OEM&Lieferant Ausgabe 1/2018

109 Lenze Schmidhauser www.lenze-schmidhauser.ch Website best technology that is currently available.” Prior to this claim, Proterra decided to use inverters for controlling the auxiliary units. These inverters were specially designed for mobile applications. “We did not want devic- es that are normally used in industrial plants and are adapted a little just for us,” explained Joshua Stewart, referring to the special chal- lenges arising from use of this technology in a bus. In relation to the inverters, these in- clude placement outside the passenger area, robustness when exposed to water and dust as well as the ability to withstand vibrations and shaking. “We chose Lenze because the MOBILE system is modular and works relia- bly”, emphasised Fowlkes. The task of the ‘Mobile DCU 30/30’ double in- verter is to convert the direct current from the batteries into alternating current on a frequency-controlled basis. The alternat- ing current is then used to drive the pow- er steering pump and also the two electric motors for the air compressor. In addition, a further mobile unit – in this case, a DCU/ PSU 30/5.6 with an integrated DC/DC con- verter – supplies power to the German-made HVAC system, which is designed for maxi- mum efficiency. Because power losses in these three areas directly affect the range of the vehicle, the MOBILE system from Lenze guarantees a high degree of efficiency dur- ing DC-AC conversion and also in the case of the DC/DC converter. The electric drive for compressed air and the hydraulics has also been designed in such a way that the frequency of the motor is controlled accord- ing to needs. In this way, Proterra prevents continuous operation of the auxiliary units at uneconomical fixed speeds. This feature saves a lot of valuable energy, which is then available for driving the bus and also helps to extend its range. 19 cents per mile The component devices function so well to- gether that, in its adverts for the Catalyst plat- form, Proterra promises a comparative range of 21.4 miles (34.4 kilometres) per gallon of diesel (3.78 litres). According to the company, conventional diesel buses would only be able to travel three miles (4.8 km) with this amount of fuel. This means that the operating costs are correspondingly low: 0.19 dollars per mile (1.6 km). Similar figures are to be found in the German specialist press. Whereas the electric bus is operated at a cost of 0.09 euros per kilometre, the costs for other types are 0.36 euros for a gas bus, 0.40 euros for a hybrid bus and 0.53 euros for a diesel bus. However, the new technology, which is start- ing to make headway in the USA, cannot sim- ply be evaluated on the basis of the purchase price alone. The out-of-pocket costs are outweighed by the overall operational costs with maintenance savings of up to $237,000 over the lifetime of a Catalyst compared to a diesel-hybrid bus, and up to $151,000 com- pared to diesel. Further cost savings are re- alized since the Catalyst has 30 percent fewer parts than a traditional bus. Thus, there is a substantial reduction in required inventoried parts. There are tremendous health and sustainabil- ity benefits as well. Each time a dirty diesel vehicle is replaced by a Catalyst, emissions are reduced by an astounding 243,980 lbs. of CO2 annually. Particulate matter from tradition- al transit buses contains numerous harmful gases and upwards of 40 cancer-causing sub- stances. A typical diesel bus emits more than 300,000 lbs. of greenhouse gases annually, while a CNG bus emits 312,840 lbs./year and a diesel hybrid emits 221,760 lbs./year. A switch to zero-emission buses, which emit no tailpipe pollution, presents a critical opportunity to cut pollution, reduce oil dependence and make Earth a better place. The right drive from the modular system The MOBILE system from Lenze can make it easier for community decision-makers to reach a decision in favour of the electric bus because the drive technology delivers con- siderable advantages that make e-buses even more economically efficient. This, among oth- er things, is due to the system’s modular de- sign that enables tasks in commercial vehicles to be performed perfectly in terms of perfor- mance and function thanks to the easy combi- nation of appropriately dimensioned modules. Accordingly, all MOBILE module types have the same outer dimensions and interfaces. All the connections are in the form of plug-in connectors, a fact that substantially simplifies installation. Moreover, MOBILE can easily be integrated into existing vehicle systems due to the standardised CAN communication system (CANopen J1939). MOBILE is not only versatile in respect of use, the engineering of the modular drive system is uniform as well. Irrespective of which double inverters, DC/DC converters or combinations of converters and inverters are chosen, use of the system is always the same - from instal- lation to the commissioning software. This shortens the development and assembly times, avoids time-consuming testing of individual components and reduces the time needed for training. n Jonas Schuster Head of Sales & Marketing Digital BusinessCard Lenze MOBILE system ensures efficiency in commercial vehicles.