Truck & Off-Highway Engineering - June 2024 - 22

TECHNICAL INNOVATIONS
HYDRAULICS
Electronic torque limiting boosts machine productivity
also experienced electric-motor stalling
problems. In this case, we also needed
a soft starter and inverter for the electric
motor. "
As with hydraulic pumps connected
to diesel engines, pumps connected to
electric motors can induce stalling conditions
when the pump reaches maximum
flow and pressure if there is no
controlled limit for torque. Stalling an
engine or electric motor results in lost
productivity and operator frustration.
One potential solution to this problem
MPG's customer preferred not to use the truck's
diesel engine to power the crane due to increasing
maintenance costs, instead opting for an electric motor.
Electrification isn't just a matter of
switching out the diesel engine for an
electric motor. It requires a thorough
review of connected systems - particularly
the hydraulic system. Using the
same components in electric machines
as those used in conventional machines
often requires more battery power or a
larger electric motor. For this reason,
OEMs have discovered the need to rethink
efficiency and productivity when
electrifying machines.
MPG Makine Prodüksiyon Grubu
learned this firsthand when designing a
truck-mounted electric crane for one of
its Netherlands-based customers. The
Konya, Turkey-based OEM produces
truck-mounted hydraulic cranes with
folding and telescopic booms as well as
aerial work platforms and tree transplanter
machines.
The truck's drivetrain was to remain
diesel-powered, while the crane structure
would be powered by an electric
motor connected to grid electricity indoors
and to a generator outdoors. The
customer preferred not to use the
truck's diesel engine to power the
crane, even for outdoor work, due to
increasing maintenance costs.
MPG conducted a literature review
plus field and market research on electrical
drive technology for the crane. The
22 June 2024
project team selected the electric motor
and driver by making necessary power
requirement calculations and designing
the electrical and hydraulic circuit diagrams,
then proceeded to testing. That's
when the challenges began.
A stalling problem
Veysel Alver, general manager at MPG,
described the issue: " To make the machine
in the simplest way, we designed
it with a three-phase asynchronous
electric motor. When we did our tests
with the piston pump that we use in
existing machines, we could not achieve
the performance we wanted, and we
is increasing the size of the motor, which
MPG wanted to avoid as it would mean
higher costs and a larger space requirement.
MPG engineers determined a
torque-limiting pump could help.
ETL control a problem-solver
Compared to a standard pressure-compensated
load-sensing (PCLS) pump, a
hydraulic pump with electronic torquelimiting
(ETL) control is a highly featured
component ideal for machines with electronic
control architectures. ETL pumps
feature an electronic controller, angle
sensor and electric proportional relief
valve, which together enable active control
of how much power or torque the
pump is consuming. Software controls
the system and the tuning of the pump.
Electronic torque-limiting controls are
either reactive or proactive. Reactive ETL
identifies changes in the system, such as
Electronic torque-limiting pumps bring the same anti-stall benefits to diesel engines, increasing
machine productivity.
TRUCK & OFF-HIGHWAY ENGINEERING
BOTH IMAGES: MPG

Truck & Off-Highway Engineering - June 2024

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