• Maximum Overload Voltage of Resistor

The overload voltage of the resistor is the maximum value of voltage that can be applied to the resistor for a short time in the overload test.

Generally, the overload voltage of the resistor is 2.5 times the rated voltage. However, the voltage should not exceed the maximum overload voltage. The maximum overload voltage of the resistor is given in the data sheet.

The relationship between overload voltage and rated voltage is expressed by the following equation:

\begin{eqnarray}
\end{eqnarray}

The overload voltage and the maximum overload voltage are shown in red in the figure above.

The resistance value at which the overload voltage equals the maximum overload voltage is also called the critical resistance value.

If the resistance value of a resistor is less than the critical resistance value, the voltage can be applied up to the overload voltage, and if the resistance value of a resistor is greater than the critical resistance value, the voltage can be applied up to the maximum overload voltage.

In the data sheet shown above, the critical resistance value can be expressed by the following equation:

\begin{eqnarray}
\mbox{Critical Resistance Value}{\mathrm{[{\Omega}]}}&=&\frac{\left(\displaystyle\frac{\mbox{Maximum Overload Voltage}{\mathrm{[V]}}}{2.5}\right)^2}{\mbox{Rated Voltage}{\mathrm{[W]}}}\\
\\
&=&\frac{\left(\displaystyle\frac{600}{2.5}\right)^2}{0.25}\\
\\
&=&230.4{\mathrm{[k{\Omega}]}}
\end{eqnarray}

Supplement

• Resistors with low resistance values, such as shunt resistors, may not have a maximum operating voltage or maximum overload voltage listed because of their low rated voltage, which can be determined from the rated power.