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Safety Protection Of Power Tools
- Aug 12, 2018 -

Ⅰ class: The tool is equipped with grounding device, the insulation structure of all or most parts of the basic insulation.  

If the insulation is damaged, as the accessible metal parts are connected with the protective grounding (see ground) or the protective 0 conductor installed in the fixed line through the grounding device, it will not become a charged body, which can prevent the operator from electric shock.

Ⅱ class: The insulating structure of such tools consists of double insulated or reinforced insulation consisting of basic insulation and additional insulation. When the basic insulation is damaged, the operator is separated from the charged body by additional insulation and is not electrocuted.   

The Ⅱ tool must be a non-re-connected power plug that does not allow grounding.

Ⅲ class: This type of tool is powered by a secure voltage supply. Between the safety voltage guide body or any one conductor and ground between the no-load voltage valid value is not more than 50V; for three-phase power supply, the no-load voltage between conductor and midline is not more than 29V. The safety voltage is usually supplied by a safety isolating transformer or a converter with independent windings.  

A protective grounding device is not allowed on the Ⅲ class tool.

Radio interference: Single-phase series motors with Commutator and DC motors will cause serious electromagnetic interference to TV sets and radios, so the power tools should consider the interference of the radio in the design. The main use of shielding, excitation winding symmetrical connection, set the electrical filter, filter to form and other measures. If necessary, a small inductance coil can be connected at both ends of the electric armature.