ABSTRACT
Paper is an important dielectric material because its ready availability, low cost, mechanical and thermal properties make it ideal for use in capacitors.
Paper can be said to consist of a network of fibers and pockets either filled with air, water or oil depending on its treatment. To a first order approximation, the equivalent circuit consists of two capacitors C1 and C2 in series with leakage terms R1 and R2. For this model:
( )21' ωτ εε
εε +
−
In terms of the equivalent circuit,
RRC CRCR
+
+ =ε
+
−
CCC CC
o + =
∞ ε
11 RR CC
+
+ =τ
If testing is done over a reasonably high frequency range (>10 kHz) then the conductivity term σ is small and so
ε "'" −≈
Plotting ε"/ω vs ε' can be done by measuring R, C and tan δ as a function of frequency using a bridge circuit.
