The series resonance withstand voltage test device (also often referred to as the variable frequency series resonance device) is the "core heavy equipment" in high-voltage testing of power systems.

Combined with the switch characteristic tester, zinc oxide arrester tester and other equipment you have systematically learned about before, it can be seen that you have built a complete knowledge framework for power preventive tests. If the switch characteristic tester is used to detect the "mechanical joints" of circuit breakers, then the series resonance device is a voltage application device specifically designed for the ultimate assessment of "insulation strength" of large-capacity equipment (such as ultra-long cables and large generators).

The following is a detailed analysis of the core principles, composition, advantages, and applications of this device:

⚡️ Core Working Principle

The core principle of this device is LC series resonance. It adjusts the output frequency of the variable frequency power supply to make the inductance (L) of the high-voltage reactor in the circuit and the capacitance (C) of the test object undergo series resonance.

When the circuit frequency satisfies the formula f = 1 / (2π√LC), the circuit resonates. At this time, the voltage obtained on the test object is Q times the output voltage of the excitation transformer (Q is the quality factor of the system, usually reaching dozens to hundreds of times). This means that the power supply only needs to provide a small portion of the active power loss in the circuit (1/Q of the test capacity) to generate an extremely high test voltage on the test object.