What is the safety voltage? How many volts is the safe voltage? How does it come from? - Solution - Huaqiang Electronic Network

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In addition to the high voltage and low voltage voltages specified in the regulations, there is also a safety voltage. The so-called safety voltage is a voltage that is less harmful to personal safety than high voltage and low voltage. The voltage values ​​are typically 36 volts, 24 volts, and 12 volts.

In many different situations, the electrical resistance of the human body is also different. Generally, it is about 10,000-100,000 ohms (but also lower). If it is considered to be around 800 ohms, the experimental analysis shows that the power frequency limit current allowed by the human body is about 50 mA, which is 0.05 ampere. Under this premise, according to Ohm's law, it is known that the maximum limit power frequency voltage that the human body is allowed to withstand is about 40 volts. Therefore, generally take 36 volts as a safe voltage.

Even so, for those places with poor working conditions, that is, good electrical conductivity, low human body resistance, or where there are many metal containers such as cables in metal pipes, boilers, and underground tunnels, The safe voltage is set lower, usually taken as 12 volts. Therefore, 12 volts is often referred to as an absolute safe voltage in practice.

The regulations on safety voltage are not the same in each country. There are 50 volts or 40 volts, and 36 volts or 24 volts are also specified. The International Electrotechnical Commission stipulates that the limit of the contact voltage (equivalent to the safety voltage) is 50 volts, and when the voltage is less than 25 volts, safety measures against electric shock may be considered.