Starter-generator stretches fuel economy

Engineers at Siemens Automotive have combined the starter and generator into a single unit small enough to fit on the crankshaft between the engine and transmission in most cars, SUVs, and trucks. The device's sophisticated power electronics let current flow in both directions, so the same motor acts as a starter and, once the engine is operating, as a generator. Because the unit uses a brushless rotor and stator design, the system is virtually maintenance-free, according to Siemens. The starter-generator replaces conventional starter solenoids and motors, alternator/generators, and several gears and pulleys. Overall, the device reduces the size, weight, and complexity of automotive drivetrains. It will also provide more power, and will make it easy to convert to a 42-V standard electrical system for cars and consumer vehicles, says Siemens. It generates up to 8 kW of power across an engine's entire rpm range with an efficiency greater than 80%, compared to a conventional starter/generator's 1.5 kW at 60% efficiency.