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Why doesn’t the electric welding machine have such a high current?

Why doesn’t the electric welding machine have such a high current?
Electric welding machine is a transformer. The product of primary voltage and current is equal to the product of secondary voltage and current. Electric welding machine is a step-down transformer. In order to melt the welding rod, a large current must be used. As the current increases, the voltage decreases. Not hurting people is the reason for the low voltage. The human body has a certain resistance and low voltage, and the current passing through the human body is small, so it will not electrify people.

电焊机电流那么大为什么不电人?

But it cannot be said that the electric welding machine will never hurt people. If people stand in the water, they will still hurt people, because the humidity reduces the resistance of the human body and the current increases. The voltage below 12 volts will not hurt people. The safety current that the human body can withstand is very small, only about 10mA. If the current is greater than 10mA, there will be obvious sensations, such as paralysis, tingling, and difficulty breathing. If the current is greater than 50mA, there will be a risk of electric shock. When the current is greater than 100mA, The human body will suffer from breathing difficulties, cardiac arrest, coma, etc. It can be seen that the human heart is very fragile.

电焊机电流那么大为什么不电人?

Since the current that the human body can withstand is so fragile, why doesn’t the electric welding machine have such a high working current? First of all, we must understand the relationship between voltage, current, and current loop.

(1) The current when the electric welding machine is working is indeed very large, generally more than hundreds of amperes, but this current loop only flows from the positive electrode to the negative electrode of the electric welding machine, and does not pass through the human body. Connected to the negative electrode), the current loop of hundreds of amperes is: welding tongs → welding rod → welding parts → grounding clamp, from the grounding clamp to the internal negative electrode of the welding machine, and does not pass through the human body! Therefore, no matter how large the current is, it will not cause harm to the human body!

电焊机电流那么大为什么不电人?

(2) The average resistance of the human body is about 2000Ω. If the hand of the human body touches the welding clamp (positive electrode) and the foot touches the welding piece (negative electrode), then the current flowing through the human body is another circuit (not between the welding rod and the welding piece). According to Ohm’s law I=U/R, the normal operating voltage of the electric welding machine is about 30V~45V, and the average resistance of the human body is R=2000Ω. The human body current is 15mA~22.5mA. Feeling numb, it will not be life-threatening.

电焊机电流那么大为什么不电人?

(3) According to industry regulations, the safety voltage of the human body does not exceed 36V, the no-load voltage of the electric welding machine can reach 70V, and the working voltage is 30V~45V. Therefore, the electric welding machine is not without danger. The human body current greater than 50mA may be life-threatening. It can be reversed. If calculated by no-load 70V, R=U/I=70V/50mA=1400Ω, which means that when the resistance of the human body is less than 1400Ω, there will be a risk of electric shock, and the resistance of the human body is related to the human physique and skin surface. The degree of dryness is related. When the resistance of the human body is mainly concentrated on the surface of the skin, when the skin is wet, the resistance of the human body will be greatly reduced. When the skin sweats, the resistance of the human body will drop to about 1000Ω, so there is still a risk of electric shock if you do not pay attention to electric welding. Therefore, the shell of the welding station must be connected to the ground, and the welding must be carried out in a dry environment. Wear safety insulating shoes, insulating gloves, etc.

 
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