A metal oxide varistor (MOV) is a nonlinear resistor made from a sintered mixture of metal oxides. At a given temperature, its conductance rises rapidly as voltage increases. That is why it is also called a voltage-dependent resistor (VDR), and why it is widely used to limit or divert transient overvoltage in surge protection.
The formal definition
The IEC 61643-331:2020 definition, reproduced in IEC 61643-332:2024, reads: “non-linear resistor made of a sintered mixture of metal oxides whose conductance, at a given temperature, increases rapidly with voltage.” The standard adds that an MOV is “also known as a voltage dependant resistor (VDR).” The standard spells “dependant” that way. Most general writing uses “voltage-dependent.”
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Philips Support gives a plain-language version: “A Metal Oxide Varistor is a protective component that absorbs energy when a certain voltage is reached and dissipates that energy through heat.”
What “nonlinear” means here
An ordinary resistor keeps a constant ratio between voltage and current. An MOV does not. Under normal circuit voltage it conducts very little. As voltage climbs, its conductance increases steeply. In a protection circuit this gives surge current a path and limits the voltage across the protected equipment.
#1 Best Overall
- Littelfuse
- Intended Use: Industrial, Commercial and Automotive Use.
Two wording cautions apply. An MOV does not simply “block” every surge. It also does not hold voltage at one exact fixed level. The clamping level depends on the specific part and on the surge conditions.
What it is made of
Common MOVs are zinc-oxide based. TDK Electronics says its energy varistors are made mostly of zinc oxide. Panasonic describes its ZNR as a zinc-oxide non-linear resistor and says that product type is generally called a zinc oxide varistor or MOV. Panasonic dates the development of its ZNR to 1968. That is company product history, not the origin of all MOV technology.
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- Littelfuse
- Intended Use: Industrial, Commercial and Automotive Use.
What it is used for
IEEE classifies MOVs as surge protective components. Manufacturers such as TDK and Panasonic describe them as transient-voltage and surge-suppression parts. Consumer surge protectors, such as the Philips models covered by that support page, rely on them.
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Rank #3
- OEM: TVR10241V
- TVR10241V varistor is specially designed for surge protection. It can respond quickly and limit overvoltage, effectively protecting circuit safety
- 240V nominal voltage, 150V AC and 200V DC voltage are applicable, which can withstand high energy impact and ensure stable operation of the equipment
- Construction: Made from durable metal materials, this varistor offers excellent electrical conductivity and stability, ensuring long-lasting performance even in demanding environments.
- Wide Application Range: Ideal for home appliances and industrial devices, this varistor handles high-energy surges, making it essential for circuit protection in critical systems.
Key ratings
The IEEE Standards Association overview of IEEE C62.33-2016 (published January 29, 2018, shown as active) covers these parameter ranges. They describe what the standard spans. They are not the ratings of any single part.
| Parameter | Range in the IEEE C62.33-2016 overview |
|---|---|
| Nominal varistor voltage | 5 V to 1200 V |
| 8/20 surge-current rating | 10 A to 70 kA |
| 8/20 clamping voltage | 10 V to 3 kV |
The overview also lists package types, including leaded disc and surface-mount devices.
Rank #4
- This is a varistor (MOV) that protects electronic circuits from voltage spikes and surges by clamping excess voltage. Commonly used in power supplies, industrial controls, smart homes, and DIY projects, it safeguards sensitive components against transients caused by surges or power fluctuations, ensuring stable operation in AC/DC systems.
- Model: 14D201K; Varistor Voltage: 200V (180~220V range); Max. Allowable Circuit Voltage: AC 130V / DC 170V; Max. Clamping Voltage: 340V; Max. Surge Current (8/20μs): 6000A; Max. Energy Absorption: 70J; Reference Capacitance: 1000pF; Pin Type: Dual Straight Pins; Size: 14.5mm x 41.6mm / 0.57" x 1.64" (Dia. x L); Pin Spacing: 7.5mm / 0.3"; Package: 12Pcs Varistors
- The resistor is made of ZnO film, with a special epoxy resin coated disc structure with radial leads. It offers low loss, high operating voltage, excellent stability, stable capacitance, and high temperature resistance. Its compact design delivers high capacitance, excellent moisture resistance, and reliable overall performance.
- Connect the varistor in parallel across the circuit or component you wish to protect, such as across power input terminals. Ensure the pins are securely soldered to the PCB or terminals, requiring no manual activation.
- Select a varistor matching your circuit's working voltage and surge current requirements to maintain high impedance during normal operation. Ensure the operating voltage never exceeds its maximum rating. Avoid prolonged excessive voltage, replace if damaged or worn out, and store in a dry environment for reliable protection.
Varistor voltage is not clamping voltage
IEC 61643-332:2024 defines the two differently. Varistor voltage is measured across the MOV at a specified current, typically 1 mA. Clamping voltage is defined under specified class-current and waveform conditions. Compare ratings only when they were measured under the same stated conditions.
How to compare candidate MOVs
- Continuous circuit voltage compatibility
- Varistor (nominal) voltage
- Clamping voltage at the specified surge conditions
- Surge-current and energy capability
- Physical package
The right values depend on the circuit’s normal voltage and the surge conditions it must handle. The definition alone cannot identify a suitable part, so check the manufacturer’s datasheet for the exact model.
Quick Recap
Best Value
- This is a varistor (MOV) that protects electronic circuits from voltage spikes and surges by clamping excess voltage. Commonly used in power supplies, industrial controls, smart homes, and DIY projects, it safeguards sensitive components against transients caused by surges or power fluctuations, ensuring stable operation in AC/DC systems.
- Model: 10D681K; Varistor Voltage: 680V (612~748V range); Max. Allowable Circuit Voltage: AC 420V / DC 560V; Max. Clamping Voltage: 1120V; Max. Surge Current (8/20μs): 3500A; Max. Energy Absorption: 92J; Reference Capacitance: 130pF; Pin Type: Dual Straight Pins; Size: 10.5mm x 34.5mm / 0.41" x 1.36" (Dia. x L); Pin Spacing: 7.5mm / 0.3"; Package: 12Pcs Varistors
- The resistor is made of ZnO film, with a special epoxy resin coated disc structure with radial leads. It offers low loss, high operating voltage, excellent stability, stable capacitance, and high temperature resistance. Its compact design delivers high capacitance, excellent moisture resistance, and reliable overall performance.
- Connect the varistor in parallel across the circuit or component you wish to protect, such as across power input terminals. Ensure the pins are securely soldered to the PCB or terminals, requiring no manual activation.
- Select a varistor matching your circuit's working voltage and surge current requirements to maintain high impedance during normal operation. Ensure the operating voltage never exceeds its maximum rating. Avoid prolonged excessive voltage, replace if damaged or worn out, and store in a dry environment for reliable protection.
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