# Why does dielectric strength decrease with thickness?

## Why does dielectric strength decrease with thickness?

Why does the dielectric strength (volts/mil) drop as the thickness of the Epoxy or urethane is increased. As a rule, the thicker the specimen under test, the lower the volts/mil results will be because the thicker sample will contain more impurities per unit volume.

What is the ratio of the breakdown voltage of an insulator to the thickness of the material?

Dielectric strength is calculated by dividing the breakdown voltage by the thickness of the sample. Most plastics have good dielectric strengths (in the order of 100 to 300 kV/cm).

What is the difference between dielectric strength and breakdown voltage?

The difference is important, since the breakdown voltage will be larger for thicker materials and smaller for thinner materials, but the dielectric strength will (theo- retically) remain unchanged. Dielectric strength is thus more like a material property, and breakdown voltage is more like a system property.

### What material needs the highest voltage breakdown?

A perfect vacuum has the highest theoretical intrinsic breakdown strength (over a trillion megavolts/meter).

• Dielectric materials with the highest breakdown strength include:
• Perfect Vacuum 1.3 x 10^12 MV/m.
• Diamond 2 x 10^3 MV/m (flawless film)
• Fused Silica 470–670 MV/m.
• Kapton H film 389–430 MV/m.
• What is a good dielectric strength?

It is defined as the maximum voltage required to produce a dielectric breakdown through the material and is expressed in terms of Volts per unit thickness. Most plastics have good dielectric strengths in the order of 10 to 30kV/mm.

At what voltage does air break down?

Although air is normally an excellent insulator, when stressed by a sufficiently high voltage (an electric field of about 3 x 106 V/m or 3 kV/mm), air can begin to break down, becoming partially conductive.

#### Why does thickness of insulation depend on voltage?

Material used in insulation have greater dielectric strength and absorbs all the voltage gradient just within few mm or cm distance. As voltage increases thickness of insulation increases. Thus insulation absorbs the voltage gradient.

What are the factors that affect the breakdown voltage?

The considered factors that affect the breakdown voltages are temperature, permittivity, tan δ, viscosity, velocity of the particles. The gap length is considered as 10mm and the factors are optimized around breakdown voltage of 50KV.

What has the highest breakdown strength?

High vacuum has the highest breakdown strength followed by thin homogeneous solids and then liquids.

## What do u mean by dielectric strength?

: the maximum intensity of electric field that a given dielectric can sustain without disruptive discharge, usually expressed in kilovolts per millimeter.

19/10/2020