It gives Roadster
An improved inverter (PEM) to deliver higher motor current
An improved motor to handle higher current and torque
A new single-speed gearbox
A new motor to gearbox coupler and an improved motor cable
Upgraded vehicle firmware
Power Electronics Module (PEM) Update
It is counterintuitive that one of the most diminutive parts in the powertrain is actually responsible for most of the performance improvement between 1.0 and 1.5. The IGBT (Insulated Gate Bipolar Transistor) inside of the PEM is what converts and regulates power from the battery. These small parts are improving in both efficiency and power handling capability and by integrating the latest generation of parts, TeslaMotors have been able to boost the PEM output current by about 33% from 640A rms to 850A rms with the same number of IGBTs. Since the new IGBTs have improved efficiency they also end up giving the PEM better overall efficiency and improve the range of the vehicle slightly. At most operating points the PEM is already very efficient (95-98%) but every little bit helps.
Gearbox Update
The new gearbox is the most significant change from powertrain 1.0 to 1.5. Tesla have significantly reduced the complexity of this gearbox by getting rid of the need for shifting or speed matching between two gear sets. There is only one set of gears that is always engaged with a ratio of (8.2752:1). There are no clutches and also removed electric oil pump and instead integrated a very efficient gear-driven oil pump into the gearbox. All of these simplifications have saved a great deal of mass and the new gearbox is approximately 45kg instead of 53kg for the old two-speed design.
All these gives Roadster a much higher input torque (400 Nm) and higher speed (14,000 rpm).
One of the most exciting features of this new gearbox (from an EV perspective) that it has extremely low spinning drag (less than 0.1 Nm of dry drag torque.). This low drag contributes to the 1.5 powertrain having a slightly improved range figure.
Range
The PEM, motor cable, motor connections, and gearbox are all incrementally more efficient. When all of these are added up it amounts to a meaningful increase in overall vehicle range of around 10 miles.
One common question is why doesn’t the range drop since the motor current and torque are increasing? The answer is one of the beautiful characteristics of EVs. The efficiency of this new powertrain when compared with the 1.0 powertrain is actually BETTER at ALL of the operating points that they have in common. This is the exact opposite of how two gasoline engines would compare (an 8 cylinder engine versus a 6 cylinder engine for example.) With an internal combustion engine the efficiency of the larger engine is usually worse at all cruising power levels.
When the 1.5 powertrain is operating at torque levels that are higher than what is possible with the 1.0 powertrain a direct comparison is impossible but the efficiency levels are still very high. The efficiency remains relatively flat all the way up to maximum torque and power. Keep in mind also that very little time is actually spent in the vehicle at above 280Nm of motor torque (the previous limit to the 1.0 system) and on the drives where you do spend lots of time at full throttle you generally are not trying to maximize your range!
Thermal Performance
Along with improved efficiency the 1.5 powertrain will have improved thermal performance over the 1.0 powertrain at all common operating points. This is due to the efficiency of the PEM, motor and gearbox and also due to the slightly increased gear ratio. (Increased by about 12% from 7.4:1 to 8.27:1) This gear ratio change will reduce motor current by about the same ratio ~12% for a given vehicle operating point and this will reduce the thermal load on the motor and PEM.
When operated at torque levels beyond the 1.0 ceiling there is no baseline to compare against. One thought experiment is to imagine that the car is driven hard enough to limit motor performance due to temperature. Once in this condition the 1.5 powertrain will always have about 12% more torque to the wheels than the 1.0 (due to the gear ratio) for the same energy dissipation in the motor. Before thermal limit the 1.5 powertrain will have an extra ~33% from the motor plus ~12% from the gear ratio (45% total) better torque output to the wheels than 1.0.
Peak Power
Although this improved powertrain will have ~45% better torque at the wheels it will not have a significantly higher peak power output and it will not have a higher peak battery current draw. (The two are directly related by the efficiency of the PEM, motor and transmission) Tesla Motor’s goal has actually been to keep the peak battery current at the same level (about 650A).
It is best to think about the PEM as an electronic transmission. The car with a two speed transmission didn’t have a higher peak power output either but it could achieve a faster 0-60 mph time because the gears multiplied the motor mechanical torque. Tesla are using the PEM to multiply the battery current by stepping up the current to the motor while we step down the voltage.
– from teslamotors