Higher-precision work processes, more accurate diagnoses and an immediate quantification of harvest results: in agricultural machinery engineering, much speaks in favor of using a 48-volt system that makes it possible to replace some of the mechanical and hydraulic drives with electric motors. Working hand in hand with agricultural machinery manufacturer KRONE, IAV is therefore developing a demonstrator that reveals the potential of electrification using the example of a mower unit.
Two subsystems of the mower unit are being electrified within the project: the conditioner and the cross conveyor belt. The conditioner has the task of breaking down some of the wax layer on the grass directly after mowing by bending and crushing it (splicing). “This speeds up the drying process significantly – from four days to, ideally, just one day”, reports Reinhold Bals, project manager for commercial vehicles at IAV. With the cross conveyor belt, the farmer can choose between wide spreading and windrowing for drying mown grass.
The KRONE mower unit on which the project is based uses a mechanical drive for the conditioner. It is provided with mechanical energy from a shaft and can be put into three different operating modes by means of a manual transmission. The cross conveyor belt draws its energy from a hydraulic system and can be matched to prevailing requirements by means of a speed control system. The planned demonstrator is to show which benefits are provided by electrifying part of these two functions.
As today’s tractors do not yet have a 48-volt electrical system, the electric energy is currently produced by means of a generator connected to the mower unit’s drive shaft. Using electric motors instead of mechanical or hydraulic drives as shown here, it is possible to provide an additional function on the conditioner or control the speed of the cross conveyor belt with greater precision.
E-motors deliver servicing information prior to harvesting
But these aren’t all of the benefits to come from partial electrification: “Power consumption of the electric motor at the cross conveyor belt also provides a good gage of the quantity currently being harvested”, says Bals. “And even before harvesting, the power consumption of both motors gives an indication of whether the bearings are showing wear. This lets the farmer know in good time whether the mover unit is ready for use or needs servicing.”
The existing 12-volt electrical system provides no alternative to electrification with 48 volts. At a current of no more than 250 amperes, it can deliver a power output of three kilowatts – far too little for the electric motors needed. Highvoltage systems might be a solution. In agricultural machinery, however, a gradual introduction is only expected after 2020. This makes the 48-volt electrical system so interesting in the short and medium term. With its voltage being four times as high, it provides up to 12 kilowatts which is perfectly adequate for partially electrifying a number of functions. Added to this are the lower production and servicing costs for the low-voltage system. “Our aim is to use 48-volt motors from mass-produced passenger cars in partially electrified agricultural machinery”, says Bals. At the moment, industrial systems are still being used which are far more expensive than automotive products.
The project with KRONE started in spring 2018 and is set to run for a year. The mower unit demonstrator is to be available as early as fall 2018 when it will show the benefits of partial electrification in practice too. But that is not all: in future, other agricultural machines, such as seed drills, balers and forest harvesters, can also benefit from the 48-volt electrical system.