• Motors

    Motors serve many roles in today’s automobiles, especially in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Note: EVs include both fuel cell electric vehicles (FCVs) and battery electric vehicles (BEVs). In HEVs and EVs, motors may be used for vehicle propulsion, regenerative braking, air conditioning, power steering, internal combustion engine (ICE) cranking (starter), coolant and transmission fluid pumps, and fans. These motors may run off alternating current (AC) or direct current (DC) depending on their design and application. For example, electric air conditioning may use AC current while the electric power steering uses DC current. Advantages of electric motors are:

    • Instant and constant torque at any rpm  
    • Efficiency (76.4–80.2% from inverter to wheels, Source: SAE 2011-01-0887)  
    • Smoothness  
    • Quiet  
    • Reliability 
    • Simplicity 

    Motor Operation

    Motors convert chemical energy to mechanical energy and operate on the principals of magnetism and electricity to rotate. This is done by varying magnetic fields in a rotational motion around two parts of the motor, the rotor and stator, to cause attractions and repulsions leading to motion. The rotor is the rotational part that actually moves and the stator is stationary around the rotor with a very small air gap. In hybrids, the motor may also be used as a generator to charge the battery either through braking or by the internal combustion engine (ICE). When the motor is turned mechanically without applying electricity, it generates electricity that is stored in the battery for later use. There are different types of motors such as induction, permanent magnet, and switched reluctance.