The AC03..CS safety resistors use specially selected resistive winding wire and special coating material to ensure safe and silent fusing operation in overload conditions. The resistor fuses “without a bang” when AC mains voltage is applied. At the same time, it acts as a in-rush current limiting resistor for the normal operation. The specially developed lacquer coating matches the thermal and electrical insulating properties of standard silicone cement. This allows designers to more easily meet the requirements of UL approval, whilst eliminating the need to put additional fuses in series with the input resistor.
In the conventional wirewound resistor, ceramic rod at the resistor's core acts as a heat sink for the wire element. This can delay fusing, resulting in high temperatures to fragment the coating and ionize the air near the fusing spot. If ionization occurs close to the cap edge and at a voltage peak in the mains cycle, it can initiate a momentary flashover outside the component body, releasing far more energy than is required to fuse the wire element. Although the opening of the circuit is safe for most applications, it can be with a “bang” with splattering of cement coating. This is un-safe operation and not desirable.
AC03 Safety resistor has new coating material and process to give silent and safe fusing. It can absorb thermal stresses without fragmenting or burning of resistor coating.