Flux density units - Line/inch vs Tesla, Gauss 3

[electricpete]

What is the conversion between lines-per-inch and standard SI units (Tesla or Gauss)?

 

[cbarn24050]

Lines per inch? what are you talking about?

 

[dydt]

he is referring to (magnetic) flux lines per inch..

dydt

 

[electricpete]

I think it's lines per inch^2, not lines per inch (my mistake). These are the units used by motor shops when they talk about performing a loop test of a core. If we need to determine rated flux for purpose of loop test, they normally assume somewhere around 90,000 lines per inch^2. I think that may be around 14,000 gauss since that is where iron saturation begins on some textbook curves (depends on type of iron)... but I'm not sure exactly.

 

[cbarn24050]

Hi, I think you've sent this post out 13 days late.

 

[electricpete]

cbarn - no April fools joke here. Those lines per inch^2 are certainly not the units we learned in college, but those units are in my experience almost universally used in the the US motor repair business.

 

[electricpete]

cbarn... if you don't believe me, look up IEEE56-1977 (Inuslation Maintenance of Large Rotating AC Machinery), Appendix A (Test of Laminaor Insulation in Stator Cores)... list of symbols for Equation 2: "B - peak core-flux density in lines per square inch".

 

[jwerthman]

1 Gauss = 6.4516 lines/sq.in. (from CRC Handbook)

 

[electricpete]

Thanks JW. That is the number I was looking for.

 

[cbarn24050]

Ok, so whats the formula for working them out?

 

[Etrix]

Hello..

The definitions below gives 1 Gauss as 6.45 lines/in^2, just as JW says, and I've verified by calculation. Hope it helps.

Calculation:

From Definitions,
1 Max = 1 Line
since 1 Gauss = 1 Max/cm^2,

Simple conversion(1/cm^2 to 1/in^2) gives:

1 Gauss = 6.45lines/in^2

Definitions:

gauss (G or Gs) [1]
the CGS unit of magnetic flux density. A field of one gauss exerts, on a current-carrying conductor placed in the field, a force of 0.1 dyne per ampere of current per centimeter of conductor. One gauss represents a magnetic flux of one maxwell per square centimeter of cross-section perpendicular to the field. In SI units, one gauss equals 10-4 tesla. The unit is named for the German mathematician and astronomer Karl Friedrich Gauss (1777-1855).

maxwell (Mx)
a CGS unit of magnetic flux, equal to 10-8 weber. In a magnetic field of strength one gauss, one maxwell is the total flux across a surface of one square centimeter perpendicular to the field. This unit was formerly called the line [2]. The newer name honors the British physicist James Clerk Maxwell (1831-1879), who presented the unified theory of electromagnetism is 1864.

line (li) [2]
a former name for the maxwell, the CGS unit of magnetic flux. The unit was called the line because magnetic fields were traditionally represented by lines depicting the direction of the field; the idea was to quantify the strength of these lines. This is a small unit, so fields were often measured in megalines; one megaline is equal to 0.01 weber.

Definitions from this page:

http://www.unc.edu/~rowlett/units

Etrix

 

[electricpete]

Thanks Etrix. That takes some of the mystery out of those units.

 

[dydt]

good post and answers...

dydt

 

[jbartos]

Suggestion: It appears that Lines/cm**2 as a Gaussian unit of Quantity D=Electric Flux Density is convetible to Coulomb/m**2 as MKS unit as
1 x C/m**2 = [4 x (pi) x 10**(-5) / sqrt(muo x epsilono)] x Lines/cm**2
and
Gauss as a Gaussian Unit for B=Magnetic Flux Density is convetible to MKS unit Weber/m**2 as
1 Weber/m** = 10**4 x Gauss
Then obviously the Maxwell as a unit of PHI=Magnetic Flux is convertible to Weber as
1 Weber = 10**8 x Maxwell
By using Lines/cm**2 related to Maxwell, there is an ambiguity introduced in units, which may be viewed objectionable.
See Reference:
Table B2 "Conversion of MKS or International Units to Gaussian Units"
in
William J. Hyat, Jr., "Engineering Electromagnetics," Second Edition, McGraw-Hill Book Co., 1967
I see this as for example using tons for weight as well as for distance, which is possible but not practical and therefore not used.