Insulation resistance requirements for power tools
Release time: 2025-07-29
The insulation resistance requirements for power tools vary depending on the category: Class Ⅰ tools ≥2 MΩ, Class Ⅱ tools ≥7 MΩ, Class Ⅲ tools ≥1 MΩ (or 17 MΩ in special cases).
The insulation resistance requirements for power tools vary depending on the category: Class Ⅰ tools ≥2 MΩ, Class Ⅱ tools ≥7 MΩ, Class Ⅲ tools ≥1 MΩ (or 17 MΩ in special cases).
Insulation Resistance Classification Standards for Power Tools
Class Ⅰ Power Tools
Structural Features: Uses basic insulation + protective grounding design; relies on grounding the metal casing to prevent electric shock.
Insulation Resistance Requirements: No less than 2 MΩ, conforming to national standards such as GB 3883.1.
Class Ⅱ Power Tools
Structural Features: Features double insulation or reinforced insulation; does not require grounding protection.
Insulation Resistance Requirements: No less than 7 MΩ; higher resistance value is required due to the double insulation design to ensure safety.
Class Ⅲ Power Tools
Structural Features: Uses safety extra-low voltage (SELV, ≤50V); safety is ensured by the voltage itself.
Insulation Resistance Requirements: Usually ≥1 MΩ; may need to reach 17 MΩ in special cases (such as humid environments).
Testing and Precautions
Testing Method: Use a 500V or 1000V megohmmeter to measure; consider the influence of ambient temperature and humidity.
Safety Regulations: Insulation resistance is a core safety indicator. Even if the tool can operate normally, if the resistance does not meet the standard, there is still a risk of electric shock, which cannot be ignored.
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