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

full vehicle simulation capabilities for hardware-in-the-loop testing, which was key to controls development and tuning as well as hardware testing. “Finally, our Raptor EVolved demonstration vehicle [see sidebar] has been our field test platform for the powertrain in application,” Kimes adds. “While not necessarily the target vehicle, the process of marrying powertrain to vehicle has provided significant insight into what is required to tune the powertrain for smooth and efficient operation.” Operating modes The outermost of the two motors (referred to henceforth as motor A) is typically integrated with three gear settings, with torque ratios of 3.63:1 in first gear, 1.72:1 in second and 1:1 in third. The inner motor (motor B) has two – 2.64:1 in first and 1:1 in second. These shifts combine to give EMAX’s end-users four driving modes, which SPT calls A1B1, A1B2, A2B2 and A3B2, where A# refers to the A motor’s gear and B# is that of motor B. A1B1 is intended as a heavy launch gear for starting loads or reverse. A1B2 provides a light throttle, and is also useful for launching. A2B2 meanwhile is a midrange gear setting, and A3B2 is for highway speeds. “The control software sets the torque level of the A and B motors with respect to vehicle speed, requested torque and to whichever one of the four ratios the gearbox is in,” Kimes says. “That not only meets the torque demand of the driver, but does so at the maximum system efficiency with respect to potential losses in the inverters, motors and the mechanical power flow path through the gearbox. “We’re able to call it a CVT [continuous variable torque], the reason being that in any of the four modes we can vary the torque from each motor to satisfy torque demand while maintaining maximum system efficiency. “When motor B is changing gear ratio, motor A continues to send power to the output shaft. And when motor A changes ratio, motor B continues acting on the output. So our controller works to have each motor compensate for the other during shifting, to ensure torque interruptions are minimal as power is transferred.” He adds that the EMAX architecture can also work by integrating just a single motor to create a three-speed, for vehicles that require highly efficient all-electric gearshifting but without a second motor. Dossier | Sigma Powertrain EMAX transmission The Raptor EVolved While the primary target market for the EMAX is Class 6 9 trucks (as well as targeting Class 1 6 vehicles with the smaller MID Series counterpart product), SPT has developed its Raptor EVolved demonstrator EV – a Ford F 150 Raptor modi ied to run on an EMAX – to highlight the modularity and applicability of its lagship product. “Putting a Class 9 gearbox in a Class 1 vehicle might seem insane, given that two EMAX gearboxes can move a 230 ton mining truck for 500,000 miles or more, and shift quality isn’t a major issue in really big, heavy vehicles,” Kimes notes. “But putting one in a 2.75 ton F 150 shows just how power-dense our gearbox solution is, and how free from NVH and other quality issues our shifting is. “We retained the Raptor’s 2H, AWD, 4H, and 4L factory capabilities, and designed the extension housing on the EMAX to accept the production transfer case from the truck. The entire 800 bhp powertrain occupied the space where the production 10-speed sat. We it in the tunnel nicely and there were no interference issues between the front axle propshaft and the EMAX.” The EMAX system in the Raptor uses a modi ied DS (Dual Stack) HVH 250 from Cascadia Motion. In this customised system, the motors together produce a continuous torque of up to 960 Nm, and can sustain a maximum output of roughly 800 bhp. “The EMAX can take input torques up to 4600 Nm, so these motors are undersized for the gearbox, but about the right size for an F 150,” Kimes notes. He adds that the maximum output shaft torque in the Raptor EVolved demonstrator is 3009 Nm at A1B1, 2222 Nm at A1B2, 1305 Nm at A2B2, and 960 Nm at A3B2. Also, the Raptor’s transmission to the wheels multiplies this torque by 4.1, for a total traction torque output of 12,337 Nm. The Ford F-150 Raptor EVolved has been SPT’s primary test vehicle and a key demonstrator of how quiet the EMAX is, even during shifts, in the lightest class of EV The EMAX’s motor A acts directly (and motor B indirectly) on an input shaft made from 8620 carburised steel, although this could be made from 5140 alloy steel in the future 22 Winter 2021 | E-Mobility Engineering