FAQ

• Resource efficiency – 50% less copper for cabling
• Storage provides reduced downtime and increased system availability
• Complete recovery of braking energy – no heat dissipation in braking resistors
• Efficient integration of renewable energy
• Lower power losses due to fewer conversion steps → increased energy efficiency

In the joint project DC-INDUSTRIE, an open DC network for automated industrial plants is being developed and tested. The main areas of research are variable-speed drives, AC/DC supply devices, DC/DC converters for coupling energy storage systems or solar fields, protection and switching devices, connection technology and decentralised network management. The DC network specified in the project is:

• open to all manufacturers and users
• easy to use due to its logical system structure
• energy-efficient because the entire recuperative energy is used
• safe due to the use of fast electronic circuit breakers
• robust due to the division into process-oriented load sectors

Many consumers already require DC voltage (DC) for their operation. For example, in frequency converters, which are required for the speed control of electric motors, AC is first converted to DC in order to generate a variable AC voltage again. DC networks have a central AC/DC conversion. The integration of renewable energies and the use of LED lighting is much easier to achieve. All decentralised AC/DC power supplies are no longer required and the resulting disturbances into the AC supply grid can be significantly reduced.

Since 2018, the project partners have been developing suitable components for the model applications . These are currently running in 9 demonstration sites at BMW, Mercedes-Benz, KUKA, Homag, TH OWL, Fraunhofer IISB and Fraunhofer IPA. Measurements and tests are carried out to validate the system concept and document concrete results.

• reduced feedback effects into the AC grid, eliminating the need for expensive compensation systems
• lower peak infeed power reduces energy cost all year
• peak shaving through integration of short-term energy storage systems
• ride-through capability during AC failure through integration of long-term energy storage systems
• easy integration of renewable energy (solar and wind)
• use of the entire recuperation energy

In a DC network, the energy flow measurement and control are readily available. A higher-level energy management system can record all data and initiate measures for process optimisation, power distribution and avoidance of malfunction .

In the DC network, all recuperated energy is used and is not dissipated in braking resistors. This, together with the elimination of distributed AC/DC converters, saves primary energy. Furthermore, the DC grid allows to easily integrate energy storage systems and renewable energy generators. This is done via DC/DC converters. The AC grid is relieved of both current peaks and current harmonics.

Yes it is. The same guidelines must be applied to the DC network as to AC networks in order to ensure human protection. For safe switching and disconnection, new semiconductor and hybrid brakers have been developed and are used in the model applications.

A frequent concern in industrial production is cost-intensive downtime due to power interruptions. The simple integration of energy storage devices into a DC network enables continued operation even during power failures.

It depends strongly on the application;  however, in the model applications 2-4% reduction were meassured.

The switching device between the grid and the three-phase motor is replaced by a robust inverter (DC/AC converter) with variable speed control. This means that the motor can not only run in start/stop mode, but its speed is also optimally adapted to the process. This minimises energy consumption and power dissipation.