taken into account during the simulations. This simplification appears to have created an unnatural damping factor in the simulations.Simulations show that a high-conductive damper winding performs faster during load variations then a low conductive damper winding. The reason for this is that a low resistance will induce a high torque at low slip. The size of the windings also affects the performance but these are small and difficult to notice. Simulations show that the size of the damper winding should be between 5-10% of the size of the stator winding.