Getting to Know Wirewound Resistors
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. All wirewound resistors are created similarly. Around the core of an insulating material, a metallic wire will then be winded. Despite the fact that they are created in the same manner, you can expect variations in the application of the different types of resistors. Wirewound resistors can be classified into two accordingly. These two are precision wirewound resistors and power wirewound resistors. All of them can be used for a wide array of applications. Some of the most common applications to them include the use in current and temperature sensors.
The most common uses of precision wirewound resistors include measuring bridges and accurate calibration devices. Since these resistors are very accurate, their tolerance levels should be under one-tenth percent. Their temperature coefficient is about 5 ppm/C, and this is always better than what most metal film resistors can give you which is about 25 ppm/C. In terms of stability, these wirewound resistors are fairly good with values like 30 ppm alternating for twelve months upon functioning with the use of full power. This type of wirewound resistor is often made for temperature increases that is just below 30C. Epoxy materials are often used as coating because of this reason.
For the other type of wirewound resistor, you call them power wirewound resistors. Between 0.5 watts and 1000 watts is the range of power of these wirewound resistors. If you want to break down these power resistors by kind, you have to do so according to their coating type. When the lowest dissipation ranges, you have to go with silicone resins. They are known for being small resistors and can withstand temperature increases to a maximum of 300C above normal levels. Another kind of power wirewound resistors is the one that has a porcelain enamel coat. This is a coating type that provides good insulation properties when there are low temperatures. You can expect the insulation to be less when the temperature goes up. That is why this makes these resistors less common. 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.
Another coating type for power wirewound resistors is ceramic coating. This is one of the most common types 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. You have a power rating from 5 to 18 watts for this kind of resistor. Without any problem, this kind of resistor can warm up around three hundred degrees. In terms of resistance, you can expect them to be between 10 and 20 kOhm.