Transistors – Getting Started & Next Steps

A Basic Guide to Wirewound Resistors

There are different types of power resistors that you can choose from in the market. Wirewound resistors are among the oldest types of resistors but are still used in the current market. Even if there are different kinds of wirewound resistors, they are created in more or less the same way. Usually, a metallic wire is winded around the center of an insulating material. Though its creation is similar across types, their areas of application are different. You can group wirewound resistors into two types. These are precision wirewound resistors and power wirewound resistors. The applications for these wirewound resistors are many. Some of the most common applications to them include the use in current and temperature sensors.

Some of the most common applications 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. 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. If you require a resistor for temperature increases below 30C, then this is the kind of resistor for you. 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. Between 0.5 watts and 1000 watts is the range of power of these wirewound resistors. To categorize these power resistors effectively, you have to look into their coating type. When the lowest dissipation ranges, you have to go with silicone resins. They can withstand temperature increases that are 300C above normal levels and are small resistors. Another kind of power wirewound resistors is the one that has a porcelain enamel coat. This kind of coating is widely used for providing good insulation properties at low temperatures. If the temperature goes up, the insulation will considerably be less. 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. If you talk about their resistance values, they are within 0.1 and 10 kOhm.

Ceramic coating is another kind of power wirewound resistors. This is one of the most common types of power wirewound resistors. To keep the wire protected from the resistor, the use of ceramic coating and core is expected. This coating provides an effective energy dissipation while still making sure that it has good insulation properties. Moreover, you get good physical protection with it. Their power ratings range between 5 and 18 watts. They can then warm up from three hundred degrees without difficulties. Speaking of resistance, the range is from 10 to 20 kOhm.

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