Induction motors, particularly small ones, are inefficient. Compared to the BLDC (or permanent magnet synchronous) motors more normally seen on these pages they have extra losses for 2 reasons, 1) the input power is also used to create the magnetic field, and 2) losses due to slip.
The main problem with this inefficiency is that the heat losses have to be dissipated. Look at an industrial induction motor, what you see is a big, fan cooled, aluminium heatsink. With an induction motor hidden inside it.....
The plus side for an induction machine in a traction application is that you effectively get electronic gearing built in. The machine output is constant torque (limited by magnetic circuit saturation and stator current capability) up to a base speed, and a reasonable approximation of constant power for a factor of 3 or 4 speed up over that, running with fixed maximum voltage in "field weakening" operation. So in a car you'd have a base speed equivalent to 1st gear in an ICE car & use field weakening to go faster up to top speed. No mechanical gears, like the tesla. For an induction machine, controlling field weakening operation is dead easy, a no- brainer. For a BLDC it's really quite tricky, unforgiving, hard to make safe and inefficient (because you now need to use input power to oppose the permanent magnet.....)
