Simplicity and reliability. The rotor is completely inert (no windings).

The big drawback has historically been "torque ripple". However, with modern high-speed power electronics, the current to the windings can be modulated to counteract this.

Full torque at 0 RPM. An SR machine combined with efficient backlash-free reducing gearing (torque amplification) may be able to deliver the reliability and torque density to replace frictional brakes. The "holy grail" of a combined traction motor and braking system may be within reach.

Thank you very much. Exactly what I wanted to know. But, just a doubt, even Induction motors offer full torque at 0 RPM, right? Please correct me if I'm wrong, because that's what a reviewer said while comparing a BMW and the Tesla Model S. Thanks!

Depending on the control system, yes. If you run an induction motor off a fixed-frequency supply, it produces very little torque until it is spinning near it's synchronous speed (typically 3600 RPM, but depends on the supply frequency and pole multiplicity). That's why, for example, bench grinders can take forever to come up to speed.

But modern control systems (which, I might add, are still much simpler than those for switched reluctance motors) can achieve full torque from a standstill (basically by bringing the synchronous speed to near zero).

Thank you very much!

Induction motors are not as power efficient as permanent magnet (PM) motors. Induction motors also weigh more compared to an equivalent PM motor and have more torque at lower RPMs. The reason induction motors are used is that they are cheaper than PM motors due to only using materials like aluminum and copper. PM motors use rare earth metals which are pricey and not great for us since China currently controls most of the world's production supplies.

For more detail read this article: http://electronicdesign.com/article/analog-and-mixed-signal/...

Thank you! That link is very informative.

Induction motors are good for some things, bad for others

It has all to do with speed x torque (x power) behaviour, and how it's controlled.

To change the speed on an induction motor is complicated, as opposed to changing the speed in a DC motor, where you just change voltage supplied

IIRC, Induction motors are great, but they have one major fault, without some complex circuitry, they can't be instantly switched on/off. Although a polyphase induction motor should not have that problem.

They are not as good as permanent magnet motors except on price/material availability.

See this article: http://electronicdesign.com/article/analog-and-mixed-signal/...

Induction motors used in vehicles are basically always three-phase machines driven by a variable-frequency inverter.

Full rated torque at 0 rpm.