Carbon composition resistors (CCR) are fixed value resistors. These resistors are composed of fine carbon particles that are mixed with a binder such as clay and are usually baked to achieve a solid form. Today, CCRs are found in circuits and are made by the deposition of a metal or carbon film over a ceramic carrier.
CCRs are compatible with operations that require high energy pulses and their compact design makes them ideal for smaller applications. They can be used for surge or discharge protection, current limitations, high voltage power supplies, high power or strobe lighting, and welding. For example, CCRs are used for medical defibrillators and have the ability to withstand the high energy pulses of around 30 Joules that are emitted from the defibrillators.
Carbon composition resistors have many advantages, the biggest being their ability to withstand high energy pulses. As current flows through the resistor, its entire body conducts energy. Within a wirewound resistor, there is a smaller volume of wire to conduct current. In contrast, a CCR has a high thermal mass, resulting in a higher energy capability.
While CCRs are cost-effective, they do have a few disadvantages that cannot be overlooked. They have properties that are inferior in terms of temperature coefficient, noise pollution, voltage dependence, and load bearing capacity. CCRs were originally used in consumer electronics due to their low resistance value, making them unsuitable for high precision applications. Resistance values for this resistor can change up to 5% over the course of one year. With heavy use, the resistance may change up to 15%, and if used for soldering, it may cause a 2% change. This resistance instability is due to the CCR’s design.
The resistor is composed of materials with varying heat expansion properties. When the carbon particles and binder heat up or cool down, these changes impose stress in the resistor body. The contact between the carbon particles shifts, leading to changes in the resistance value as well. The noise generated by CCRs is very high due to the presence of different materials. As the current flows through the resistor, the noise level increases. Resistors of 0.25 W and 0.5 W can produce a maximum voltage of 150 V and 500 V, respectively.
The resistive materials used in CCRs are typically made of a blend of graphite, ceramic dust, and resin, which is then pressurized into sticks. The connecting wires are pressed into both ends of the resistor, and in some cases, metal caps are attached to the rod ends, forming the attachment for the wire leads. After a baking process, a massive resistive body is produced. However, when this process is utilized, it is difficult to predetermine resistance values within the resistor. Moreover, due to the resistor’s porous quality, keep in mind that a surface coating is required.
As resistors are integral to a myriad of industry applications, sourcing quality parts and components is of the utmost importance. Like most components in industrial equipment, smaller parts like bearings need to be repaired or replaced to ensure that your operations run smoothly. If you find yourself in need of carbon composite resistors, resistive materials, composite materials, or other related items, rely on ASAP Logistic Solutions.