Dielectric strength is a central characteristic in electrical engineering. It describes the maximum electric field strength that an insulating material can withstand before a breakdown occurs. The unit is kilovolts per millimetre (kV/mm).
What is dielectric strength?
Definition of dielectric strength
Dielectric strength indicates the maximum electric field strength that an insulating material can withstand before a breakdown occurs. It is measured in kV/mm and is a decisive criterion for the selection of insulating materials.
Properties of insulating materials
Key properties of insulating materials with regard to dielectric strength are:
- High electric field strength
- Low conductivity
- Thermal stability
How does temperature influence dielectric strength?
Higher temperatures increase the conductivity of a material and thus reduce its dielectric strength. Lower temperatures, conversely, improve the strength, since molecular ionization decreases. This relationship must be taken into account in particular when designing insulation systems for different operating temperatures.
How is dielectric strength measured?
Procedures for determining the breakdown voltage
Measurement is carried out by gradually increasing the voltage until a breakdown occurs. International standards such as IEC 60243 are observed to ensure comparable and reproducible results.
The role of electric fields in testing
Homogeneous electric fields ensure the accuracy of the measurement. Factors such as humidity and material purity influence the results and must be controlled.
Which factors influence dielectric strength?
Composition of the insulating material
Material purity and homogeneity increase dielectric strength. Contaminants and inhomogeneities act as weak points and reduce the strength.
Moisture and electric voltage
Moisture significantly reduces dielectric strength, since water increases the conductivity of the material. Higher voltages increase the probability of breakdown.
What are the applications of dielectric strength in electrical engineering?
Use of plastics in electrical applications
Materials such as polyimide, PTFE and polyester offer high dielectric strength together with flexibility and are excellently suited for electrical insulation.
The role in the technology of modern electrical devices
Dielectric strength plays a central role in capacitors, transformers and in circuit insulation of modern electronic devices.
Examples of materials with high dielectric strength
- Ceramics: High dielectric strength and thermal stability
- Glass: Excellent insulating properties and chemical resistance
- Polyimide and polycarbonate: Flexible plastics with excellent electrical properties
How does direct voltage differ from alternating voltage in terms of dielectric strength?
Direct voltage produces a constant electric field, whereas alternating voltage causes dynamic loads that can lead to more rapid material fatigue and earlier breakdown.
GOBA processes voltage-resistant insulation materials with high dielectric strength for electrical engineering applications.
GOBA Takeaway
Dielectric strength is a fundamental characteristic for the safety and functionality of electrical devices. The right choice of material, taking all influencing factors into account, is decisive for reliable insulation systems.