ST. PAUL, Minn. – Driving the electrically powered Agco 1386 high clearance sprayer is unlike driving any other hydrostatic or mechanical drive sprayer.
That’s the driving impression of Agco’s David Webster. He has specialized in high clearance sprayers for more than 20 years and has driven just about every self-propelled model ever built. Electric drive beats them all, in his opinion.
Paul Haefner of Agco said he thinks the sprayer is only the beginning for electric drives in farm equipment.
At an agriculture engineering conference in Florida, he said electric drives will also shine in combines because of electricity’s efficiency and the ability to provide constant processor operation independent from ground travel speed.
“The future has a big place for this technology in ag,” Haefner said.
With the Cat C9 turning at 1,850 r.p.m., the electric drive sprayer delivers 35 percent more power to the ground than their conventional 1386 with the same engine, said Webster.
“Not only that, but operator control of the machine is far better than with hydraulic or mechanical drive. It’s very precise.
“The computer has exact control of the speed and torque at each individual wheel. It could have all four wheels running at different speeds if that’s what the situation requires.”
Webster said when making a turn in headlands, each inside wheel slows and each outside wheel speeds up. There’s no scuffing, slipping or rutting.
The same applies in wet conditions. The latest generation of switch reluctance electric motors, like the ones in this prototype Rogator, offers extremely close r.p.m. control. When the computer senses one wheel beginning to lose traction, power to that wheel backs off. There’s no time delay as experienced in hydraulic or mechanical drive.
If the operator decides to stop and back out of trouble, electric motors allow the driver to slow down to a nearly imperceptible crawl, avoiding that fatal first tire chirp that can sink a sprayer.
Although there are different control management techniques for these motors, Agco opted for a simple two-mode system. It operates in either the torque mode or the speed mode. Ground speed is infinitely variable
ABOVE: Agco engineers are looking at ways to turn wasted energy generated by the components into productive power.
RIGHT: This electric motor basically fits into the spot once occupied by an orbital. The latest generation of variable frequency electric motors has no magnets, rotor-bars or slip rings.
within each of these modes.
Electric drive contributes to lower diesel fuel consumption by limiting each of the four motors to the minimum power needed in any situation. Power to each wheel goes up or down as required by conditions.
Although conventional hydrostatic drive enables the operator to manage oil flow and power to a great extent, Webster said they are not as precise as the electric motors.
Compared to their conventional 1386, Agco said the experimental electrically driven concept sprayer has 36 percent higher torque, six percent more horsepower, 20 percent better fuel efficiency and better all around performance.
“The sprayer gets up to speed sooner than the hydraulic drive version and the brakes are better.
“We use electric drive for braking. Our next step is to install technology that allows us to store and re-use that energy when it’s time to accelerate.”
The entire system is made up of off-the- shelf parts. If there’s a weak point, it’s the huge amount of waste heat inherent with electrical power. This requires a liquid cooling system for the generator, four motors, controllers and brake resisters.
Electricity generated while braking is channeled to large shielded resistors that bleed off the heat. Engineers are trying to turn this waste heat into usable energy.
The motors each produce 516 foot pounds of torque and are rated for 50,000 hours, well beyond the life expectancy of a high clearance sprayer. They have no magnets, rotor-bars or slip rings, making them virtually maintenance free. Heavy cables replace hydraulic lines. Each motor monitors its own speed, temperature and position.
Electric motors have an inherent advantage over other power sources because they become more powerful as the load increases. For example, some variable frequency electric motors used in lifting cranes create maximum torque at zero r.p.m.
Electric power has been used on railroads, mining and other industrial equipment for years. While the basic reliability of an electric motor compared to an
orbital motor is obvious, there’s another cost factor that sometimes comes into play with hydraulic drives on sprayers. It’s one thing to burn out an orbital motor while stuck in the mud, which shouldn’t happen as often with electric drive motors.
But it’s quite another sad story when that one fried orbital motor contaminates the entire hydraulic system and leads to other burnouts.
“We think the overall maintenance and operating costs long-term should be considerably less with electric drive. That also means less down time for repairs,” said Webster.
“You probably can’t take all the hydraulics out of a sprayer, but you can plug electric motors into a lot of positions. Once you’ve generated the electricity, you can run wires wherever you need them.
“We can use electricity for the engine fan, air conditioning compressor, hydraulic pump, product pump and anything else you can think of.”
Webster said the experimental sprayer is about 2,000 pounds heavier than it’s conventional counterpart. However, subsequent prototypes will be lighter.
The generator produces 650 volts of DC power, and is designed to operate at 1,850 r.p.m., making it a good fit for the 311 horsepower Cat C9 engine.
“The specs match up perfectly. The engine is right in that sweet spot at 1,850 and that’s exactly where the generator wants to be.”
Webster says the ElectRoGator is intended to let Agco explore the possibility of using electric power throughout a wide range of ag implements, including tractors and combines.