the winding may be star or delta connected with the ends of the three windings terminated in the terminal box where 3-phase A.C. supply will be connected. The rotor construction can either be squirrel cage or wound rotor, but wound rotors can be expensive to manufacture hence they are hardly used in industrial applications.

Figure 4: 3 Phase Induction Motor
For a given power rating, the volume and therefore weight of an electric motor are proportionately reduced. This combined with the desire to reduce unsprung mass on the vehicle suspension dictates using a high-speed motor, coupled to the rear wheel via some mechanical reduction gearing [7]. The UoN racing electric motorbike uses a 3 phase GVM Parker Hannafin permanent magnet motor which can reach speeds of up to 10,500Rpm as shown in figure 1 [9]. Other motor models could have been chosen but the GVM motors from Parker are specifically dedicated for Mobile applications and specially designed for rugged atmospheres and harsh environments for traction, pump, auxiliaries, and steering. These motors are brushless synchronous servomotors, with permanent magnets which are made of rare earth magnets allowing high-temperature operation, water or oil cooling system and a resolver/encoder speed sensor. The water cooling increases the torque density allowing a silent operation [9].

This motor is preferred due to features such as high efficiency due to no current in the rotor hence losses in the rotor are very low due to the absence of brushes, commuters or slip rings, high dynamic performances, high power density, wide speed range as speed control is easy and efficient, high precision, high motion quality, Low inertia, compact dimensions & robustness, large set of options & customization possibilities such as a wide variety of applications of high speed/power to low speed/power, can be used either as motor or generator and operating voltages available from 24 to 800 VDC [9].
Conclusion