Tesla’s Roadster Motor Technology

October 31, 2015 by Donald Krambeck

Tesla Motors was founded in 2003 and is an American automotive and energy storage company. This article will focus on how Tesla's Roadster electric motor works. The basics of the car are pretty standard and straightforward, but the intricate details are much more intriguing. It will also detail the key differences between an internal combustion engine and Tesla's electric motor. At just about the size of a watermelon, the motor converts electricity into mechanical power and also acts as a generator, turning mechanical power into electricity.

At just about the size of a watermelon, the Roadster's motor converts electricity into mechanical power and also acts as a generator, turning mechanical power into electricity.

Tesla Motor's Roots 

In 1882, physicist Nikola Tesla discovered the rotating magnetic field, which is a fundamental principle in physics and one of the most significant discoveries of all times. From this discovery, Tesla constructed his first AC induction motor and he unknowingly started the Industrial Revolution at the turn of the century. Utilizing this invention, a group of engineers founded Tesla Motors in 2003 and sought out to prove to the automotive industry that electric cars could prove to be more suitable than petrol-powered cars. Tesla's ingenious engineers created a brilliant powertrain built around an alternating current (AC) induction motor, patented in 1888 by Nikola Tesla, the inventor who influenced the company's name. The result of this inspiration, The Tesla Roadster, was launched in 2008. The Roadster is the first production automobile to use lithium-ion battery cells as well as having a driving range greater than 200 miles per charge. 


The Roadster battery charging port is on-board the car. This port allows the Roadster to be plugged into any outlet, anywhere in the world. Depending on the outlet voltage and Amperage, the battery pack can be charged in as little as 4 hours from empty. Charging the electric vehicle is available in two different options: a recharging station that provides a 220-volt, 70-amp outlet that charges just in 3.5 hours, or by using a mobile charging kit that allows recharging through any electrical outlet and depends on the outlet configuration (110-volt or 220-volt). 

Efficiency from Electricity

Unlike conventional petrol-powered cars, the Tesla Roadster won't be found with hundreds of moving parts. It's powered by just four essential systems:

- The Energy Storage System (ESS) 

- The Power Electronics Module (PEM)

- A sequential manual transmission

- An electric motor

Tesla's innovative engineers decided to power the Roadster by utilizing stacks of patterned metal plates and wrapped wires to generate an electromagnetic field, also known as a 3-phase alternating current induction motor. This tiny yet extremely durable motor weighs just over 100 pounds. A whopping 375 volts is used to deliver 900 Amps of current into the AC motor to create strong magnetic fields. At peak speeds, the motor can spin up to 14,000 revolutions per minute. 

Tesla Motor's engineers decided to use an alternating-current induction motor over a conventional DC brushless motor because AC induction motors are extremely reliable, simplistic, and efficient at a wide range of speeds. This electric motor takes the place of an internal combustion engine, thus eliminating the need to burn a single drop of gasoline. The motor converts electricity into mechanical power while also doubling as a generator, turning mechanical power into electricity. With this AC motor, torque is available instantly at any RPM. The motor is then coupled to a single speed gearbox above the rear axle. The Roadster has only a single speed gearbox: one gear ratio from zero to top speed. Switch two of the phases electronically and the motor runs in reverse.

While driving to provide a high-performance car, Tesla Motors designed the Roadster with rechargeable lithium ion batteries found in laptop computers. In order to assure the highest quality and safety in the battery packs, Tesla only uses lithium ion cells from top producers. The incredibly small size of the cell enables efficient heat transfer, provides excellent reliability, and extends the battery pack's life. Each battery cell is in a steel case, which transfers heat away from the cell. The battery pack includes sixty-nine cells that are wired in parallel to create "bricks." Ninety-nine bricks are connected in series to create sheets that are inserted into the battery pack. To be exact, there are 6,831 batteries weighing about 1,000 pounds that are found in the Roadster's ESS. A computer is used to control each sheet, making sure all of the batteries are charging and discharging properly. Below is a diagram of how the 11 sheets are fitted into the battery pack casing. 

When the battery has exhausted itself, the cells could be disposed in a landfill. However, the battery pack doesn't contain heavy metals or toxins. Tesla has created a recycling program that reuses over 60% of each lithium-ion rechargeable battery. Of this 60%, the components are recovered in the recycling process and are reused to create new packs. 

The Power Electronics Module (PEM) uses an inverter that changed direct current (DC) to alternating correct (AC). It manages and converts current during driving and charging. As alternating current flows into the car from charging, the PEM converts it directly into direct current to be stored into the battery. The power inverter uses 72 insulated gate bipolar transistors (IGBTs). An IGBT is a three-terminal power semiconductor device that acts as an electronic switch. By using this technology, Tesla Motor's was able to generate an increase in power output. Under peak acceleration, the lithium-ion batteries can produce around 200 kW of energy. Additionally, the PEM controls voltage levels, the motor's RPM, torque, and the braking. This regenerative braking system captures kinetic energy and transfers it back into the ESS. By utilizing this kinetic energy, the PEM and motor systems are around 85 and 95 perfect efficient, allowing the motor to output 185 kW of power. The figure below is the Roadster motor up close, out of the automobile.

Within this electric motor, there are winding coils of copper wire that are stacks through thin steel plates called laminations. The wire conducts electricity that feeds into the motor through the PEM. There are three separate sets of wire and each conducts one of three phases of electricity. If you think of a sine wave, the wave alternates between peaks and valleys. Each phase is offset from each other so when combined, the rises and falls of each phase creates a level supply of current. The flow of alternating current into the copper windings, create a magnetic field. This concept is known as electromagnetism.

The Result

The engineers at Tesla certainly proved to the automotive industry that electric automobiles are more suitable than gas-powered cars. With a driving range of over 200 miles per charge, zero-emissions, and speedy acceleration, the Tesla Roadster is truly a one-of-a-kind vehicle. 

  • redrooster01 November 05, 2015

    I read somewhere recently(probably the Tesla site) that the Tesla S model EV will be powered in the near future with graphene ultra-capacitor/ batteries or as they like to call it now an; Energy Storage Device. Based on Dr Robert Murray Smiths design this battery has twice the energy density of lithium ion type batteries and charges up in 5 minutes instead of 3 and a half to 4 hours,it is safe,non toxic and uses cheap easy available materials.

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    kiwifiat November 07, 2015

    Interesting article, you should note a single speed transmission does not qualify as a sequential manual transmission in usual automotive engineering parlance.

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