doorbraakspanning

Doorbraakspanning is the maximum voltage that an insulating material, component, or structure can withstand before electrical breakdown occurs and the material becomes conductive. It is a fundamental parameter in the design of power insulation, cables, capacitors, transformers and semiconductor devices, indicating the voltage level at which insulation may fail.

Breakdown is highly dependent on the medium and geometry. In gases, breakdown manifests as a discharge (spark) when the electric field accelerates electrons enough to ionize molecules. In solid dielectrics and liquids, breakdown is a dielectric failure caused by excessive field leading to rapid current increase and possible permanent damage. In semiconductor devices, reverse breakdown can arise from Zener tunneling or avalanche multiplication.

The breakdown voltage is influenced by thickness, material quality, temperature, humidity, and mechanical stress. For a uniform field, the breakdown voltage roughly scales with thickness, and is often expressed as a dielectric strength in volts per unit length. Designers choose operating voltages well below the breakdown voltage to provide a safety margin.

Measurement and standards involve applying a controlled voltage ramp under specified environmental and electrical conditions until a defined leakage current or arcing is observed. Standards from IEC, ANSI and corresponding national bodies describe test setups and acceptance criteria for insulation systems and electrical components.

Typical numbers vary widely: air at room conditions has a dielectric strength around 3 MV/m; solid insulators range from about 1 to several tens of MV/m depending on the material and quality. In diodes, the term breakdown voltage denotes the reverse voltage where conduction begins, with Zener and avalanche mechanisms.