New construction and retrofitting of utility vehicles

Consistently-increasing legal specifications regarding emissions place high requirements on utility vehicle manufacturers. As a substantial reduction of fine dust and nitrogen oxides has already been achieved through the previously-imposed exhaust emission levels (1-German Federal Environment Agency), it is now time to address CO2 emission levels. According to the current plans created by the EU States, these emission levels are to be reduced by 30 percent in comparison to 2019 by the year 2030, with an intermediate target of 15 percent by 2025 (2-Reuters). As the already-efficient combustion motors offer little to no optimization potential, the only possibility to achieve this target is to switch to low-emission drive types with a battery or fuel cell. In both cases, the power transmission takes place electrically.

One important step towards this future has been achieved with the ELIAS project, which was funded by Bayern Innovativ. The basis for the project is a standard semi-trailer truck by MAN, which has been retrofitted to become a battery-powered electric vehicle. The companies participating in the project are Ansorge Logistik as user, Toni Maurer as vehicle manufacturer and Sensor-Technik Wiedemann (STW) as electronics specialist for drives, energy management and safety. However, the companies wanted to achieve more than just retrofitting an electric drive into a vehicle. They wanted to maintain the driver and cabin comfort. The drivers should not have to suffer limitations and should be able to operate the “new” truck in just the same way as they would operate a diesel truck. The only thing they should notice is a positive feature, namely the improved driving dynamics of the electric motor. With ELIAS, it has been possible to fulfil all these demands. In addition, all specifications and standards have been observed, meaning that nothing stands in the way of a KBA (Federal Motor Transport Authority) approval.

From this project and over 15 years of experience in the execution of electrification projects, the powerMELA electrification module was derived. This product facilitates short development cycles for complete electrification projects. In addition to the eDrive package, which deals with all traction tasks, the eNergy package must be able to handle the energy flows between the energy sources and the consumers. The eSystemize package deals with the project-specific adaptation, the auxiliary and working drives and the thermal management. This system-specific component for cooling or even for the temperature control of all electrical components is to be executed both application-oriented and customer-oriented. Depending on the lifetime requirements, thermal management can be expanded to form a complex structure. Superordinate to all of this is the eMobilize data management package. The data important for the system is connected via V2X with intelligent load, fleet and infrastructure management systems, and in this way ‘eMobility as a Service’ can be offered. 

The core of the modular drive package are the two 140 kW synchronous motors (STW designation: powerMELA-C). These transmit power to the existing gearbox in the basic vehicle and ensure that the necessary torque is applied to the axle. Through the integration of the converter into the motor housing, the wiring between the converter and the motor is no longer required and an enclosed, compact unit results with a protection class of IP6k9k. Through the use of the automated gearbox and the precisely-controlled synchronization, the driving performance and comfort of the electric truck are substantially increased in comparison to conventionally-driven vehicles.

Drives in the commercial vehicle sector have to fulfil a multitude of different requirements, above all with regard to robustness. This is a decisive criterion, as only by robust components the economic viability via the lower TCO can be realized for the vehicle’s lifetime. And the lifetime demands plenty from the components: whereas 250,000 km or 2,000 operating hours are stipulated in the technical specifications for a mid-range car, 1,500,000 kilometers or 30,000 operating hours are demanded for utility vehicles. And if requirements are stipulated for off-road use, these are no less severe: the operating duration is frequently determined as twelve years and the operating hours lie within a similar range as stated above. The powerMELA-C drives have been dimensioned precisely for this market, and have proven their worth daily in field applications for many different customers. There are hardly any harsher conditions than those under which the powerMELA system operates in the Pistenbully 600E+ by Kässbohrer. Snow, icy temperatures, frost, vibrations and stone impacts demand optimum quality for problem-free application – and the powerMELA is able to provide this.

Electromagnetic compatibility
Another interesting development is a retrofit which breathes new life into older vehicles fitted with expensive, special superstructures. And yet what use is the lowest-emission vehicle if it is no longer possible to register it due to the electromagnetic compatibility acc. ECE-R10? According to information from the TÜV SÜD (Southern German Technical Inspectorate), a substantial proportion of electrification projects fail to comply with the stringent regulations, as no approval for specific use can be issued if the vehicle does not pass the EMC acceptance. In addition to the individual vehicle’s ground, potential equalization and interference suppression concept and the loss-free power distribution in a Power Distribution Unit (PDU), the quality of the components plays a significant role. The powerMELA drives fulfil these requirements and support the vehicle manufacturer through the compact integration of inverter and motor, as the error source “wiring” between the power electronics and the drive motor is no longer required.

A potential-free high voltage system on the vehicle without contact to the chassis provides the required safety standard for mobile machines. Yet this systemic safety collapses if components have to achieve their electromagnetic compatibility through excessively large interference suppression capacitors (y-capacitors) which bridge the insulation. So that no lives are put in danger, contactable wiring systems may not contain over 200 mJ of energy (source: ISO 6469-3). Of course, all cables and plugs are touch-protected, but this hazard cannot be naturally perceived by people, as it is invisible. For this reason, particular focus must be placed on the leakage current balance in the system structure. Only those components may be used which fulfil these requirements. The special structure of the powerMELA drive components guarantees maximum safety with simultaneously low electromagnetic emissions.

Modularity plays a major role for many manufacturers. Only in this way a functioning electrification assembly can be developed using the comparatively expensive components, which can then be rolled out across an entire product range. The performance necessary in the drive line is defined through the customer requirements. An 18-ton distribution vehicle requires a different drive configuration than a 40-ton semi-trailer truck.

For this task, STW has developed a drive package in collaboration with Rögelberg Getriebe. The powerMELA-duo280 is supplied together with two powerMELA-C140 drive units, sensors and a computer unit, the eDrive-Controller. Depending on the drive performance required, several machines in the C series can be combined and electronically synchronized. This offers the advantage that the modularity of the drive line can be substantially increased across the entire OEM fleet. Vehicle gears can be directly further utilized via the SAE1 flange, whereby the degree of effectiveness of the system becomes independent of the load point of the individual machines.

No questions need to be raised regarding the basic structure of the vehicle, as the drive package integrates itself seamlessly into the existing CAN-based vehicle architecture. The entire J1939 environment remains as it was in the standard version, meaning that the typical drive line participants such as brake management systems or chassis controllers can be retained and permit safe operation of the vehicle.

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