Frauscher x Porsche 850 Fantom Air | Dossier 23 E-Mobility Engineering | March/April 2024 Wiring harnesses were also customised to enable toggling of some onboard relays, unlike those in automotive, such as for controlling the coolant pumps and Z-drive, and for managing a dual, redundant safety lanyard or kill-switch system (typical in powerboats). Pulling out the lanyard triggers a message to the eVCU to no longer send out torque requests and ceases the inverter’s power supply to ensure the boat stops. Smooth operation When a change in the throttle lever is output to the eVCU over CAN, it is converted into a FlexRay packet for the inverter to read as a torque command. Several hundred signals are handled in the eFantom at any given moment. These include steering and acceleration commands from the driver, readings from temperature sensors throughout the powertrain for thermal management (including some exposed to the ambient water surrounding the heat exchanger), and driver-relevant values for motor and battery health, which the operator may wish to monitor via a RayMarine display at the helm, such as battery state of charge (SoC), transmitted voltages and cell temperatures. The eVCU also sets the speed and torque logic by which the inverter governs the four driving modes available to the eFantom’s driver, each essentially hallmarked by a different limit to its top speed. These are Docking mode, which caps at 15 kph, a Range mode, limited to 41 kph (the cruise speed for optimum energy efficiency), a Sport mode with a top speed of 75 kph and Sport Plus, which gives the absolute maximum of 85 kph. “Within each of those we have different throttle-response maps; for instance, the Sport Plus regime has a higher acceleration than Sport, Range and Docking, in that order,” Helmberger says. Regarding speed and handling, we asked if Frauscher ever considered or would want to engineer a hydrofoil propulsion system, such as the one discussed in detail by Candela in EME 11 (Autumn 2021). “I can’t comment on future products, but hydrofoiling is something clients have asked us about, and electric powerboating is a small industry, so we know Candela very well and have driven their boats,” Helmberger notes. “What their C8 does is brilliant for their application, because lifting the boat out of the water lets you cover a distance of around 30 nautical miles as fast and energy efficiently as possible. “But the drawback is that hydrofoiling, even when controlled as neatly as theirs is, works most safely and efficiently in something of a narrow speed window, of maybe 25-28 kts. You have to limit the top speed judiciously to avoid unsafe usage, and once you go slower than that it’s not really efficient anymore. “We certainly can’t match their efficiency at their top speeds, but we don’t need to; our boats are used very, very differently to theirs. Our users will only ever want high speed for very short lengths of time, just for fun, and then the rest of the time they’re at a leisurely slow pace, often below 6 kph. So hydrofoiling is of no real benefit to our clients.” Motor and inverter The motor in the eFantom is capable of 170 kW continuous power, or 400 kW peak output – a step beyond the 60-110 kW maximum output levels of Frauscher’s electric boats, developed as they were in a time preceding the While Frauscher is familiar with hydrofoiling systems, they were deemed unnecessary for the eFantom as its users will rarely sail at high speeds
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