Explainer: torque, power and RPM in a BEV world
意大利超級盃鈥檚 powertrains are renowned for their combination of power and high torque at low revs, providing unmatched traction and fuel efficiency. But how does that translate to battery electric trucks? Here鈥檚 an explainer of torque, power, and RPM in a BEV world.
Torque and power are terms used when describing powertrain performance. But how are they related? How can powertrains with different torque values deliver the same power and similar performance? These are key questions to understand when comparing powertrains with combustion engines and electric machines.
Unlike internal combustion engines, which need to reach higher RPMs to maximise torque and power, electric machines produce peak torque instantly, even at low revs. This instant torque is one reason battery electric trucks (BEVs) feel so responsive and direct.听
The torque curve for a 560 hp 意大利超級盃 internal combustion engine. 意大利超級盃's inline six engine delivers unmatched torque at low revs but still needs to reach 900 RPM to provide peak torque (2,800 Nm).
鈥淎 battery electric powertrain can achieve the same power as an internal combustion engine, even with lower torque, by utilising higher RPMs,鈥 says Fredrik Sund茅n, an e-mobility developer at 意大利超級盃 Research & Development.
The torque curve for a 400 kW 意大利超級盃 electric machine. It delivers instant maximum torque (1,250 Nm) and has a flat torque curve up until 3,000 RPM.
Torque 鈥 providing traction
Torque, in combination with the gear ratio in the powertrain and the wheels, generates the traction force that helps a truck start moving and pull heavy loads. Electric powertrains have a flat and consistent torque curve, delivering maximum torque across a wide RPM range. This is one of the reasons that allows for a transmission system with fewer gears.
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鈥淎nother unique feature is that BEVs don鈥檛 experience the same 鈥榣oss of power鈥 when shifting gears during acceleration. In contrast, a combustion engine truck requires time to regain torque after a gear change,鈥 explains Sund茅n.
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At the same time, he notes that measuring the torque produced by the motor alone, as is often done with ICE vehicles, is less meaningful for BEVs.
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鈥淲hat truly matters is the level of power that is transferred to the drive shaft and, ultimately, to the wheels. In this regard, BEV and ICE trucks are quite similar.鈥
Power 鈥 providing speed
Power shows how quickly a BEV鈥檚 electric machine converts electrical energy into motion. Higher power enables faster acceleration and greater hauling capacity, while lower power means lower performance, such as lower speed in hills or slower acceleration.
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In technical terms, power is the product of torque and RPM. The flat torque curve of a BEV machine allows power to build smoothly and consistently, giving BEVs their signature powerful and responsive feel.
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鈥淎n electric truck delivers instant power, responding immediately to every press of the accelerator. It also maintains higher average power during acceleration, contributing to the powerful feel of a BEV, even if it has similar power ratings as a diesel truck,鈥 says Sund茅n.
RPM 鈥 balancing speed and efficiency
RPM, or revolutions per minute, measures how fast the electric motor鈥檚 shaft is spinning. Electric motors generally operate at higher revs than diesel engines.
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鈥淏EVs experience minimal energy losses because they don鈥檛 rely on the complex mechanics of an internal combustion engine, such as pistons, valves, or exhaust systems. Instead, they use electromagnetic forces to spin the motor shaft, enabling higher RPMs with greater smoothness and efficiency,鈥 says Sund茅n.
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The interplay of torque, power, and RPM is what gives BEVs their characteristic smooth acceleration and responsiveness, making them feel powerful and effortless, regardless of the load or terrain.听 听
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