First, the main equipment required for AC voltage test are:
Test transformer, voltage regulator and control equipment, voltage measuring device, protection resistance and protection ball gap, etc.
Ii. Precautions
(1) Before the AC voltage test, the external insulation surface of the tested product should be wiped clean, and the oil filled equipment should be stationary for a period of time according to the regulations to eliminate the possible residual air inside
(2) The AC voltage test is a destructive test, and the AC voltage test must be carried out after all the insulation test items have passed the test.
(3) In the process of voltage boost, the voltage rises slowly, and the current rises sharply, which may be due to the short circuit or similar short circuit of the tested equipment, or it may be caused by the large capacity of the tested equipment or near resonance
(4) In the voltage boost process, the current drops, the voltage is basically unchanged or has a downward trend, which may be due to the test load is too large, the power capacity is not enough, in the remote external power supply or the use of portable generators, especially should pay attention to this point.
(5) Most of the subjects connected to the test transformer are capacitive. During the AC voltage resistance test, the capacitive current generates a leakage resistance voltage drop on the winding, resulting in the actual voltage value acting on the subject exceeding the voltage value of the high voltage side calculated according to the variable ratio, resulting in a capacitance rise effect. Therefore, in the AC voltage withstand test of the subject with large capacitance, the test voltage should be measured directly at the end of the subject, so as to avoid the subject being subjected to too high voltage.
(6) The test transformer should generally be used within the specified rated voltage range, and avoid using the saturated part of the iron core.