Copyright 2008 to the present, Parker Hannifin Corporation Page 1Parker Hannifin 2008 Global Mobile Sales Meeting & SymposiumWhitepaper # 0001How, Why, and When to apply electric motors to mobile hydraulic Automation Group Electromechanical Automation Division2101 North Broadway, New Ulm, MN reduction, efficiency, emissions, on-demand)The price of fuel has almost doubled over the last year and a half.Up to this point, fuel has been relatively inexpensive.Most companies werent concerned about fuel conservation, fuel efficiency, mpg, or gphconstruction equipment or a mobile vehicle.That has changed.
Now the world hasrecord high fuel prices and fuel conservation and fuel efficiency are openly being This has led construction equipment manufacturers and any mobile vehicle suppliers, who normally are using full hydraulic systems, to try to find ways to make their hydraulic systemsor mobile vehicles more fuel efficient.We all know about the Toyota Prius hybrid automobile,but what about the Caterpillar D9E electric dozer? There are now more mobile equipment manufacturers moving from full hydraulics to electro-hydraulic systems.
A electro-hydraulic system is simply the integration of an electric motor or servo motor to a hydraulic pump, along with the necessary electronics and controls.This sounds somewhat simple to implement, and it can be straightforward, once the basics are understood behind an electro-hydraulic There are similarities between a hydraulic and an electro-hydraulic system.Take, for example, the mechanical makeup of a hydraulic system.There is the oil reservoir, hydraulic pump, and control valves.Driving this could be an IC (internal combustion) engine of some type.
The comparable electric system would be a battery (for storage), electric servo motor / generator, an amplifier (or inverter) for controlling the motor and, again, an IC When comparing a hydraulic pump to an electric motor even the formulas for basic HP is similar.HP = T (in-lbs) x RPM / 63025HP = Pressure (psi) x Flow (gpm) / 1714 Copyright 2008 to the present, Parker Hannifin Corporation Page 2As can be seen, motor torque corresponds to hydraulic pressure, and motor rpm corresponds to pump flow.In a hydraulic-based, mobile system, a diesel engine (or any IC engine)drives a hydraulic pump to create hydraulic power.hydraulic throughout the vehicle.
In an electro-hydraulic system, the diesel engine will now drive an electric generator, which now generates electric power vs.hydraulic power.This electric power is distributed throughout the mobile vehicle.
That electric power is now used to run an electric motor,which now drives a hydraulic pump.The electric power is also used to run any other electric device on the mobile vehicle, such as electric fans, AC units, or power steering pumps
.Any excess electric energy is stored in batteries or capacitors for later use.When a servo motor is provided with electric energy, it converts this electric energy into rotational motion.That same electric motor can also be a generator, whereas rotational energy back-drives the motor, and this rotation is converted into electrical energy.This electrical energy can now be stored in batteries, much like a hydraulic accumulator stores hydraulic It must be noted that not all mobile vehicles will implement a full electro-hydraulic solution.This is dependent upon the HP needed for a certain action.
A typical front-end loader may use an electro-hydraulic solution to raise and lower the bucket.The power required to do this may be in the 50 80 HP range.That same vehicle would probably notuse electro-hydraulic for vehicle propulsion.
Some construction vehicles need power to propel the vehicle well in the 300 400 HP range; most electric motors can not supply that power easily.It is common for most hydraulically experienced engineers to be very familiar with how a hydraulic system is configured, what the terminology is, and how to implement a hydraulic system.Those same engineers may not be familiar how the electric side of a hydro-electric system is configured, what the terminology is, or how to implement an electric motor, drive, and controls on a vehicle.The components of the electric side of hydro-electric will now be AC Induction TechnologyThere are a few electric motor technologies in the market.
The most common are AC induction motors, and the other technology is AC servo motors.
most familiar withan AC induction motor.That motor technology is very old and is by far the most common motor technology out there.
It is simple to use.You merely plug the motor into a wall outlet and the motor runs.
Most water pumps, house fans, and industrial-based hydraulic power supplies use this technology.The power output of an AC induction motor is from fractional HP to over 1000 HP.The disadvantages of AC induction motors are theyare a low energy efficient motor, in the 70% - 80% range at best.Another deficiency of AC induction motors is they have a very poor powerdensity (power (HP) / volume), meaning they are large and heavy relative to the amount of power it can produce.A drive or inverter can be connected to these motors to allow the motors to run at a variable speed.This drive is relatively inexpensive to operate an AC induction motor.A major advantage to an AC induction motor is its low cost.AC induction motors use outer copper coils and iron bars on the motors rotor to cause motor rotation.There are no magnets in an AC induction motor.Due to the absence of magnets, this motor is relatively inexpensive, compared to a permanent magnet AC motor, which will be discussed next.Since there are so many of
Copyright 2008 to the present, Parker Hannifin Corporation Page 3these motors produced yearly, it is a commodity item.AC Servo Motor TechnologyThe permanent magnet AC servo motor, on the other hand, is a newer technology, is
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