When it comes to power resistors, your options are many in this day and age. One of the oldest types of resistors that are still utilized today are wirewound resistors. The construction of all kinds of wirewound resistors is more or less the same. To create this resistor, you require an insulating material and wind a metallic wire around its core. Though they are created similarly, each type of wirewound resistor has different applications. There are basically two kinds of wirewound resistors. These are precision wirewound resistors and power wirewound resistors. Again, each of these resistors has their own functions. They can be used for current and temperature sensors.
The use of precision wirewound resistors is often common in measuring bridges and in accurate calibration devices. Under one-tenth percent should be the tolerance of these very accurate resistors. Unlike most metal film resistors that have a 25 ppm/C temperature coefficient, precision wirewound resistors have a 5 ppm/C temperature coefficient, which is better. With values such as 30 ppm, their stability is fairly good for twelve months of alteration and functioning at full power rating. This is the kind of wirewound resistor that you need if you will be requiring temperature increases below 30C. When you look at these wirewound resistors, they are coated by epoxy materials for this reason alone.
Power wirewound resistors are the second kind of wirewound resistor. These wirewound resistors have a power range between 0.5 watts and 1000 watts. If you want to break down these power resistors by kind, you have to do so according to their coating type. For purposes that require the lowest dissipation ranges, silicone resins are the most common. They are known for being small resistors and can withstand temperature increases to a maximum of 300C above normal levels. A porcelain enamel coat is another kind of coating for power wirewound resistors. It is only at low temperatures that this coating type will be able to offer good insulation properties. Once the temperature goes higher, the insulation will go down. This is why they are not so common in terms of power resistors. This type of coating can operate at maximum temperatures of only 400 degrees. In terms of resistance values, they are between 0.1 and 10 kOhm.
You have another coating type for power wirewound resistors, and they are ceramic coating. This is considered as the standard type of power wirewound resistors. To protect the wire, they come with a ceramic coating and core. When it comes to this coating, it can maintain good insulation properties while ensuring to have effective energy dissipation. Moreover, you get good physical protection with it. Their power ratings range between 5 and 18 watts. Even while warming up around three hundred degrees, this resistor will not have any problems at this range. Their resistance falls within the range of 10 and 20 kOhm.