Comparative tracking index

Example

Use in Lemonergy

Relate protection to faults, detection and response.

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Connected concepts

Related concepts from the knowledge graph. Connections show context, not cause and effect. Hover or focus a linked term for its definition.

Clearance

The shortest distance through air between two conductive parts at different potentials. It is sized for the highest transient voltage the insulation must withstand, since air breaks down at roughly 3 kV/mm, and must grow above 2000 m altitude where thinner air breaks down sooner. IEC 60664-1 sets the values for most electronics.

Creepage distance

The shortest path between two conductors measured along the surface of the insulation between them. Moisture and dirt on that surface can carry leakage current and tracking, so the required distance grows with working voltage, pollution and a poorer tracking index: at 400 V and pollution degree 2, basic insulation needs about 2 mm on a group I material but 4 mm on group III.

Electrical breakdown

The sudden failure of an insulator to block current once the electric field exceeds its dielectric strength, about 3 kV/mm for air at sea level and far higher for solid films. In 800 V drives, partial discharges in voids, driven by fast inverter switching edges, can erode insulation until it fails at normal voltage.

IEC 60112

The IEC test method behind the comparative tracking index (CTI) and proof tracking index (PTI) of solid insulating materials: drops of dilute ammonium chloride fall between two electrodes resting on the material until a conductive track forms. CTI is the highest voltage it survives for 50 drops and sets the material group used to size creepage distances; PTI confirms survival at one stated voltage.

Voltage class

The line between circuits that need high-voltage protection and those that do not. UN R100 calls a circuit high voltage above 60 V DC or 30 V AC rms, up to 1500 V DC or 1000 V AC; ISO 6469-3 calls the same band voltage class B and anything lower class A. A 48 V system stays below the line.

References & further reading

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

1. ISO 26262-1:2018 — Road vehicles — Functional safety — Part 1: Vocabulary

   International Organization for Standardization · 2018

   Topic background · Scope and terminology of automotive electrical/electronic functional safety. The catalogue is not the full standard.