ABSTRACT In recent years, the AC characteristics of metal oxide varistors have attracted growing research interest. This study presents an insulated‐gate bipolar transistor‐based device designed to address the limitations of existing power supply systems, which are unable to simultaneously maintain waveform stability and provide sufficient power when varistors operate in the non‐linear region. The proposed device generates a sinusoidal decaying oscillatory voltage waveform with adjustable amplitude and frequency, meeting the experimental requirements for varistors across a range of voltage levels and effectively extending the upper limit of the output current. Using this device, it is possible to capture the full dynamic response of leakage current, from capacitive to resistive behaviour, and to investigate the voltage‐sharing characteristics of varistor discs in surge arresters under AC excitation. Looking ahead, the device is expected to be applied to multiple tasks such as energy absorption evaluation of arresters/varistors, insulation tests of high‐voltage equipments and damped AC partial discharge detection of cables.