| 摘要 |
<p>The overvoltage preventing resistive system has voltage dependent NTC resistors (10) whose coefficient is fully or partly compensated by PTC resistive material (11). This compensation is provided by series connection of at least one PTC resistor. The voltage dependent resistors are made of a mixture of substances, one being a normal resistive material and the other one having a positive temperature coefficient. Preferably the different resistive material are mixed in such proportion that a considerable drop of resistive value occurs on exceeding of a given temp. threshold. Typically the voltage dependent resistors are made of zinc oxide and dopants, while titanium dioxide or a titanate are used for compensation of the temp. coefficients.</p> |
