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Alternators usually have a solid pulley to connect it to the Front-End Accessory Drive (FEAD) system. Current stringent emissions regulations and fuel economy push for new alternatives to meet goals such as, for instance, reduced idle speed and engine downsizing. However, achieving these goals could ultimately generate NVH issues, such as belt slip chirp noise, or reduced accessory-drive support bearing life due to the high vibration levels in the FEAD. Furthermore, increased demand for on-board electric/electronics systems are requiring the use of larger alternators, with bigger inertia, becoming an additional source of vibration.

Alternators used to have a solid pulley to connect it to the Front-End Accessory Drive (FEAD) system. Lately, new breakthrough designs have been developed for some applications, as the Overrunning Alternator Pulley (OAP) and the Overrunning Alternator Decoupler (OAD), with the aim to detach the alternator from the FEAD during high speed transients and to reduce the transmission of torsional vibrations from the internal combustion engine to the engine accessories, respectively. The downsizing of the internal combustion engine and its reduced idle speed to improve fuel economy and emissions led to belt slip or creep, increased NVH issues as chirpy noise or bearing reduced life due to the high vibration levels. Besides of that the increased demand for electric/electronics on-board systems led to the use of larger alternators, with bigger inertia, generating even higher vibration levels.