Do varistors need safety certification?

As the core component of circuit protection, the safety certification requirements of varistors need to be comprehensively judged based on application scenarios, installation locations, and sales markets. The following is a specific analysis:
1、 Scenarios that require safety certification

Used for power input level protection

Varistors used at the input end of AC/DC power supplies (such as household appliances and chargers) must pass safety certification.
Reason: Directly subjected to power grid surges, failure may cause fire or electric shock risks.
Typical certifications: UL (North America), CQC (China), TUV (European Union).

Spanning between input and protective ground

When a varistor is connected between the phase line (L/N) and the protective earth (PE), special safety regulations must be met:
Austria, Belgium and other European countries prohibit the use of voltage sensitive resistors between the input and protective ground of plug-in power supplies.
If it must be used, it needs to be designed with enhanced insulation or double isolation.

As a lightning protection device

In the lightning protection modules of communication base stations, photovoltaic inverters, and other equipment, varistors must be certified through surge testing (such as IEC 61051-2).
2、 Mainstream safety certification standards
Certification type applicable to market core testing requirements representative standards
UL certification for North American withstand voltage testing, leakage current, and impulse current tolerance UL 1449
CQC certification for China's pressure-sensitive voltage, pulse current, and flame retardant performance (GB/T 10194) GB/T 10193-1997
TUV certification EU electrical safety, environmental reliability (such as Double 85 testing) IEC 61051-2
VDE certification for long-term stability and aging characteristics verification of high-end markets in Germany and Europe ENEC 10
Note: Surface mount varistors (such as 3225/4032 packages) need to be certified separately according to the package size.
3、 The core project of safety testing

Electrical performance

Voltage deviation of varistor: allowable deviation ± 10% (such as 470V ± 47V for 7S471K).
Leakage current:<100 μ A is required at 75% varistor voltage.
Residual voltage ratio: The ratio of residual voltage to varistor voltage under 8/20 μ s pulse current (the lower the better).

reliability verification

Pulse current withstand: withstand at least 2 waves of 8/20 μ s waveform impact (e.g. 7S series requires 1200A test).
High temperature and high humidity test: Verify moisture resistance in an environment of 85 ℃/85% RH (plastic encapsulated patch varistors must pass).
Flame retardant rating: The packaging material must meet the UL94-V0 fire protection standard.

Long term safety

Aging test: After multiple impacts, the drift of the pressure-sensitive voltage should be less than ± 10%.
Failure mode verification: Do not ignite during short circuit (through needle flame test).
4、 Special circumstances that do not require authentication

Low voltage signal line protection

Varistors used for signal ports below DC 24V (such as sensor interfaces) do not require mandatory certification if there is no safety risk.

Non safety critical locations

When the non isolated area inside the circuit board (such as IC power decoupling) does not involve personal safety, the enterprise can control the quality on its own.
The safety certification of varistors is not absolutely mandatory, but the following scenarios must be certified:
Power input stage (involving electric shock risk);
Lightning protection system (for high-energy impact scenarios);
Sell to specific markets (such as UL for North America and TUV for the European Union).
When selecting, priority should be given to products with UL/CQC/TUV certification (such as the Konigsegg 7S series), and strict matching should be made with the electrical parameters and safety levels of the application scenarios.