The trend towards decentralized circuit engineering is continuing not only in data distribution but also in power distribution. In conveyor systems, the 400 V AC cabling comprises a significant part of the overall system. It is here in particular that the advantages of INTERBUS and decentralized circuit engineering are now being used as well. Conveyor systems typically include machinery with few I/O points but a large number of drives distributed over a wide area. The power is generally supplied from switch cabinets by point-to-point connections, and consequently in parallel, to the drives.

The switch cabinets contain the electromechanical circuit breakers, line protection and motor protective relays. INTERBUS motor control switches now make it possible to convey the power needed for the drives in series from module to module as well as the data, thereby establishing a power bus. Heavyweight drive cables are consequently replaced by one power cable. This also makes for better EMC conditions because switching the drives from the central switch cabinet creates an interference spectrum extending over hundreds of meters along the entire system. Now, the interference is restricted to the connection cable from the INTERBUS motor control switch to the drive, and the distances involved here are generally no more than 2 meters. Fully electronic switching at zero motor current further contributes to electromagnetic compatibility and, consequently, to the stability of the entire system.

The INTERBUS motor control switch contains all functions needed locally. At the same time, INTERBUS motor control switches can be operated in association with all other INTERBUS-capable devices without any difficulty.
There is no need for the complicated procedure of extending switch cabinets. In addition, stock-keeping is simplified thanks to the small number of module variants required.

Conveyor systems with many
drives are especially suited to
the use of INTERBUS motor
control switches

On Site
INTERBUS has been used successfully for more than four years at the Mercedes-Benz plant in Bremen. The planners in the body shop there have decided in favor of the INTERBUS motor control switch. A new system has been built which serves simultaneously as a buffer and for supplying the bodies-in-white to the subsequent painting operation. Single and double-channel INTERBUS motor control switches have been integrated into the conveyor system for direct and reversing operation.

Dipl.-Ing. Hermann Brake is responsible for the electrical planning of conveyor systems in the body shop. He described the advantages of these decentralized function units with their power bus. For example, there was no need for additional switch cabinets because the modules were installed locally, thereby saving space. It was possible to connect position sensors such as limit and proximity switches on the conveyor line directly to the integrated digital inputs without the need for extra components. Three-phase motors with integrated brakes are used for positioning and are controlled directly by the INTERBUS motor control switch. The possibility of transferring data and power in series from module to module through one cable each produced palpable savings in cabling and cable routes. The clear status display and fault diagnosis on the spot in conjunction with the low-maintenance technology and the associated high level of availability of the system provided further reasons for using the INTERBUS motor control switch.

Dipl.-Ing Mario Naber