Resistor Application

The purpose of applying varistors in different usage scenarios and the voltage/current stress acting on them are not the same, so the requirements for varistors are also different. It is important to distinguish these differences for correct use. According to the different purposes of use, varistors can be divided into two categories: protective varistors and circuit functional varistors.
Protective varistor
1. Distinguish between power supply protection, signal line protection, and data line protection using varistors, which must meet the requirements of different technical standards.
2. According to the different continuous working voltages applied to the varistors, they can be divided into two types: AC or DC for use across power lines. The aging characteristics of varistors under these two voltage stresses are different.
3. According to the different abnormal overvoltage characteristics borne by varistors, they can be divided into three types: surge suppression type, high-power type, and high-energy type.
Surge suppression type: refers to a varistor used to suppress transient overvoltage such as lightning overvoltage and switching overvoltage. The occurrence of this transient overvoltage is random and non periodic, and the peak value of current and voltage may be large. The vast majority of varistors belong to this category.
High power type: refers to a varistor used to absorb continuous pulse groups that occur periodically, such as a varistor connected in parallel to a switching power converter. Here, the impulse voltage period occurs, and the period is known. The energy value can generally be calculated, and the peak value of the voltage is not large. However, due to the high frequency of occurrence, its average power is quite large.
High energy type: refers to a voltage sensitive voltage regulator used to absorb magnetic energy in large inductance coils such as generator excitation coils and lifting electromagnet coils. For such applications, the main technical indicator is energy absorption capacity.
The protection function of varistors can be repeatedly applied in the vast majority of applications, but sometimes they are also made into one-time protective devices like current fuses. For example, a voltage sensitive resistor with short-circuit contacts connected in parallel to certain current transformer loads.