Shell-type transformers use an anti-พรั่ง coil with high dielectric strength to resist the influence of pulse แรงดันไฟฟ้า. Since shell-type transformers use coils with large surface area, the series capacitance between coils is large. When a พรั่ง is applied, it can Distributing the แรงดันไฟฟ้า reasonably, the surge coil is a non-oscillating winding, which can suppress the voltage oscillation caused by the pulse voltage.