Integrated Starter-Alternator with Sensorless Ringed-Pole PM Synchronous Motor Drive

The so-called integrated starter-alternator (ISA) is a high-efficiency electrical machine that is connected to an internal combustion engine obtaining mild hybrid electric vehicles. The ISA has a twofold task: starting up the engine and generating electrical energy to be stored into a battery. This paper is focused on the first task. Two different motors are investigated: an external rotor surface permanent magnet (SPM) machine and an interior permanent magnet (IPM) machine. For drive control, both motors require knowledge of their rotor position; then, a sensorless technique based on the high-frequency (HF) voltage injection for rotor position detection has been implemented. In order to create an HF anisotropy in the SPM rotor configuration, a ringed-pole solution has been adopted. Experimental tests have highlighted that the first machine has a clear capability of starting up the engine with good speed and position estimation in spite of the particular nonconstant load torque. As regard the IPM machine, the sensorless engine startup appears not possible because the anisotropy disappears at a high current level due to saturation effects.