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Silicon Carbide Varistors - Zinc Oxide MOV’s

SiC Disk Varistors | SiC Rod and Tube Varistors | MOV / Zinc Oxide (ZnO) Varistor  | Silicon Carbide Varistors with Leads | Si-Metal Ceramic Composite Resistors ZnO Block Varistors

About Silicon Carbide Varistors

Our Silicon carbide varistors are made from about 90% silicon carbide of different grain sizes and 10% ceramic binder and additives. The raw material is formed into various varistors geometric dimensions and then sintered under specific atmospheric and ambient conditions at a high temperature.

A layer of brass is then flame sprayed on as an electrical contact. Other standard metallized contacts include Aluminum, Copper, Nickel and Silver. In the case of disks, an electrical connection is created by clamping a metal plate to each side of the disk using tie rod. Large assemblies in the case of disks are fashioned using metal plates with tab connections on each side of these disks to create series and parallel stacks of disks to provide appropriate overvoltage protection for high power. Smaller disks simply have tinned copper wires soldered to the brass layer and can be further processed to include a dielectric coating.

Geometries are manufactured to suite the electric values required by varying the OD, ID, thickness and length. Our manufacturing process yields good voltage dependences and high energy absorption.

Key features of Silicon Carbide Varistors

  • Self-Healing.
  • Used in Air/ Oil/ SF6 Environments.
  • Configurable into Single or Modular Assemblies.
  • Extremely High Ampacity.
  • High Surge Energy Rating.
  • 100% Active Material.
  • Repeatable Non-Linear Characteristic.
  • High Voltage Withstand.
  • Essentially Non-Inductive.

SiC Disk Varistors

Below is a list of our standard diameter disks 37, 45, 60, 80, 95, and 150mm: Energy absorption per disk ranges up to 122,290J allowing disk assemblies with extremely high energy absorption ratings in the tens of Mega-Joules.

Mechanical Parameters




Outside Diameter


37 to 150 mm

Inside Diameter


10 to 30 mm



2 to 25 mm

SiC Disk Dimensional Diagram

Standard Disk Specifications

Disk Size Characteristic Curves Disk Specifications
37mm OD Disk 37mm U/I Curves 37mm Chart
45mm OD Disk 45mm U/I Curves 45mm Chart
60mm OD Disk 60mm U/I Curves 60mm Chart
80mm OD Disk 80mm U/I Curves 80mm Chart
95mm OD Disk 95mm U/I Curves 95mm Chart
150mm OD Disk 150mm U/I Curves 150mm Chart

Electrical Parameters

Item Range
Operating Temperature Range -40 to 150°C
TCV (Typical Temperature Coefficient of Voltage) -0.12 to 0.18 %/°C
TCI (Typical Temperature Coefficient Current) 0.5 to 0.8 %/°C
Specific Heat Capacity Approximately 2 J/cm³/°C
Thermal Conductivity 0.07 W/cm² . °C/cm
Inductance nH’s (non-inductive)

SiC Disk Applications

  • Mains overvoltage from lightning, inductive or capacitive coupling.
  • Switch contacts with inductive load.
  • High switch-off voltages in transformers, motor and generator windings and magnet coils.

Rod and Tube Silicon Carbide Varistors

These Non-linear resistors Varistors are made from SiC and have high power dissipation and high energy absorption. This series is manufactured in rods and tubes with Outside Diameters ranging from 6 to 30mm and lengths up to 600mm. The Non-linear Resistors may be connected in series or parallel for various fields of application. Brass is the standard metallization, but these are also available in aluminum, copper and zinc. They can operate up to 150C continuously and have essentially zero inductance.

Mechanical Parameters

Description Abbreviation Range
Outside Diameter Do 6 to 30 mm
Inside Diameter Di 0 to 8 mm 
Length L 50 to 600 mm
Density N/A 1.9 g / cm³ to 2.0 g / cm³

Electrical Parameters

Item Range
Operating Temperature Range -40 to 150°C
Ohmic Range 500 to 17 x 106 Ω/cm
Maximum Pulse Residual Voltage 4.3 x 1.2√(log(R x A x l)) kV/cm
Specific Heat Capacity Approximately 2 J/cm³/°C
Inductance nH’s (non-inductive)

Rod and Tube Technical Specifications

Outside Diameter (mm) Inside Diameter (mm) Maximum Length (mm) Material Type Maximum Volume (cm3) Maximum Watts @ 20°C Maximum Joules @ 20°C (1) Tau (s)
6.7 0 200 6770 42.1 38.6 1290 45
25 0 600 64 471.2 301.3 66714 221
30 0 600 64 565.5 361.5 96068 266

Rod Material Specification – Outside Diameter 30mm x length 300mm

Maximum Length (mm) Maximum Volume (cm3) Material Type Maximum Watts@ 20°C Maximum Joules @ 20°C Tau (s) Heat Capacity (J/ (kg x K) Thermal conductivity (W/ cm² x K) Temperature coefficient (1/K)
300 2120.6 6770 259.3 51718 199 856 0.00611 -2.85E-04
300 2120.6 64 180.8 48034 266 917 0.00492 -1.84E-04
300 2120.6 82 226.7 323 1.4 6 0.00617 -1.05E-10


MOV / ZnO Varistors with leads

We offer a large range of radial leaded disk metal-oxide varistors (MOV) manufactured with 90% of ZnO. These range from voltage up to 1100VDC and Maximum Energy Absorption of 230 Joules. Radial leaded disks come in diameters of: 5 mm, 7 mm, 10 mm, 14 mm and 20 mm.

List of standard values

Series Disk Size Specification Chart
5M 5mm 5M - Chart
7M 7mm 7M - Chart
10M 10mm 10M - Chart
14 M 14mm 14M - Chart
20 M 20mm 20M - Chart


ZnO Block Varistors

ZnO Block Varistor

These are high energy absorption industrial Metal-Oxide Varistors (MOVs) designed to provide surge protection in heavy industrial applications. They feature solid terminals for safe wire connections and a case providing complete electrical isolation from the MOV disk.

Our varistors block package features superior creepage and clearance to minimize voltage breakdown along the package surface and providing complete electrical isolation of the MOV disk assembly.

List of standard values

Series Disk Size Specification Chart
40M 37mm 40M - Chart
60M 60mm 60M - Chart
80M 80mm 80M - Chart

Mechanical Layout

General Dimensions Block Varistor

Si-Metal Ceramic Composite Resistors

Si-Metal Ceramic Composite Resistors extend the operating temperature of ceramic resistors to a continuous rating of 350°C and Short derations rating of 390°C. This unique construction allows for the highest continuous power rating and high energy absorption. Failures occur at 600°C and above. Common geometries are rods and tubes with varying sizes. As with other composite resistors these may be connected in series or parallel for various total energy, electrical values and power ratings.

Si Metal Tube Resistor

Si-Metal Tube Resistor Specifications



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