Haefely 2830, User Manual, Page: 20 / 124

12 Theory
Series equivalent circuit
Series Equivalent
Circuit C
s
-R
s
Cs Cp
=  +
* ( tan *) 1
2

Rs Rp
= 
+
tan *
tan *
2
2
1


* measured values
5.3 The difference between Power Factor
and Dissipation Factor
While “Dissipation Factor”, tan

is used in Europe to describe dielectric losses, the calculation
used in the United States is
“Power Factor”, cos

.
The statistical data that have been collected in North America have been calculated using the loss
factor cos

(Power Factor) to specify the power losses in the insulation. Because the angles are
complimentary it is unimportant whether tan

or cos

is used as with very small values tan
 
0.5% the difference is negligible. However the conversion formulas are:


2
tan 1
tan
+
=
PF
2
1
tan
PF
PF
−
= 
5.4 Relative Permittivity
The linear permittivity of a material is usually given relative to
ε
0
the permittivity of free space
(vacuum permittivity), as a relative permittivity

r
(also called the dielectric constant). In a
anisotropic material, the relative permittivity maybe a tensor, causing birefringence. The actual
permittivity is then calculated by multiplying the relative permittivity by

0
.
0
  

=
r
to solve equations to

r
the below formula results.
0



=
r