E-Field Breakdown: Realistic Values in Air & FR4

  • Thread starter Thread starter likephysics
  • Start date Start date
  • Tags Tags
    Break E-field
Click For Summary
SUMMARY

The realistic breakdown value for the electric field in air is commonly cited as 3 x 10^6 V/m in textbooks, while various online sources suggest a lower value of 1 x 10^6 V/m. The presence of dielectrics, such as FR4, increases the breakdown voltage, which can be calculated using the formula V=ε E*d, where ε represents the dielectric constant. Breakdown voltage is influenced by factors such as pressure, temperature, and humidity, with significant variations noted for different geometries like sharp points versus spheres. For those serious about high voltage applications, the book "Reference Data for Radio Engineers, fifth edition" is highly recommended for its comprehensive graphs on breakdown voltage.

PREREQUISITES
  • Understanding of electric field concepts and breakdown voltage
  • Familiarity with dielectric materials, specifically FR4
  • Knowledge of the Paschen Curve and its implications on breakdown voltage
  • Basic grasp of humidity's effect on electrical properties
NEXT STEPS
  • Research the Paschen Curve and its application in breakdown voltage calculations
  • Study the dielectric properties of FR4 and its impact on electrical insulation
  • Explore the "Reference Data for Radio Engineers, fifth edition" for detailed breakdown voltage graphs
  • Investigate UL standards related to breakdown voltage for specific products
USEFUL FOR

Electrical engineers, high voltage specialists, and product designers needing to understand breakdown voltage in air and dielectric materials like FR4.

likephysics
Messages
638
Reaction score
4
What is the realistic break down value for E field in air.
Text books say its 3*10^6 V/m
But there are many websites, which go down to 1*10^6 V/m.

If there is a dielectric like FR4, then the break down increases
V=ε E*d ?, where ε is the dielectric constant for FR4.
 
Engineering news on Phys.org
likephysics said:
What is the realistic break down value for E field in air.
Text books say its 3*10^6 V/m
But there are many websites, which go down to 1*10^6 V/m.

If there is a dielectric like FR4, then the break down increases
V=ε E*d ?, where ε is the dielectric constant for FR4.

It varies with pressure -- the relevant reference is the Paschen Curve:

http://en.wikipedia.org/wiki/Paschen_curve

(Click on the graph to enlarge it)
 
Assuming standard temp/pressure, is V=ε E*d valid ?
 
It depend on humidity also.
 
yungman said:
It depend on humidity also.

Yes! Given a constant humidity, is V=ε E*d valid ?
 
The book
Reference Data for Radio Engineers, fifth edition has a great graph for breakdown voltage.
If you are serious about working with high voltage, you should get this book.
Volts/mil breakdown voltage varies with spacing.
Breakdown voltage varies with pressure and temperature.
Breakdown voltage is different for sharp points and spheres.
Breakdown voltage varies only slightly with humidity unless there is condensation.
 
Carl Pugh said:
The book
Reference Data for Radio Engineers, fifth edition has a great graph for breakdown voltage.
If you are serious about working with high voltage, you should get this book.
Volts/mil breakdown voltage varies with spacing.
Breakdown voltage varies with pressure and temperature.
Breakdown voltage is different for sharp points and spheres.
Breakdown voltage varies only slightly with humidity unless there is condensation.

Thanks for the book suggestion. I will look it up.
I am not working with high voltage, but need the breakdown information.
Certain products need to meet standards set by UL (underwriter labs). Some of these standards are a mystery. Lot of ppl at work think breakdown voltage calculation(even under standard conditions) is some what blackmagic.
 

Similar threads

Replies
8
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
3
Views
2K