The role of the excitation transformer in the AC Resonant Test System with Variable Frequency is to provide the excitation voltage required by the resonant circuit.In the AC Resonant Test System with Variable Frequency,the resonant circuit is usually composed of inductance$L$and capacitance$C$,while the excitation voltage$V_{text{exc}}$is provided by the excitation transformer.

　　The excitation transformer converts the input voltage into the required high voltage output to stimulate the resonant circuit to produce resonance.The transformation ratio of the excitation transformer determines the magnitude of the output voltage,which affects the working state of the resonant circuit.