Why not learn more about Transistors?

March 18, 2019


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A Basic Guide to 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. Even if there are different kinds of wirewound resistors, they are created in more or less the same way. To create this resistor, you require an insulating material and wind a metallic wire around its core. 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. You have precision wirewound resistors and power wirewound resistors. All of them can be used for a wide array of applications. They can be applied accordingly for current and temperature sensors.

Some of the most common applications of precision wirewound resistors include measuring bridges and accurate calibration devices. Under one-tenth percent should be the tolerance of these very accurate resistors. In terms of temperature coefficient, precision wirewound resistors are better with 5 ppm/C than with most metal film resistors with 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.

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 type of power wirewound resistors is coated with porcelain enamel. 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 one of the reasons why this kind of resistor is less common. 400 degrees is basically the maximum operating temperature for this type of coating. In terms of resistance values, they are between 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. When it comes to this coating, it can maintain good insulation properties while ensuring to have effective energy dissipation. In addition, it also offers good physical protection. The power rating for this resistor is between 5 and 18 watts. Even while warming up around three hundred degrees, this resistor will not have any problems at this range. Speaking of resistance, the range is from 10 to 20 kOhm.

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