Hand-held Power Tool Safety Technology

Hand-held power tools are divided into I, II, III class in accordance with security requirements.
Class I hand-held power tools rated voltage exceeds 50V, is non-secure voltage, It must be ground or zero for protection, but also must be connected leakage protection to ensure safety.
Class II hand-held power tools rated voltage exceeds 50V, but it uses double or reinforced insulation additional security measures. Double insulation means that  in addition to insulation work, as well as a protective insulating layer. When damage the insulation, operator isolate to charged body, it will not shock.
Class III hand-held power tools use safe voltage, it needs to have a good two-winding transformer isolated power supply, transformer rated voltage does not exceed 50V. So they is not necessary to connect ground, but be sure to install leakage protection.
Hand-held power tools must be installed isolation switch, short circuit protection, overload protection or leakage protection.