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

Input motors While SPT is motor-agnostic, it typically selects units from BorgWarner, particularly those from its North American subsidiary Cascadia Motion, and the TM4 Sumo family of motors from Dana. Most prospective customers currently request single-motor, three- speed powertrains, for which they can use COTS motor solutions but with some customisation needed for integrating them into a two-motor system. For example, in the case of the DS HVH250 from Cascadia Motion used in the demo vehicle, SPT typically installs an auxiliary electric pump for further liquid cooling on top of the integrated oil pump that Cascadia includes with the system. That system packages two BorgWarner HVH250 motors. The HVH250 is rated to a top speed of 11,000 rpm, a peak (60 second) power output of roughly 350 kW and a start- up torque of about 425 Nm, with a weight of 57.2 kg. When packaged together in the DS HVH250, total weight is 106 kg, peak torque is 960 Nm, and top power output is slightly above 780 kW. Kimes adds, “Continuous power density in electric motors is all about heat rejection. We focus on that and add auxiliary thermal management; state-of-the-art efficiency demands a dual active cooling system. “Any time we get a request for a powertrain, we input the customer’s vehicle specs and operating requirements into a spreadsheet that very quickly sizes the required motor and axle ratio for the application.” Electromechanical clutches Kimes explains that the EMAX’s gearbox features two kinds of clutch for latching or un-latching the two electric motors to the powertrain. The first are reaction/static clutches, also known as brake clutches, in which the clutch locks the controlled component (typically a carrier, a sun gear or a ring gear) to ground. These types of clutches have one race permanently grounded, while the other race is attached to the controlled component. The other kind is an input/dynamic clutch, where both races of the clutch rotate. These types usually connect input power to a component in a gearset. They are also useful when applied as disconnect clutches in wheels. For its static clutches used in first and second gears, SPT uses the rocker clutch, a radial one-way clutch also found in Ford products. (Kimes invented it when working at Ford.) “At SPT, we’ve modified the profile of the locking elements, and added electromechanical actuation to them,” Kimes notes. “We then package locking elements for the controllable one-way clutch in both directions of rotation, to turn them into two-way controllable clutches.” SPT has different variants of these clutches. Using the nomenclature of 11/00 indicates a two-way clutch that locks into both the power ‘on’ mode and direction of rotation, as well as into the opposite, regenerative direction of rotation. The ‘11’ signifies ‘one-one’ for The two-motor EMAX design uses two sets of planetary gears, each of which consists of a central sun gear… ...and the planet gears in turn engage with an outer ring gear. Which gears drive and which are driven depend on the powertrain mode requested via the ECU ...which engages with four planet gears mounted in a carrier... 24 Winter 2021 | E-Mobility Engineering