Page - 111 - in Hybrid Electric Vehicles

propulsion. SynRM’s performance strongly depends on the saliency ratio, but increasing the saliency complicates the rotor construction and drastically increases the motor cost. Interesting results concerning the influence of the saliency ratio on the SynRM steady-state performances, mainly on power factor and efficiency, are given in Ref. [21], while the effect of rotor dimen- sions on d- and q-axis inductances in the case of a SynRM with flux barrier rotor is discussed in Ref. [22]. Thus, the number of rotor flux barrier for the SynRM recommended in the literature is four. Above this value, the technology of the rotor is too complicated, while for a value lower than 4, the value of the torque ripple is too high. Regarding the rotor construction, there are three main different types, given in Ref. [23], presented in Figure 5. • With salient rotor poles (see Figure 5a): require low technological effort and are obtained by removing the iron material from each rotor pole in the transversal region. • With axially laminated rotor (ALA) (see Figure 5b): the rotor core is made of axial steel sheets that are insulated from each other using electrically and magnetically insulation (passive material). • Transversally laminated anisotropic rotor (TLA) (see Figure 5c): the so-called ribs are ob- tained by punching and then the various rotor segments are connected to each other by these ribs. The SynRM has a larger torque density compared with that of IM. This comes from the absence of rotor cage and related losses. A different dynamic behaviour is expected from SynRM due to the specific relationships between currents and fluxes. Because SynRM does not have a traditional cage (especially used for starting), it is necessary to use the modern inverter tech- nology. Therefore, most of the literature on SynRM drives has concentrated mainly on the design and control of the machine with the goal of improving control, efficiency and torque production, drive flexibility and cost [24]. The main drawback of SynRM is related to structural behaviour at high speeds (over 10,000 rpm) because the specific geometry of the rotor involves thin layers of steel and large cut-off areas. Figure 5. Rotor topologies for a SynRM: (a) simple salient pole, (b) axially laminated anisotropy rotor, and (c) transversally laminated anisotropic rotor. Source: [23]. Performance Analysis of an Integrated Starter-Alternator-Booster for Hybrid Electric Vehicles http://dx.doi.org/10.5772/intechopen.68861 111