Voltage dips at an automobile manufacturer

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A power quality case study by Michiel Van Lumig

Various departments at a car manufacturing plant are suffering from regular process outages due to voltage dips. These dips are causing production losses in the Metal Operation, Spray Coating, and Assembly departments that directly affect the productivity of the plant. The cost of those losses is directly related to the profile of the voltage dip (duration and depth).

 

Various options to reduce these costs are investigated, with particular emphasis upon the Spray Coating and Assembly departments. The following conclusions can be drawn:

  1. The number and type of dips occurring at the point of connection of the plant is regular. It is similar to what is monitored at other medium voltage stations that have the same grid structure.

  2. A detailed analysis of the spray coating process reveals that installing a ‘restart on the fly’ system on the large conditioning fans substantially reduces the related voltage dip losses.

  3. A detailed analysis of the Assembly department shows that there are two main bottlenecks that determine the restart time after a dip (the ‘Drive’ sub-process and the ‘Cockpit’, ‘Marking’, and ‘Transport chain’ users). These bottlenecks can be removed by installing a Dynamic Voltage Restorer (DVR), which results in a payback time of 1.4 years.

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