E-Mobility Engineering | January/February 2024 31 the motor shaft torque, and hence the DC bus current. That charges or discharges the bus capacitance, depending on the load current on the DC bus. “This is a little unique to us – particularly as we offer it as part of our controller, rather than as another separate box of electronics. It can be really useful for applications where subsystems like avionics, HVAC systems or hydraulic pumps are also powered off the HV bus, and so the system integrators want to stiffen the bus voltage in the absence of something heavy, like a battery, to regulate it,” Liben explains. “Even if a battery is present to passively regulate the voltage, this algorithm can still help the battery to maintain a particular state of charge amid varying loading conditions.” Testing a trio of controls Determining the necessary parameters to develop speed, torque and voltage control modes began with the generation of high-fidelity flux and inductance maps through electromagnetic simulations. A software-in-the-loop (SIL) model was created, pairing a real-time virtual model of the motor with the actual motor-control firmware for controller architecture development and tuning various gains. Once the SIL model’s performance was adequate, dynamometer testing of real hardware was performed, during which the control response was verified and necessary adjustments were determined for accuracy across the three modes. Field-oriented control (FOC) is the method of choice for smooth motor operation and high dynamic performance, with phase-current regulation performed via space-vector modulation. “The algorithms and firmware are written in-house, as is a self-sensing [‘sensorless’] rotor-position estimation algorithm, used in the HPDM-30,” says Sylvestre. “The -250 uses a resolver, but in the -30 we didn’t physically have enough space for one, so we developed this algorithm.” “For the MW-class powertrains, we’ll use a combination of both, as that will provide a redundancy in determining the rotor position. The self-sensing routine also runs in the background on the HPDM-250 to sanity check the physical resolver’s outputs and function as a fallback in case of a resolver fault,” he adds. While there is only a single controller in the HPDM-30 and -250, a more distributed control architecture has been designed for the -1500, -3000 and other multi-sector, MW-level machines. “The -1500 uses eight independent controllers,” says Sylvestre. “We use a control algorithm, similar to how generators on the electrical grid evenly share load, so that all drive sectors are producing equal torque on the rotor without any controller-to-controller communication, even while they are all in speed-control mode. That’s important from a FMEA [failure mode effects analysis] perspective, because if there’s a fault in one controller, there’s no pathway for the fault to propagate to another.” Future ambitions Having tested and validated its prototypes and their designs, H3X next plans to expand production of the HPDM-30 and -250, while continuing their reliability and environmental testing throughout 2024, as well as the development of its MW-class EPUs. “The high level of shared technology between the kW-class and MW-class machines means the latter are fairly derisked already, but there will certainly be new challenges to solve when we start prototyping them. We’re aiming to have test articles ready to ship to customers for ground testing by the end of 2024,” Sylvestre says. H3X aimed to improve power density by 3x (hence its name) prior to investing millions of dollars in the certification of its products. This ensures that by the time its certified systems become commercially available, they will feature the necessary power density to enable meaningful inclusion in narrow-body aircraft and improve their environmental impact. Importantly, H3X plans for the -1500 to be the first motor it puts through certification with the FAA. Since the product is slated as a core building block for commercial aviation, certifying it first is expected to help considerably in enabling H3X’s future roadmap, including certification and scale production of 9 MW (and larger) electric aircraft powertrains. Key specifications HPDM-30 Permanent magnet synchronous AC motor 12s10p Inrunner IPM rotor SiC inverter Mass: 4.1 kg Volume: 2.07 L Length: 156 mm Diameter: 130 mm Peak torque: 19.6 Nm Peak power: 41 kW Top speed: 20,000 rpm Maximum continuous torque: 15.8 Nm Maximum continuous power: 33 kW HPDM-250 Permanent magnet synchronous AC motor 12s10p Inrunner IPM rotor SiC inverter Mass: 18.7 kg Volume: 8.77 L Length: 282 mm Diameter: 225 mm Peak torque: 800 Nm Peak power: 250 kW Top speed (at output shaft): 2975 rpm Maximum continuous torque: 640 Nm Maximum continuous power: 200 kW HPDM-1500 Permanent magnet synchronous AC motor 96s80p Inrunner IPM rotor SiC inverter Mass: 130 kg Length: 304.8 mm Diameter: 609.6 mm Top speed: 2500 rpm Maximum continuous torque: 5730 Nm Maximum continuous power: 1.5 MW
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