Varistors protect circuit functionality from risks posed by overvoltage events, preventing sudden voltage fluctuations from potentially damaging equipment. Evaluation of varistor performance involves a comprehensive set of parameters. These include nominal voltage, voltage ratio, maximum clamping voltage and residual voltage ratio, as well as rated and leakage currents, and the relationship of these parameters to temperature and voltage fluctuations.
At the heart of these specifications is the nominal voltage, which is a basic specification that represents the voltage level when a varistor experiences 1mA of DC current. This measure sets the voltage threshold and significantly affects the circuit design and varistor selection process. Describes the voltage operating boundaries within which the varistor operates, thus affecting the circuit architecture. To ensure enhanced protection and stability, the nominal voltage of the varistor must be consistent with the circuit's operating voltage.
Another key parameter, voltage ratio, reveals the voltage management efficiency of the varistor. It does this by juxtaposing voltages at 1mA and 0.1mA currents, giving engineers a baseline for evaluating varistor performance under different electrical loads. The maximum clamping voltage indicates the maximum voltage that the varistor can withstand and is the benchmark of its protection capability. The varistor selected must have a maximum clamping voltage above the highest expected voltage spike to guarantee complete protection.
In addition, the residual voltage ratio (comparing the residual voltage for a specific current to the nominal voltage) can provide insight into the effectiveness of the varistor in reducing circuit voltage during overvoltage conditions. Lower ratios protect delicate components from damage.