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The power band of an engine or electric motor refers to the range of operating speeds under which the engine or motor is able to operate efficiently. While engines and motors have a large range of operating speeds, the power band is usually a much smaller range of engine speed, only half or less of the total engine speed range (electric motors are an exception – see Electric Motors below). Specifically, power band is defined by the range from peak torque to peak horsepower (or sometimes to redline). For example: combustion engines typically generate maximum torque at perhaps 2500 RPM. The peak horsepower might be 5000 RPM. Such an engine would have a power band of 2500 to 5000 RPM, in which the engine would be very efficient. ==Applications== Since some engines produce their highest power over a relatively narrow range of speeds, a power-splitting device such as a clutch or torque converter is often used to efficiently achieve a wide range of speeds. A mechanical transmission with a selection of different gear ratios is designed to make satisfactory power and torque available over the full range of vehicle speeds. The goal of the selection of gear ratios is to keep the engine operating in its power band. The narrower the band, the more gears are needed, closer together in ratio. By careful gear selection, an engine can be operated in its power band, throughout all vehicle speeds. Such use prevents the engine from labouring at low speeds, or exceeding recommended operating speeds. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Power band」の詳細全文を読む スポンサード リンク
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