Dry type transformer test items are divided into conventional test, special test (also called type test). The conventional test is the test that must be done before each transformer leaves the factory, which are respectively:
1. DC resistance test
2. Power frequency voltage withstand test
3. Variable ratio test.
4. Frequency doubling voltage test (commonly known as induction)
5. No load test
6. Load test
7. Insulation test.
Type test is the test to be done for a new type of product. They are:
1. Lightning shock test
2. Local discharge test
3. Sudden short circuit test.
Dry transformers rely on air convection for cooling, and are generally used for local lighting and electronic lines. Dry-type transformers are widely used in local lighting, high-rise buildings, airports, wharves CNC mechanical equipment and other places. Simply speaking, dry-type transformers refer to the transformers whose iron core and windings are not impregnation in insulating oil. Cooling methods can be divided into natural air cooling (AN) and forced air cooling (AF). In the case of natural air cooling, the transformer can run continuously for a long time under the rated capacity. Forced air cooling, transformer output capacity can be increased by 50%. Suitable for intermittent overload operation, or emergency overload operation; Due to the large increase of load loss and impedance voltage during overload, it is in non-economic operation state, so it should not be kept in continuous overload operation for a long time.
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