NexxtDrives Variable Speed Power Take-Off Provides Micro Hybrid-Functionality
The first application for the new system was the operation of engine cooling fans for large diesel engines in commercial vehicle and off-highway applications. The power overhead required to run the cooling fan in a typical truck engine installation accounts for about 10% of fuel consumption. As cooling fans are sized and geared to cope with low speed, high load driving conditions, they are wasting power most of the time. According to the companys press release, the NexxtPTO allows fan speed to be matched precisely to engine cooling requirements, resulting in overall fuel savings around 5%.
"The beauty of our approach is that most of the power is transmitted by the highly efficient mechanical transmission," says Frank Moeller, director and chief engineer at NexxtDrive. "The relatively small electric machines give you full control over the speed of the output and the transmission is designed so that the electrical load drops to 0 at the most commonly used operating speed."
The electrical motor/generators in the unit can be sized to replace the engines conventional starter and alternator to give smooth, instant start/stop and mild hybrid functionality. This is especially applicable for applications such as delivery vehicles where the engines spends significant time at idle.
The system can provide controllable mechianical power or can be used to generate sufficient electricity to support significant electrical loads. With the ability to control the speed of the PTO totally independently of engine speed, the fuel consumption overhead required by ancillary equipment is kept to a minimum.
Operation combines electrical and mechanical power transmission using a patented system of epicyclic gears. A belt drive from the engine runs a compact electric motor/generator and a sun gear in the epicyclic gear train simultaneously. A second electric motor/generator uses power generated by the first to turn a second sun gear. Electrical and mechanical power inputs are combined by two sets of planet gears to run the fan or other auxiliary load connected to the planet carrier.
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