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As the body of dry-type transformers

Text: [Big] [middle][small] Release date: 2014-3-26  Views: 330
  As the body of dry-type transformers and cores exposed to the air, if the ambient humidity can cause the insulation resistance drops , supposed to ? Read on.
     If the insulation resistance can reach 10 MΩ / KV ( core -to-ground resistance is greater than 1 MΩ) or more, as long as there is no condensation coil surface , the product can be run directly cast net , with the process of running the transformer temperature rise , the insulation resistance will gradually back to normal.
     If the insulation resistance is less than 10 MΩ / KV ( core -to-ground resistance of less than 1 MΩ) , the following methods that deal with it .
     If a transformer slightly damp, direct rays of light bulbs can be used to bake big , but a longer time , usually about 10 days , when the fan is on better baking results ; . attention away from the main bulb not too close oh , half a meter on well, otherwise I might damage the insulation body .
     b. If the insulation resistance is greater than 2 MΩ / KV ( core -to-ground resistance is greater than 0.1 MΩ), the no-load method can be used for baking . So what is the no-load law? About to open the high side , low side through the rated voltage ( typically low- rated voltage product 400V, can pass the 380V mains voltage ) baking four hours cast net can meet the conditions . It must be noted the high side voltage of up to a million volts , we must do the work when powered up security to prevent someone broke .
     c. If the transformer severe damp, especially once immersed in water , the method must be shorted . Well the short-circuit method , namely the low side with copper shorted ( shorted copper cross-section and low-pressure outlet copper equivalent) , the high-side pass impedance voltage does not exceed the three-phase power . For example , high-pressure 10KV, impedance 4 % / 6% ; or high 6.3KV, impedance 6 % of the products , high voltage three-phase 380V mains can be carried out directly through baking , but the high-voltage power line cable section must not be less than 3A/mm2.