Compared to one of the most advanced current metro drive systems, our Get2 rail drive concept – the first EMU multispeed transmission worldwide – combines the advantages of previous ZF applications with potential energy savings and, thanks to greater acceleration, with time savings of up to five percent.
"With our Get2 concept, we clearly demonstrate that we develop our products based on decades of experience; not only for current customer requirements, but with a view to the requirements of the future, which means we are aiming at maximum efficiency," says Lars Kräft, head of ZF's Rail Drive Systems product line. "This first multispeed transmission for electric railcars is groundbreaking in all respects – from hardware, actuating elements and sensors to intelligent control electronics which enable completely new functions."
Thanks to its compact modular design, Get2 can be integrated into extremely tight installation spaces within the bogie according to the customer's wishes. The transmission housing is manufactured using an aluminum casting process, which results in reduced weight.
This multispeed transmission continuously moves the load point in such a way that the electric motor and converter always work in a favorable efficiency range and, thus, consume less energy. At the same time, this provides greater tractive power while offering the same drive power. Therefore, the ZF innovation is particularly well suited for metro applications. Here, the distances between the stops are short and the train has to decelerate and set off quite frequently along the route. Thanks to its two gears and an optimized velocity profile, energy savings or time savings of five percent can be achieved.
Significant ZF competence has been invested in the intelligent shifting strategy that optimally exploits the full potential of the drive and its actuators, which are either controlled electromechanically or by compressed air. Consequently, each unit on all of the vehicle's driven axles can be shifted automatically. Thanks to the smart serial sequence, there are no noticeable tractive force interruptions – the train accelerates without any jolts.
Further potential – also for applications with a large share of driving at constant speed – is offered by the so-called multiple traction system and the additional transmission neutral position. If the neutral position is activated for one or several drive units when driving at constant speed, the coasting function is enabled: All drives that are not required for maintaining the velocity are decoupled and, therefore, do not cause any losses. On the other hand, when decelerating, the multi-speed concept allows for the use of the respective optimal recuperation point of the traction machine. As a result, it is easier than before to recuperate the energy.
Higher tractive force
Get2 makes it possible to increase the starting tractive force until the usual maximum starting acceleration for public local transport is reached, thereby reducing the ride time between the stops. A significantly greater acceleration can also be achieved when the train is at full occupancy. In addition, the two-speed transmission can play off its advantages when slowing the train because it can brake slightly later. Modifying the speed curve results in added efficiency. This also provides new opportunities for public transit with regard to energy consumption and schedules.
In addition, the Get2 concept includes the advanced technologies which are already successfully used in day-to-day operations in the latest generations of ZF's EMU drives. For instance, thrust washers reduce the load on the bearings and housing compared to conventional solutions. More specifically, these are rings that are located on the left and right sides of the drive pinion and slide on an oil film at the output gear. This lateral guidance guarantees that axial forces from the gearing no longer take effect on the bearings and the housing.
ZF has pooled its entire driveline technology competence for rail vehicles in Get2, thus demonstrating the huge potential for significantly reduced consumption, time savings and low life cycle costs without having to cut back on other features: Get2 also offers comfort, reliability, a long service life and easy maintainability.