Induction Motors — at the heart of EVs
I learnt like many of you did, that Thomas Edison invented the light bulb, but nope he didn’t, he improved on earlier versions that were available through continous research, and for a suprising twist, Elon Musk is not either the founder of Tesla Motors, he is a investor genius who was at the right place at the right time.
According to Brittanica Encyclopedia, “Tesla, Inc., formerly (2003–17) Tesla Motors, American electric-automobile manufacturer was founded in 2003 by American entrepreneurs Martin Eberhard and Marc Tarpenning and was named after Serbian American inventor Nikola Tesla.
Tesla Motors was formed to develop an electric sports car. Eberhard was Tesla’s chief executive officer (CEO) and Tarpenning its chief financial officer (CFO). Funding for the company was obtained from a variety of sources, most notably PayPal cofounder Elon Musk, who contributed more than $30 million to the new venture and served as chairman of the company, beginning in 2004.”
Nikola Tesla whom Tesla is named after, was among the first engineers who successfuly showcased and patented AC commutator-free three-phase induction motors, the other being Galileo Ferraris. Thats when the timeline of induction motors that are the 21st century car electric vehicle engines begun. Far from what we learnt in school science, AC Motors operate differently from DC Motors. Lets see how.
DC — Direct Current Motors
The simple DC electric motor, was invented in the 1820s by Michael Faraday was turned into a practical invention about a decade later by William Sturgeon. Simple explation of how DC Motors work is by using a wire bent into a rectangular loop suspended between the North and South poles of a magnet. This is the current conductor sitting in a magnetic field, which when connected a DC power source produces a temporary magnetic field around it. This temporary field repels the North and South magnetic fields from the permanent magnet, causing the wire to rotate. If a split ring commutator was not used, the wire would stop at that point and then flip back to its original position, but now we can make the current flow in opposite direction in the wire which means it will keep on rotating in the same direction for as long as the DC current keeps flowing.
In a DC motor, the magnet producing a magnetic field is stationery and is known as the stator. The coil of wire carrying the DC electric current forms the rotating part of the motor known as the rotor. The interaction of the stators magnetic field and that of the temporary magnetic field in the rotor makes the motor spin.
AC — Alternating Current Motors / Induction Motors
In an AC motor or at other times reffered to as AC Generator works in a different way but still applying magnetic fields to produce and generate motion and AC Current. A ring of electromagnets unlike in a DC Motor which has magnets, make up the outside known as the stator. These produce a spinning or rotating magnetic field. Inside the stator or what we could refer to as the core is the rotating part known as the rotor which has a solid metal axle, a loop of wires, a coil, a squirrel cage made of metal bars. In an AC motor you send power to the stator coils. This in turn produces a magnetic field that spins around the outside of the motor.
Using the diagram above it is now possible to see how the rotating AC Current whic is about 50 Hz for households creates an electromagnetic field that moves from A to B to C and back to A again to continue the cycle. This field has one extreme end as the North Pole, the other the South Pole. The rotor suspended inside by bearings is an electrical conductor and the stator magnetic field is constantly changing inducing an electric current inside the rotor. If the conductor is a ring or a wire, the current flows around it. The induced current in the rotor produces its own magnetic field and, according to the law of electromagnetism (Lenz’s law) tries to counter the rotating magnetic field by rotating or trying to catch with the rotating outer fields.
Induction Motor Drive train.
The induction motor construct principle gives it the ability to power a HEV or EV drive train or become a power generator using regenerative braking. From commercially available kit above, we see the AC Motor is connected to the gear box whic transfers power to the wheel axle either for front wheel or rear drive or both.
Look out for the next part on how the AC Motor as a part of the EV powerplant drives the car. How the motor RPM ratings are arrived at, the torque, horsepower outputs as well as documented EV land speeds.
