39 Electric Motors The inductance components of the SynRM rotor change depending on the load because of saturation eff ects. Therefore the individual inductances L d and L q depend on I d and I q current (L d (I d ,I q ) and L q (I d ,I q )). If this is taken into account, very high energy effi ciency operation of the motor is possible. Over a certain power range the part-load effi ciency has advantages against other concepts. For decades, asynchronous motors were state of the art, while other technologies were only used in niches. The trend towards more energy effi cient motors and the opportunities provided by FC’s has resulted in innovative technologies like the improved SynRM.
More improvements and optimisations are in development. 1.4.7 Switched Reluctance Motor (SRM) Construction of the stator is very similar to that of DC motors as concentric windings are used. This can result in a compact housing. The rotor lamination design has a very clear shape with low inertia where the number of poles can easily be counted. While on two pole motors the rotor poles are aligned with the stator poles, the pole ratio is typically diff erent. This principle is also applied on other motor types but it is very obvious on switched reluctance motors. 6/4 pole 8/6 pole Fig.
1.33 Switched reluctance motor confi guration examples To run the motor a suitable controller is required, which energises the stator coils in a sophisticated way. The phases are energised one after the other. When the coils of a phase are supplied with a voltage, a fl ux is established through the stator poles and the rotor, which results in rotor movement. After the rotor has started moving the voltage will be switched to the next phase and so on.