Thursday, July 24, 2008

TESLA-The Electric Sports Car

The Tesla itself - 400 volts of electric potential wrapped in a carbon-fiber body - is as far-out as its namesake, styled like the cars you used to see only in cartoons but charged by a high-powered outlet in your garage. Stomp the accelerator, and thick cables connecting the liquid-cooled lithium ion battery pack to a printed circuit board send all that current into a series of silicon transistors the size of your little fingernail. They are capable of switching as much as 850 amps, which drive the AC motor as high as 14,000 rpm and send the rear-wheel-drive Roadster screeching off the line, with a range of 220 miles on a single charge. Acceleration is so fast (0 to 60 in 3.9 seconds) that you get pushed back in your seat for as long as you dare to keep your foot on the aluminum pedal.
With Charging, It’s Safety First
We’re committed to making sure the charging process and the batteries themselves won’t pose a safety issue to you, your passengers, or anyone stumbling around in your garage.
For starters, the plug on the charging unit only becomes “live” when it is properly connected to the car and both the charging unit and the car have “talked” and agreed the connection is safe to allow the electricity to flow through it. As a backup, the charging connector is designed such that you cannot touch any metal on the charging pins.
The EVSE in your garage protects against many kinds of faults, including ground faults, strain on the cable, and the presence of smoke in your garage. Whenever any fault is detected, charging is stopped and the cable is deactivated.
Energy Storage is All About Safety
Tesla Motors’s engineers selected cells from a reputable Fortune 500 battery supplier that has produced billions of safe, reliable, Li-ion batteries. We combined this basic proven cell technology with our own unique battery pack design to provide multiple layers of protection. Our design ensures that should any cell fail catastrophically, adjacent cells do not. This is true regardless of whether or not the battery pack cooling system is running. (The cooling system in the Energy Storage System exists to increase the battery pack’s life -- we don't depend on it for safety.)
We then collaborated with an outside firm known for expertise in lithium ion battery safety to perform hundreds of tests to validate the safety of our design. In these tests, we set out to simulate a worst-case scenario in which a cell develops a serious malfunction. In each test, we set a cell on fire in the middle of a Tesla Motors battery pack (by heating the heck out of it) and observed the results. Our design contained these failures to a single cell, demonstrating that malfunctions wouldn’t spread.
The Battery Safety Monitor, mounted inside the battery pack’s protective enclosure, measures voltage, current, acceleration, tilt, smoke, moisture, and more. Like the controller for an airbag, the Battery Safety Monitor responds to an emergency - in this case by automatically disconnecting the battery pack from the vehicle and shutting down power to the car and to all electric cables in the car.
None of the Tesla Roadster’s high voltage systems are accessible to accidental contact outside their protective enclosures and jacketed cables. Only with special tools can someone gain access to any high-voltage components. Our high-voltage systems are enclosed, labeled, and color-coded with markings that service technicians and emergency responders already understand.
Tesla Roadster Specifications*
Style -2-seat, open-top, rear-drive roadster
Drivetrain-Electric motor with 2-speed electrically-actuated-manual-shift transmission with integral differential
Motor -3-phase, 4-pole electric motor, 248hp peak (185kW), redline 13,000 rpm, regenerative "engine braking"
Chassis -Bonded extruded aluminum with 4-wheel wishbone suspension
Brakes -4-wheel disc brakes with ABS
Acceleration-0 to 60 in under 4 seconds
Top Speed -125 mph
Range -About 220 miles (based on EPA combined city/highway cycle)
Battery Life-Useful battery, 100,000 miles
Energy Storage System--Custom microprocessor-controlled lithium-ion battery pack
Full Charge -About 3.5 hours
How It Works
When you build a car that's electric, you start with one built-in advantage: Electric cars just don't have to be as complex mechanically as the car you're probably driving now. Sophisticated electronics and software take the place of the pounds and pounds of machinery required to introduce a spark and ignite the fuel that powers an internal combustion engine.
For example, the typical four-cylinder engine of a conventional car comprises over a hundred moving parts. By comparison, the motor of the Tesla Roadster has just one: the rotor. So there's less weight to drive around and fewer parts that could break or wear down over time.
But the comparison doesn't end with the counting of moving parts. The engine and transmission of a conventional car also need lubricating oils, filters, coolant, clutches, spark plugs and wires, a PCV valve, oxygen sensors, a timing belt, a fan belt, a water pump and hoses, a catalytic converter, and a muffler — all items requiring service, and all items that aren't needed in an electric car.
The Tesla Roadster's elegantly designed powertrain consists of just the four main components discussed below. Mind you, these aren't "off-the-shelf" components, and each includes innovations, both small and large. But when you build a car from the ground up, you have the luxury of questioning every assumption — and to distill as you reinvent.
The Energy Storage System (ESS)
When we set out to build a high-performance electric car, the biggest challenge was obvious from the start: the battery. Its complexities are clear: it's heavy, expensive, and offers limited power and range. Yet it has one quality that eclipses these disadvantages and motivated us to keep working tirelessly: it's clean.
The Tesla Roadster's battery pack — the car's "fuel tank" — represents the biggest innovation in the Tesla Roadster and is one of the largest and most advanced battery packs in the world. We've combined basic proven lithium ion battery technology with our own unique battery pack design to provide multiple layers of safety. It's light, durable, recyclable, and it is capable of delivering enough power to accelerate the Tesla Roadster from 0 to 60 mph in under 4 seconds. Meanwhile, the battery stores enough energy for the vehicle to travel about 220 miles without recharging, something no other production electric vehicle in history can claim.

Power Electronics Module (PEM)
Most of the subsystems in the Tesla Roadster are completely electronic and under direct software control. But unlike all other cars, these systems are not a hodge-podge of independent systems — instead, they are designed as an integrated system, the way complex network and computer systems are designed today.
You'll see the hub of this network every time you pop the trunk — the Power Electronics Module. When you shift gears or accelerate in the Tesla Roadster, the PEM translates your commands into precisely timed voltages, telling the motor to respond with the proper speed and direction of rotation. The PEM also controls motor torque, charging, and regenerative braking, and it monitors things like the voltage delivered by the ESS, the speed of rotation of the motor, and the temperatures of the motor and power electronics.
The PEM controls over 200 kW of electrical power during peak acceleration — enough power to illuminate 2,000 incandescent light bulbs.

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