Wirewound resistor

 
Wirewound resistor

What is a wire-wound resistor? A wire wound resistor is an electrical passive component that limits current. The resistive element exists out of an insulated metallic wire that is winded around a core of non-conductive material. The wire material has a high resistivity, and is usually made of an alloy such as Nickel-chromium (Nichrome) or a copper-nickel-manganese alloy called Manganin. Common core materials include ceramic, plastic and glass. Wire wound resistors are the oldest type of resistors that are still manufactured today. They can be produced very accurate, and have excellent properties for low resistance values and high power ratings. Definition of a wirewound resistor A wire wound resistor is a resistor where a wire with a high resistivity is wrapped around an insulating core to provide the resistance. Construction Wire wound resistor construction varies widely. The manufacturing and choice of materials used is dependent on the way the resistor will be used in a circuit. All are made by winding a wire around a core. The resistance value is dependent on the resistivity of the wire, the cross section and the length. Since these parameters can be accurately controlled, a high precision can be achieved. For high tolerance requirements, the resistance value is measured to determine exactly the cut to length of the wire. To create a high resistance, the wire diameter needs to be very small and the length very long. Therefore wire wound resistors are mainly produced for lower resistance values. For low power ratings, very thin wire is used. The handling of the wire is for this matter critical. Any damage may sever contact. After winding the wire is well protected from access of moisture to prevent electrolytic corrosion. Next to precision, there are also wire wound resistors with high power rating for 50W or more. [… read more]