The series resonance test device and the test object capacitance C form a circuit in series



The series resonance test device, often referred to as the variable-frequency series resonance withstand voltage test device, is a core instrument in the power system for conducting AC withstand voltage tests on high-voltage, large-capacity equipment.

You can think of it as an "energy amplifier." It utilizes the principle of resonance between the inductance (L) and the test object capacitance (C) at a specific frequency, allowing a very small and lightweight power source to generate extremely high test voltages (such as several hundred kilovolts) across the test object. This completely solves the problem of traditional power-frequency test transformers being bulky and difficult to transport to the site.