ISSUE 012 Winter 2021 Sigma Powertrain EMAX transmission dossier l In conversation: David Hudson l 48 V systems focus l 2021 Battery Show North America and Cenex-LCV reports l Everrati Porsche 911 digest l Switching insight l Motor laminations focus

rules Knieper laid out to ensure they could be exported to Embedded C with high fidelity (and subsequently stepped through in the simulator with minimal stress in the event that any bugs were found). “Some unique communications work was needed in the embedded control system too,” Knieper adds. “For example, we wanted to get the Embedded C algorithms to interact seamlessly with the CAN, and the H-bridge control algorithm was written to optimise how smoothly we can ramp up the current when firing the clutches on or off.” Future plans As well as being a motors integrator, SPT is widening its focus on efficiency beyond the EMAX and MID-Series (see sidebar) into motors themselves. Its newest project, the SPT500, is an AC induction motor designed in-house principally to be packaged into the EMAX, to provide turnkey electric powertrains for central drive and e-axle systems. Most recently, SPT has also designed an axle-mounted version of the EMAX (called the EMAXle) for customers manufacturing heavy trucks to run on e-axles. Prototypes of it will follow in the near future. Kimes observes that electric propulsion demand across North America is split roughly three ways: between central drives, e-axles and in-wheel e-motors. As a consequence, SPT anticipates that this region might be the last to take up its e-propulsion solutions, although demand for new powertrains is picking up rapidly among American EV OEMs. Speci ications EMAX powertrain 18 in (45.7 cm, not including user’s choice of e-motors) All-electric Planetary gear sets Maximum input torque: 4600 Nm Maximumoutput torque: 30,900 Nm Minimumvehicle size: Class 1 Maximumvehicle size: Above Class 8 Motor A irst gear ratio: 3.63:1 Motor A second gear ratio: 1.72:1 Motor A third gear ratio: 1:1 Motor B irst gear ratio: 2.64:1 Motor B second gear ratio: 1:1 MID Series While the EMAX has been designed principally for Class 6 9 truck EVs, SPT also makes the MID Series powertrain, a smaller solution embodying largely identical power lows and electrically actuated clutch systems but aimed at last-mile Class 1 6 delivery vehicles. The MID Series uses OEM-validated Ravigneaux gearsets identical to those in the 6R100 Ford transmission used in the F 250, among other vehicles. “Those particular gearsets were ideal because we needed a capable four-node gearset with hard- inished gears, and which was readily available,” Kimes says. “The MID Series is an evolution of an older system called the SST [Sync Shift Transmission] that we made in 2011 12. We undertook a signi icant design change in 2019 to make it modular, like the EMAX. “The newest generation of electric clutches, sensors, controls and case changes were implemented predominantly for commonality of parts with the EMAX, and to allow the MID- Series to be used lexibly across either a central drive powertrain or an e-axle, with minimal changes between the two use-cases.” SPT has recently completed designs for this e-axle version of the EMAX, aptly named the EMAXle The MID-Series powertrain uses largely the same technology as the EMAX, but is scaled for Class 1-6 EVs 30 Winter 2021 | E-Mobility Engineering Dossier | Sigma Powertrain EMAX transmission