Handheld power tool knowledge - 1 views
started by kbojezhang44 on 01 Jun 20
started by kbojezhang44 on 01 Jun 20
started by kbojezhang44 on 01 Jun 20
started by kbojezhang44 on 01 Jun 20
1. Classification of handheld power tools
Hand-held electric tools can be divided into the following three categories according to electric shock protection:
(1) Class I tools. The tool not only relies on basic insulation for protection against electric shock, but it also contains an additional safety precaution.
(2) Class II tools. The tool not only relies on basic insulation in terms of protection against electric shock, but it also provides additional safety precautions such as double insulation or reinforced insulation. There are no protective grounding measures and no installation conditions.
(3) Class III tools. The tool is protected against electric shock by relying on the power supply from a safe voltage and no higher voltage than the safe voltage is generated inside the tool.
2. Requirements for the safe use of hand-held power tools
(1) Class I or class II hand-held power tools can be used in general locations with air humidity less than 75%. The rated leakage operating current of the leakage protector in the relevant switch box should not be greater than 15mA, and the rated operating time should not be greater than 0.1s.
(2) When operating in a humid place or on a metal frame, you must choose a Class II or Class II hand-held power tool powered by a safety isolation transformer.
(3) Class III hand-held power tools powered by safety isolation transformers must be selected in narrow places. The switch box and safety isolation transformers should be installed outside the narrow places and connected to PE lines. During operation, there should be someone outside to supervise.
Electric shock protection of hand-held power tools can be divided into 3 categories, and various types of hand-held power tools have different installation requirements for additional safety measures. Among the following statements about the connection of hand-held power tools to the protective earth, the correct one is ().
Class A.I equipment can be installed with or without protective earth
B. Class I equipment is not allowed to be connected to protective ground
C. Class III equipment must be connected to protective ground
D. Class III equipment does not need to be connected to protective ground
『Correct Answer』 D
『Answer Analysis』 Classification of handheld power tools:
(1) Class I tools. The tool not only relies on basic insulation for protection against electric shock, but also contains an additional safety precaution.
(2) Class II tools. In terms of protection against electric shock, the tool not only relies on basic insulation, but also provides additional safety precautions such as double insulation or reinforced insulation. It has protective grounding measures and does not depend on installation conditions.
(3) Class III tools. The tool relies on safe voltage power supply for preventing electric shock and protection and no voltage higher than the safe voltage will be generated inside the tool.