Electric machine Compact and revolutionary—new electric machines for off-highway applications

Related Vendors

Liebherr-Components AG

FAULHABER Drive Systems

Taiwan Machine Tool & Accessory Builders' Association (TMBA)

Wuxi InfiMotion Technology Co., Ltd.

A new permanent magnet machine for mobile off-highway applications provides a significantly more efficient, safer, and low-maintenance alternative to hydraulic motors. With the same power density as a hydraulic motor, the electric machine offers other crucial advantages.

In mobile work machines, operational safety, robustness, durability, and efficiency have always been important—as well as compact designs. Until now, hydraulic motors have been able to offer a power density that met the high demands of mobile applications such as excavators, wheel loaders, and telehandlers. Now, Liebherr introduces a new design of permanent magnet machines. It comes with the same power density as hydraulic motors, but without the efforts and risks that the extensive piping systems of these motors entail.

In permanent magnet synchronous machines (PMSM), magnets generate a constant magnetic field in the rotor. The rotating magnetic field of the stator pulls the rotor synchronously along, as the magnetic poles strive to align with the stator field. This creates torque in a low-loss manner, as no electrical excitation is required in the rotor. This efficiency and precision make PMSMs the preferred choice in electric vehicles and modern industrial drives.

Increased machine efficiency to 94 to 96 percent

Liebherr has now optimized the design of permanent magnet machines, increasing their efficiency to 94 to 96 percent. The higher power density of the new motor compared to conventional PMSM was achieved through a combination of several measures. First, a systematic analysis of torque generation was conducted to precisely understand the relevant components and their impact on overall performance. Based on this analysis, precise solutions were developed, with the improvement of cooling identified as the most crucial factor for the increased power density.

In addition to cooling, the mechanical structure of the motor was also optimized, further increasing the torque density and improving the overall performance of the system. A particular challenge was integrating all these individual improvements into an economically attractive overall system without exceeding the installation space of a hydrostat. This was achieved through careful coordination of the various components, allowing the motor to achieve the desired high power density while still fitting into the same installation space as a hydrostat.

A sustainable and future-proof alternative

The directly oil-cooled electric machine, specifically developed for battery and diesel-electric drive systems, enables quick and easy installation as well as the electrification of existing hydraulic drive concepts. Thanks to moderate pressures in the cooling circuit, the risk of leaks is significantly reduced, enhancing safety. Additionally, there is no further danger from emissions, contamination, or accidents caused by burst pipes.

The design of the motor significantly reduces maintenance requirements. The result is less downtime and lower maintenance costs. Additionally, the high torque relative to speed ensures a longer machine lifespan and increases the MTBF (mean time between failures) in the system by reducing gear stages. Liebherr's permanent magnet machines are suitable for mobile applications where compact space, as well as the reduction of emissions and pollution, are crucial.

The efficiency of electric drive systems can be up to twice as high compared to hydraulic systems because less energy is lost in the form of heat.

Permanent magnet machine far more effective than a hydraulic motor

With an efficiency of 94 to 96 percent, a permanent magnet machine is far more effective than a hydraulic motor (approximately 50 percent) and therefore consumes significantly less energy. Even though the purchase cost of an electric motor is generally higher than that of a hydraulic motor, the new electric machines prove to be more cost-effective over the entire lifespan of the applications when considering the operating costs.

The development aims to enable the integration of electric drives into modern vehicle concepts without extensive structural modifications. Particular attention is paid to maintaining common flange dimensions.

Additional efforts in vehicle control are necessary

Nevertheless, the electric powertrain presents new challenges for vehicle manufacturers. Due to the more direct response of electric drives and the changed requirements in energy management, additional efforts in vehicle control are necessary. Furthermore, the high voltages of such a system require extended qualifications for service personnel. Consequently, existing service networks need to be adapted or expanded. However, through proactive design measures, significant added value can be achieved for the company.

The type of primary energy supply does not matter in electric drive technology—even with diesel drives, replacing hydraulic systems with electric drives is sensible, as diesel consumption can be significantly reduced depending on the application.

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