ABSTRACT
In conventional vehicles, the traction power is supplied by the internal combustion engine. In order to provide power to the vehicle electrical loads, a low-voltage system is utilized, which includes a belt-driven alternator, low-voltage battery, and various electrical loads. When the engine is running, it provides torque to the alternator, which then provides electrical energy to the 12 V battery. In conventional vehicles, claw-pole synchronous generators are utilized, due to their low-cost structure and reliable operation. However, claw-pole alternators usually have low efciency because of the high leakage ux. Depending on the charging current of the low-voltage battery and the load requirements in the vehicle electrical system, the eld current of the claw-pole alternator is controlled by a regulator to keep the system voltage constant. In light-duty vehicles, battery voltage is usually 12 V, and when the vehicle is running, system voltage is approximately 13.5 V in summer time and 14.5 V in winter time. With the engine stopped, only low-voltage battery supplies power to the electrical loads. The battery also behaves like a buffer in the electrical systems and stores energy.
