By hvhipot 
With the gradual expansion of power grid capacity, the capacity of AC withstand voltage testing equipment for large capacity high-voltage equipment is increasing. For example, the capacity of testing equipment often cannot meet the on-site testing requirements of conventional power frequency withstand voltage devices, so the AC withstand voltage test and partial discharge test of large capacity high-voltage equipment are widely used. The series resonance test equipment is widely used.
Series resonant devices are experimental devices that achieve resonance between series inductors and capacitors by adjusting their inductance or frequency; The series resonance test equipment adopts inductance regulation or frequency and voltage regulation methods. By using the principle of series resonance, 15-150 equivalent capacity tests can be completed with a small capacity power supply, greatly reducing the size of on-site test power supplies and equipment; The inductor series resonant device mainly consists of a control panel, a voltage regulator, an excitation transformer, a variable inductor, a capacitor frequency divider, etc.
By adjusting the gap between the iron cores of the series reactor, the inductance can be changed. When the inductance equals the capacitive reactance, the circuit resonates and becomes a pure resistor, resulting in a higher current and a higher voltage drop between the inductance and capacitive reactance; At this point, the power supply only provides active power, greatly reducing the size and weight of the testing device.
Variable frequency series resonant device
The variable frequency series resonant device mainly consists of a variable frequency power supply, excitation converter, reactor, capacitive voltage divider, etc; The variable frequency series resonant device converts the power supply into a frequency and voltage adjustable power supply through a variable frequency power supply. By adjusting the power frequency, the inductance equals the capacitance reactance, and the circuit generates series resonance, allowing the inductance or capacitance to obtain a voltage higher than Q times the excitation voltage. Due to good frequency regulation, the amplitude frequency characteristic curve of the circuit resonance is steeper, and the Q value of the circuit quality factor is higher.