While Volkswagen is in the midst of a planned rollout of ten new electric models worldwide by 2026, it is also improving the EV drivetrain technology that will power those vehicles.
The company’s upcoming APP550 rear-wheel drive electric powertrain promises higher performance combined with improved efficiency for the ID models.
VW will plug the APP550 electric motors into its modular electric drive matrix (MEB) platform vehicles, providing an immediate upgrade. The new powertrain has an output of 282 hp with a maximum torque of around 402 lb.-ft. (550 Nm, the source of the motor’s AP550 designation), depending on the vehicle’s gear ratio. For comparison, the electric drivetrain in current VW ID EV models produces 201 hp.
The APP550 motor’s improvements come courtesy of changes throughout, including the stator, rotor, and current from the inverter. The drivetrain includes a three-phase permanent magnet synchronous electric motor, a two-stage single-speed gearbox, and the inverter for the power and control electronics.
The new APP550 electric drive achieves its high torque thanks to an enhanced stator with a higher effective number of windings and a larger wire cross-section. The rotor as its counterpart is equipped with more powerful permanent magnets that has a higher load capacity. The drive was also reinforced with numerous low-friction gearbox components to withstand the higher power and torque.
The current is another relevant factor for the power of an electric drive, so the APP550’s inverter supplies high-phase currents needed for greater power and efficiency. The inverter controls the powertrain through factors such as the clock frequencies and the modulation methods for the generation of the alternating current for the electric drive motor.
The inverter and its controlling software were developed in-house by Volkswagen. In addition to converting the direct current stored in the battery into the three-phase alternating current (this is the inverting that gives the component its name) needed by the electric motor, the inverter also controls the complete energy flow between the battery and motor. During regenerative braking, the inverter converts the generated alternating current into direct current to go back into the battery. All the while, it also monitors the temperature of the electric motor to ensure it stays in the acceptable range.
“Because the available space has not changed, we were compelled to develop a new drive that achieves significant improvements in performance and efficiency in spite of being subject to the same constraints,” noted Karsten Bennewitz, Head of Powertrain and Energy Systems in Development. “That was a great challenge for the team of Technical Development and Group Components. The result shows that we were able to reduce the use of raw materials, while at the same time achieving a considerable increase in vehicle efficiency.”
Electric motors work as part of a system in EVs, so Volkswagen also optimized other portions of the vehicle to squeeze out maximum efficiency.
For example, the cooling system operates without an electrically driven oil pump, relying instead on the gears inside the gearbox to provide pressure for oil supply and distribution. The heated gearbox oil is connected through a heat exchanger to the vehicle’s coolant circuit to keep the drivetrain at operating temperature. The motor’s stator housing has its own water heat sink for cooling.
Volkswagen will build the APP550 drive system with gearbox, rotor, and stator will be produced at its Volkswagen Group Components plant in Kassel, Germany. This plant specializes in the production of transmissions, electric power units, hot-stamped body parts, and exhaust gas purifiers, and has produced more than three million transmissions and electric drive systems employing the largest alloy foundry in Europe.
“We have been developing electric drive motors and their gearboxes for 15 years now and have also been producing them here at our location for over 10 years,” stated Alexander Krick, Head of Technical Development E-Drive, Power Electronics & Transmission at Group Components. “Drawing on our many years of experience, we optimized the overall system through, among other things, the use of special electrical sheets and customized machining processes and were thus able to significantly increase efficiency.”