ARMATURE SLOT RIEPPLE LOSS IN ROTOR METALLIC SLEEVES OF SYNCHRONOUS MACHINES USING FINITE ELEMENTS

Eddy current loss in the rotor metallic sleeves of high-speed synchronous machines due to armature slot ripple is known to make a significant portion of the no-load losses in some machines. This paper describes a method for loss calculation in the rotor sleeves of such machines using finite elements. The method suggested here offers several advantages over the standard industry practice [1]. It takes into account local tooth saturation and makes no assumption on the wave from shape. The paper shows how the use of finite element method can provide insight into the slot ripple loss mechanism by computationally deriving the ripple waveform and studying its major spikes and notches. This study can pinpoint the major cause of unusually high rotor sleeve losses in some machines and help to alleviate the problem at the design stage.