Truck & Off-Highway Engineering - June 2022 - 22

EXECUTIVE VIEWPOINTS
As electric drives replace diesel engines to power the
implement's hydraulic pumps, leading hydraulics providers
are engineering a new generation of pumps and
other hydraulics components. Until recently, hydraulic
pumps have been designed around diesel engine
speeds, noise levels and engine frequencies, among
other characteristics. The next generation of hydraulic
pumps are designed to couple with electric drives, operate
optimally with the natural frequencies of electric
motors and respond more efficiently to drives with a
much greater range of speeds, rather than the low idle
and high idle of a combustion engine.
Smart mobile electronics
High-performance gearboxes,
such as the Bosch Rexroth eGFT,
combine space-saving designs with
high-power density and provide
the optimal gearbox ratio for the
extended electric motor speeds.
utility line, so the diesel engine doesn't have to run to power the
drivetrain or implements. Or the engine can be operated in a loadleveling
mode where the unused engine power is used to charge the
batteries in the system.
Full electric: These are battery-powered machines with the capacity
to support extended periods of workload and can recharge between
shifts or use replaceable batteries if a charging infrastructure
is not available.
Major technology suppliers such as Bosch Rexroth have launched
new mobile-equipment electrification platforms designed specifically
to meet the demands of the 700-volt industry segment with motorgenerators
and inverters to support performance ranges from 8 to
200 kW. In addition, there have been advances in gearbox technology
specifically designed to deliver maximum productivity and efficient
use of power when combined with electric motors. These
high-performance gearboxes combine space-saving designs with
perfect matching of the gearbox ratio for electric applications.
Electro-hydraulics for powering implements
To succeed, mobile-machine electrification needs robust, reliable
technology to ensure the machine's implements have the power
needed to do their jobs. Electrification in off-highway applications
must make optimum use of electric and hydraulic components. It
takes a certain amount of power to enable the implements to handle
the job, which calls for hydraulic pumps, valves and electronic controls
that are both compact and powerful enough to fit into tight machine
enclosures while providing the required performance.
22 June 2022
One of the most critical " enablers " of electrification
of the 700-volt mobile-machine segment is the major
improvements in electronic controls. Sophisticated
advances in power-management software created
specifically for heavy-duty mobile machines are making
it possible to stretch mobile-machine duty cycles
without compromising equipment performance or
productivity.
This efficient power-management software is not
limited to managing drivetrain power consumption.
Leading technology suppliers also have advanced implement
controls that build on in-depth expertise to
optimize hydraulics performance.
For example, electronic load sensing (eLS) is an established
controls technology that adjusts the hydraulic
pump displacement dynamically, based on flow
requirements at different actuator load levels. The
newest version of this kind of technology combines
electric-powered hydraulic pumps with pre-compensated
valve platforms, such as the RM mobile control
valve, to more reliably ensure that the required hydraulic
power is available and integrates advanced
recuperation to maximize machine efficiency.
The newest generation of 700-volt electric motors
and inverters, along with a new generation of gearboxes,
hydraulic components and controls, is rapidly
advancing the pace and potential applications for diesel-electric
and battery-electric heavy-duty mobile
machines. It's also clear that hydraulics has a vital role
in these machines, due to the reliability and power
density that only hydraulics can supply. As off-highway
OEMs expand their electric portfolios, there are
advantages to working with technology suppliers with
broad experience designing solutions that utilize both
kinds of technologies to advance mobile-machine performance
and value.
Enrique Busquets, director of Product Area Mobile
Electronics and Electrification at Bosch Rexroth, wrote
this article for TOHE as part of the annual
Executive Viewpoints series.
TRUCK & OFF-HIGHWAY ENGINEERING
BOSCH REXROTH
Truck & Off-Highway Engineering - June 2022

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