China's provisions of the safe voltage rating of the level of 42, 36, 24, 12, 6 volts. When the voltage used in electrical equipment exceeds the safe voltage, protective measures must be taken to prevent direct contact with the charged body as specified.
According to the characteristics of the production and workplace, the adoption of the appropriate level of safe voltage is a fundamental measure to prevent the occurrence of electric shock casualties.
The Safe Voltage (GB3805-83) is the most authoritative basic standard on the voltage that is not dangerous to human beings. Fully analyze the data in the table can be seen, in the most unfavorable conditions (in addition to medical and human body submerged in water), this limit is: 15 ~ 100Hz AC voltage (RMS) does not exceed 16v; no ripple DC is 35v.
Which 50Hz AC 16V value, compared to today's Chinese engineering habits (and even junior high school physics textbooks) is still used in the 36V, much lower; Even lower than the 1998 release of the GB4706.1-98 (household and similar appliances safety requirements of the general requirements of the safety of the special low voltage not exceeding 42V value.
Expanded information?The type of extra low voltage protection can be divided into the following three categories:
1. SELV. only as a safety extra low voltage protection for ungrounded systems.
2. PELV. Protection for safe extra low voltage only as protection for grounded systems.
3. FELV. For functional reasons (non-electrocution protection purposes), the use of extra-low voltage, but can not meet or is not necessary to meet all the conditions of the SELV and PELV. FELV protection is on this premise, supplemented by certain direct contact electric shock and indirect contact electric shock protection measures of a protection.
Baidu Encyclopedia-Safe Electric Voltage