59 Inverters | Focus E-Mobility Engineering | March/April 2024 Proof-of-concept integrations are increasingly important to demonstrate the benefits of new systems to vehicle developers. “To squeeze all the potential of an inverter-motor combination into each vehicle is a complex task that requires a lot of engineering knowledge and experience plus weeks of testing. We have seen efficiency gains of 4-7% or torque gains of up to 35% just by swapping to our inverters from other very well-known inverters available in the market,” he says. A 35% gain in torque would require at least 35% more current to be pushed through the motor by the inverter. One of the most significant new demands on inverter technology in recent years has been the move to higher voltages, says an expert from a high-current power-switching, motor control and software company. “We’ve seen the move from 400 V up to 600 V, and now 800 V is about the standard. Whether it will move far beyond that is still uncertain. Of course, the higher the voltage, the higher we can drive the efficiency in the inverter, which will either improve range or reduce battery size. One of the hard limits with voltage is that you need to be certain you can isolate all the systems. Even at 800 V to 850 V bus voltage, you already need to use devices with 1,200 V maximum capability just to withstand the ripples and peaks. If you move beyond that, you intelligent features to work with these systems, including adaptive control algorithms that optimise performance based on driving conditions. Price and charge time In the car and light commercial vehicle markets, EV manufacturers are working to lower the two main barriers to EV acceptance of price and charge time, according to our global automotive technology company. Battery EVs are still a lot more expensive than equivalent vehicles with internal combustion engines (ICEs), and most of this extra cost comes from the very large battery packs that must be fitted to address range anxiety. Such big packs take a long time to charge, so we can add charge anxiety. Charge speed, therefore, has become a differentiator for leading EV manufacturers, the company’s expert says. E-mobility, of course, covers a wide variety of applications, from on-road and off-road vehicles and industrial mobility to marine and aerospace vehicles, all of which have their own requirements, a leading traction inverter and BMS developer points out. Some high-volume, cost-sensitive applications such as two-wheelers are focused on reducing price while increasing safety, whereas aeronautics and related applications concentrate on power density, weight and safety, the company’s expert says. start to get into trouble with isolating distances between all the high-voltage parts,” the expert adds. Key parameters When specifying an inverter to drive a motor, matching its power output with the application’s requirements is fundamental, while high efficiency is essential for making the most of the available power and minimising losses, notes our developer of advanced semiconductors and control algorithms. Switching frequency affects both efficiency and the quality of the output waveform, with higher frequencies enabling the use of smaller passive components (such as electromagnetic interference filtering (EMI) inductors), but potentially increases losses, the expert says. The inverter’s ability to dissipate heat is crucial as it affects reliability, durability and longevity. “The output of an inverter is a controlled AC current with a DC voltage limitation, meaning the DC link limits its capabilities,” says a leading developer of light, medium and heavy-duty traction inverters. “You need to be able to specify the electric machine performance at the minimum DC link voltage, and that determines the current requirements of the drive.” He says the output of the inverter that makes the motor produce torque is current, and both the peak current This Cissoid/Silicon Mobility’s modular inverter reference design drives 350 kW/850 V motors (Image courtesy of Cissoid) Dana TM4 BCI20 bi-directional charger-inverter (Image courtesy of Dana TM4)
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