Problem: high ambient temperatures — a solution for frequent converter failure

Situation:

• Frequent failure of frequency converters in a wind farm at an Italian site exposed to very high ambient temperatures
• An inadequate air flow in the converter section and the hot air given off by the below medium-voltage transformer resulted in extreme temperatures in the converter section. The missing air exchange (no supply of fresh air and no dissipation of used air) resulted in thermal short-circuiting
• Owners were forced to stock large quantities of spare parts on site and tie up respective capital
• The availability of wind turbines was considerably reduced and the overall efficiency of the wind farm did not correspond to forecasts

Solution:

• The problem was analyzed and remedied using the proven DMAIC method (Define-Measure-Analyze-Improve-Control)
• A new ventilation concept was developed for the converter section, using fresh air from the cabinet door and effectively removing exhaust air from this section and the unit through a duct
• Installation of a separate fan, blowing fresh air through the bottom transformer and top converter racks, considerably increased air flow
• The general temperature of the converter was reduced by ensuring the constant operation of the integrated fan

Benefits:

• There were no longer any costs for stocking spare parts
• Availability of the wind farm was increased and the overall efficiency is now as forecasted
• Thermal short-circuiting has been eliminated and the life of the converters now corresponds to their normal service life