ELECTRICAL PARAMETERS

Resistance Values

Whilst E24 values are preferred, other values are readily available at no additional cost.

Resistance Tolerance

20%, 10% and 5% available as standard.

Resistivity Range - ρ

3 Ohm cm to 30000 Ohm cm

ρ = R x A/L,   where R = Resistance Value

Temperature Coefficient - TCR

-0.05% to -0.15% per C Temperature Rise depending on Resistivity Value.

TCR = 0.16 x e -(log ρ / 1.4) - 0.135     (% / C Temperature Rise)

Voltage Coefficient - VCR

-0.5% to -7.5% / kV / cm

VCR = -0.62 x ρ 0.22   (% / kV / cm)

For ρ domain 10 to 7500 Ohm cm

Inductance

This is negligible (nH) and the resistors may be described as non-inductive. In practice the inductance of connecting leads will be greater than that of the resistors.

Dielectric Constant (Permittivity) εr

This is very difficult to measure and will vary according to material resistivity.

As an order of merit :     єr  ≈  5

Maximum Working Voltage Withstand per cm of Disc Length (V wk)

Volts

(rms)

SF6 V wk = 1.00 x (R/t x A/L) 0.335 kV/cm } t Domain 10 to 50 ms  
AIR V wk = .87 x (R/t x A/L) 0.3 kV / cm t = Insertion time in ms

 

         

ρ Domain 10

to 7500 Ohm cm

Volts (Impulse)

SF6 V wk = 8.0 x 1.2 √ Log (R/2.54 x A/L) kV / cm   1.2 / 50 s Waveform
AIR V wk = 4.3 x 1.2 √ Log (R/2.54 x A/L) kV / cm   1.2 / 50 s Waveform
AIR V wk = 3.0 x Log (R/2.54 x A/L) kV / cm   50 / 1000 s Waveform
AIR V wk = 1.5 x (Log (R/2.54 x A/L)) 1.25 kV / cm   100 / 10000 s Waveform
 
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
                     
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   Copyright HVR International Limited 2015. All Rights Reserved. This page last updated: 17 April, 2013.