MECHANICAL PARAMETERS

Dimension Range

Outside Diameter (Do) 0.3 to 15.1 cm

Standard Length (L) 2.54 cm

Length (L) 1 to 5 cm

Density

Nominally 2.25 g / cm³

Shock and Vibration

Linear Disc Resistors are robust and capable of absorbing transmitted mechanical shock provided direct impact is avoided.

Coefficient of Linear Expansion

+ 4 x 10 ^-6 to + 10 x 10 ^-6 per °C

Youngs Modulus

3 x 10 ⁶ N cm ^-2

Bending Strength

30 to 60 kg.m for a 15.1cm dia. disc

Crushing Strength

Average value 12000 N cm ^-2

Assembly Mounting Force

Linear Disc Resistors may be assembled directly to the busbar or assembled into stacks by mounting on an appropriate tie rod. Sufficient assembly force must be maintained to provide good electrical interdisc contact over long periods of time. HVR recommend the use of several disc spring washers in series (reduces stiffness ratio) to provide the reliable mounting force described below:

Force (kg) = 120 x (Do - Di) ^0.7    (±50%)

As a guide the total compression (deflection), from 'just nip' condition should be:

Total Compression = 2 + (Number of Discs x 0.1) mm

Greater compressive forces are permissible provided  the disc contact surfaces are ground flat and are free from foreign bodies, thereby minimising the risk of destructive induced bending moments.

Disc Terminations

Metallised contacts are flame sprayed onto the opposing flat surfaces of the Resistor Discs. Standard metallised contacts include Aluminium, Copper , Brass, Nickel and Silver.

Anti-Track Coating

Epoxy and Silicone based anti-track coatings are utilised for improvement of dielectric withstand in Air and SF6 gas.

Environmental Protection

Resistor Discs can be impregnated with Silicone Varnish to reduce moisture ingress and terminals Electroless Nickel Plated to minimise corrosion.

Resistor Drying

Ceramic Resistors are porous and absorb moisture, this should be removed from the disc prior to use. Dry the discs in an oven at 110 - 120 °C for 24 hours. Place discs in a sealed container with silica gel.