During the production process, the single-head electric heating pipe must go through the pressure pipe (compress the pipe diameter to the diameter required by the customer), high and low temperature barbecue, and also need to undergo pressure resistance test after completion. But all three steps change the resistance value of the heating tube, and of course the power will also change.
Please explain why this is happening?
Single-head electric heating tube: the iron pipe is wrapped with a magnesium rod wrapped around the resistance wire, the iron tube and the magnesium rod are filled with magnesia, and two iron wires connect the resistance wire to the outside of the tube as two poles. Magnesium rod is very hard and brittle, can be understood as chalk, so magnesium rod together with resistance wire will not become longer.
The power (resistance value) of the electric heating tube depends on the heating wire inside the electric heating tube. First, when your electric heating pipe passes through the pressure pipe (compressing the pipe diameter to the diameter required by the customer), the length of the electric heating pipe will inevitably increase, and the heating wire inside will also be lengthened, and the resistance value will change accordingly. Second, high and low temperature burning. The correction coefficient of the heating wire is not the same at a certain temperature, which will also lead to a change in the resistance value. As for the change of the third withstand voltage sense resistor value, it is not normal, which is to detect the electric heating tube. The withstand voltage test is only to detect whether its creepage distance has met the requirements, which has nothing to do with the heating wire.
Addendum: Is the electric heating tube extended? The electric heating tube is lengthened by the pressure tube, but the inside remains unchanged. That's a bit of a no-brainer. I really don't believe that if you have the conditions, you can dissect one and see.
