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Volkswagen AG; Kassel (Germany) Selective load protection at VW The common powering of all components by just one power pack has long been normal practice in modern plant and machine design. However, to make sure that faults on one load do not cripple the entire plant, Volkswagen Kassel also provides selective protection in the 24 Volt supply.
On time and selective To maintain system availability in the event of a fault, a defective load circuit must be switched off even before the current limiter of the power pack becomes active and the entire 24 Volt supply collapses. Semi-time lag fuses or line circuit breakers only respond however when the current exceeds many times the rated current. Fast protective devices on the other hand are already triggered by the inrush current peaks of the loads. A dilemma which only a selective current protection like Sitop select can solve. With Sitop select, it becomes possible to selectively switch off a defective branch and switch on loads with high inrush current peaks, for example loads with input capacitances. Above all, failure of the output voltage is ruled out regardless of whether a short circuit or overload exists. Safety in the circuit The Volkswagen AG in Kassel has also found what it was looking for in the diagnostic module. Since the Fall of 2002 it has been producing new 5 and 6-speed gearboxes there which are later installed in the new Golf and Touran at other production sites. Their parallel market launching in the Spring of 2003 also means a challenge for the gear suppliers within the VW company because the planned production rate of 1100 gearboxes a day demands a high plant availability. In every plant section, all the 24 Volt loads are grouped, centrally supplied and monitored by Sitop select. The voltage is divided among the circuits via four output terminals and the trigger current of every output is set between two and ten Amperes. As soon as the current reaches a value between 101 and 130 percent of the set value, the current is switched off after five seconds. At higher values it is limited to just above 130 percent for 50 to 100 milliseconds and then switched off providing it stays above 100 percent. If the output voltage drops below 20 Volts, all output currents of more than 100 percent are switched off so that the power supply to all other branches is maintained. Telediagnosis included Group signal contact and LEDs allow the operator to quickly diagnose the fault on the switch cabinet and repair the defective branch. This helps to reduce standstills to a minimum and the combination of controlled power supply and Sitop select guarantees high availability not only for the assembly line operators. Move Up 3 / 2003 |
