Inductive power transfer is nothing new. Conductix-Wampfler has been using the technology for more than 20 years and has created an established solution with the Inductive Power Transfer (IPT) solution for continuous, contactless power transfer for vehicles without batteries on board. The basic principle is very similar to that of a transformer. However, in order to make the system flexible and mobile, i.e. suitable for practical vehicle solutions, the iron core had to be omitted. Today, the system consists of two main blocks with individual coils - the stationary primary side and the mobile secondary side. The primary side generates a higher-frequency alternating voltage from the mains voltage.

With the Wireless Charger 3.0 from Conductix-Wampfler, this task is performed by the stationary IPS (Inductive Power Supply), which is equipped with a status display and intelligently manages the charging process. The magnetic field generated in the ISP (Inductive Stationary Pad), which is mounted in the floor or on the wall, hits the IMP (Inductive Mobile Pad), which is located on the vehicle, without contact and converts the magnetic field back into electricity. This is converted into DC voltage in the connected electronic unit MPU (Mobile Power Unit) and made available so that the batteries can be charged in a defined and demand-oriented manner. The system receives the current charging requirement via a communication interface, typically directly from the battery management system (BMS). The energy transfer is adapted to the reported demand. Alternatively, other operating modes can also be implemented, such as automated charging with fixed default values.

Reliable principle, interpreted in a modern way

Even though Conductix-Wampfler already has many years of experience in the application of inductive charging, the demand situation has changed in recent years and made more comprehensive solutions necessary. The availability of vehicles is becoming a critical efficiency and throughput criterion and the requirements can only be met in automated operation. A forklift truck in single-shift operation can be charged when it is not in use. Today, however, the trend is towards an increasing number of driverless vehicles in logistics. These are subject to high loads and have to enable high throughputs, which minimizes idle and therefore loading times.

Wireless, inductive charging is predestined for automated charging. The dimensions and the solution concept allow flexible implementation and the possibility of using the opportunity charging principle. This means that even small time windows during operation can be used for charging. These can be, for example, buffering sections or waiting areas before and during the transfer of the transported goods. These are time windows that already exist in principle due to the processes in production or logistics. The number of vehicles does not have to be increased because vehicles are parked away in a loading area or are on their way there or back to their area of use. Ideally, such loading areas can be completely eliminated, which in turn makes space available for other purposes.

Another positive side effect of opportunity charging is the short but regular charging processes, which reduce the thermal stress on the batteries and therefore make a positive contribution to their life expectancy. With the plannable energy requirements and regular intermediate charging, the battery capacities that would otherwise be required can be limited if necessary and states of charge in the lower and upper range (state of charge, SOC), which place particular stress on the batteries and therefore have a negative impact on the life cycle of the batteries, can be avoided.

In addition to all these advantages, the Wireless Charger 3.0 also offers mechanical wear-free power transmission, as this is contactless. The Wireless Charger 3.0 also does not require a fan, there is no mechanical wear that limits the service life and no corresponding maintenance is required. Maintenance is limited to a visual status check and occasional surface cleaning in the event of very high levels of soiling. There are no open contact surfaces on the coils or pads. They are fully encapsulated, making them safe to touch and robust against environmental influences. By eliminating mechanical abrasion and open contact surfaces, wireless chargers can also be used in areas that are generally sensitive to contamination, such as clean production areas in the pharmaceutical industry or food production.

A sustainable system approach

The system costs for a Wireless Charger 3.0 are distributed differently than for charging contacts or charging segments. The wireless charger is a system approach, while charging contacts are a system component and require additional equipment such as a power supply and entail maintenance costs. In addition, many contact charging solutions do not allow demand-oriented charging due to their often fixed charging voltage. This severely limits the usability of the battery capacity, as charging cannot be optimized. A wireless charger adapts to the requirements and delivers the required charging voltages and currents. This has an impact on the actual operating costs of a material flow system.

The article appeared in materialfluss 1-2/22.