Comparative Tracking Index (CTI)
The Comparative Tracking Index (CTI) is an important metric in electrical engineering that evaluates the resistance of insulating materials to electrical discharges and breakdown behavior. The CTI is a unit of measure for the tracking and dielectric strength of insulating materials and is used as a benchmark for different materials.
The CTI is determined by a special test in which a voltage pulse is applied to a sample of the insulating material. The sample is then examined for its resistance to electrical discharges and breakdown behavior. The higher the CTI value, the more resistant the material is to this type of failure.
The CTI is important for the selection of insulation materials in electrical engineering as it ensures that the material meets the insulation strength requirements in various applications. Especially in high voltage and high humidity applications, such as in the automotive and aerospace industries, choosing the right insulating material is crucial.
It is important that the insulation materials meet the required CTI value to ensure safe operation of electrical systems. Using materials with a low CTI value can lead to insulation failure and create potentially dangerous electrical discharges that can result in damage to equipment or even personal injury.
Overall, the CTI is an important factor in the selection of insulation materials in electrical engineering and ensures that the insulation meets the insulation strength requirements in various applications.
Typical CTI values of some materials:
Phenolic resin: 125
Polyimide, Kapton: 150
FR4 (PCB base material, glass fiber reinforced epoxy resin): ≥ 175/250
FR4 Type KF: 400
PE-LD, PE-HD (polyethylene): 600
Polyester resin: 600
PTFE (polytetrafluoroethylene): 600
PBT (polybutylene terephthalate): 500
The CTI value is only standardized for voltages up to 600 V. For higher voltages, there is also the option of testing high-voltage tracking resistance.