The difference between vlf hipot tester and ac series resonance test system

The main difference between ultra-low frequency withstand voltage and series resonance lies in their application scenarios, technical principles, and equipment composition.
Application scenario: The ultra-low frequency withstand voltage test is mainly used for the withstand voltage test of cables, especially for cables of 10kV/35kV specifications. The series resonance test device is widely used in industries such as power, metallurgy, petroleum, and chemical engineering, and is suitable for high-capacity, high-voltage capacitive test samples such as generators, power transformers, GIS, high cross-linking power cables, transformers, bushings, etc.
Technical principle: The ultra-low frequency withstand voltage test converts a 50 Hz AC voltage into a 0.1 Hz AC voltage for testing. This method is particularly effective for detecting insulation defects at the end of cables, as the capacitor current is greatly reduced at ultra-low frequencies, resulting in a higher voltage on the end insulation and facilitating defect detection. Series resonance utilizes the resonance principle of inductance and capacitance. When a circuit undergoes series resonance, the impedance in the circuit is minimized and the current reaches its maximum value. The series resonance test device consists of a variable frequency power supply, an excitation transformer, a reactor, and a capacitive voltage divider. By adjusting the output frequency of the variable frequency power supply, the circuit resonates, thereby generating a higher test voltage on the test sample.
Equipment composition: The ultra-low frequency withstand voltage test device mainly includes a high-voltage transformer and a voltage doubling circuit. Through these devices, 50 Hz AC voltage is converted into 0.1 Hz AC voltage for testing. The series resonance test device includes a variable frequency power supply, excitation transformer, reactor, and capacitive voltage divider, which are used to measure the resonance voltage on the test object and provide overvoltage protection signals.
In summary, there are significant differences between ultra-low frequency withstand voltage and series resonance in application scenarios, technical principles, and equipment composition. Ultra low frequency withstand voltage is mainly used for detecting insulation defects at the end of cables, while series resonance is suitable for withstand voltage testing of high-capacity, high-voltage capacitive specimens.