Insulation performance of KN1000 outer ring with alumina ceramic coating

       

Insulation performance of KN1000 outer ring with alumina ceramic coating

When the humidity is set to 80% and the temperature is 25 ℃, the insulation resistance values of the three outer rings in each state are as follows:

1) As the length of time placed in a high-humidity environment increases, the insulation resistance of outer ring A and outer ring C decreases sharply within 15 minutes, and the rate of decline becomes slower after 20 minutes, and remains basically unchanged after 40 minutes, and finally remains at 10-15 MΩ;

2) The resistance of the outer ring B begins to decrease at 35 min, and it is 3 000 MΩ at 60 min;

3) After the secondary sealing, the outer ring C still maintains an insulation resistance greater than 11 000 MΩ within 60 minutes.

The outer ring C is ground after sealing. The state of the internal pores of the coating after sealing and grinding is shown in Figure 5 (the hollow in the figure represents the original pore, and the black represents the pore filled by the sealing agent). Since the sealing agent cannot penetrate into some closed pores inside the coating (Figure 5a), and these closed pores may form open pores after the coating is ground (Figure 5b), these new openings are exposed to high humidity. The moisture in the air enters the interior of the coating along the channel formed by the pores, which affects the insulation performance of the outer ring C, resulting in the outer ring A and C showing the same insulation resistance under high humidity. In order to prevent moisture in the air from entering the interior of the coating, the test outer ring C is now subjected to a secondary sealing and curing treatment.

In order to test the effect of long-term high humidity on the insulation resistance of the outer ring, the outer ring B and the second sealed outer ring C were placed under 80% humidity for 15 hours, and then the outer ring insulation resistance was tested. The test result of the outer ring B is 2 500 MΩ; the test result of the outer ring C after the second sealing is 4 500 MΩ, which is higher than the insulation resistance of the outer ring B, indicating that its sensitivity to humidity is weaker than that of the outer ring B. This may be because the outer ring C has been sealed once, but a fresh surface is produced after grinding, and the pores are exposed. The second sealing will fill and block these pores. Under the same thickness of coating, the outer ring C is coated. The number of closed pores in the layer is greater than that of the outer ring B, so the test data of the outer ring C presents the above results