Noise and Vibration in Switched Reluctance Machines
Acoustic noise and vibration is the most well-known issue in Switched Reluctance Machine (SRM). Due to the salient pole construction of SRMs, when a phase is excited with current, the flux penetrates into the rotor, mostly in the radial direction, and generates radial forces. Mechanical components and connections also contribute to the noise production in an SRM. Encapsulated stators are extensively used in SRMs. The stator core and windings can be encapsulated together by an insulation material, which provides additional protection and enhanced heat dissipation. From structural and noise perspectives, the encapsulation also provides additional stiffness to the stator since it bonds the teeth and coils together to form a closed ring. When the stator of an SRM is subjected to electromagnetic forces, the structure vibrates. The pressure and shear stresses caused by electromagnetic forces is called the force density, and for rotating machines, they are expressed with radial and tangential force densities.