Future electric motors build will be SR Motors.
The small-size SR motor was developed by Akira Chiba, professor at the Department of Electrical Engineering, Faculty of Science & Technology, Tokyo University of Science.
The prototyped SR motor has the same size as the 50kW synchronous motor equipped in the second-generation Toyota Prius. Curently all produced Electric cars are equipped with a synchronous motor whose rotor is embedded with a permanent magnet.
But as the permanent magnets are getting more and more pricey (the price has doubled or trippled) because of higher demand, the future of SR Motors is now imminent.
- Maximum torque of 403N·m
- Efficiency of 86%
- The torque density of the SR motor is 45N·m/L.
SR motors have a significant torque ripple, especially when operated in single-pulse voltage control mode. This is the price to pay for high efficiency. For many applications where the machine is operating at fairly high speeds, this is not a problem since the mechanical time-constant is far longer than the fast rates of change of instantaneous torque produced by the motor.
A four-phase 8/6 switched-reluctance motor is shown in cross section. In order to produce continuous shaft rotation, each of the four stator phases is energized and then de-energized in succession at specific positions of the rotor as illustrated.
There is some literature, if you want to get further….
Image source: here
Post source: Tech-On