The difference between the inner lead and the outer wiring of the single-head heating tube
From the point of view of the lead structure, the single-head heating tube is generally divided into an internal lead structure and an external structure, so what is the substantial difference between the two?
1. The production process is different
External wiring: the internal resistance wire is welded with the lead rod (hard lead rod or multi-stranded soft wire) and then lead out, and then connect the high temperature lead.
Inner lead: the high temperature lead is directly welded with the resistance wire and led out from the inside of the nozzle.
2. High temperature lead material is not the same
External wiring: Since the high-temperature lead is welded to the lead rod on the outside, the temperature of the welding part will not be too high at this time, and the high-temperature lead of the external wiring generally has a temperature resistance of 200 degrees.
Inner lead: Since the high temperature lead of the inner lead structure is directly welded to the resistance wire from the inside and inside the nozzle, the temperature resistance of the inner core of the high temperature lead of this structure must reach at least about 800 degrees. Generally, pure nickel wire is used. The cost is also high.
3. The creepage distance is different
From the perspective of creepage phenomenon, the inner lead is safer. The two lead rods of the external wiring are insulated and insulated with a glass fiber sheath. If the two leads accidentally expire, there will be a hidden danger of power connection.
4. Productivity
The production efficiency of the inner lead is far less than that of the outer wiring. The process of welding the inner lead with the resistance wire is relatively difficult, so generally the lead of the inner lead should not be too long.
5. Use angle
The inner lead wire is directly drawn from the inside of the nozzle, so the root lead is very flexible and can be bent at will.
Since the external wiring is connected to the lead after the lead rod is led out, the root cannot be bent at will.
If a lead wire rod is used, the root is very hard and cannot be bent; if multiple stranded wires are used as the lead wire and then connected to a high temperature lead, the root can be folded, but its flexibility cannot keep up with the inner lead. At the same time, due to the high temperature, it will be more twisted. The strand wire is generally stainless steel wire or iron wire, which is easy to become brittle at high temperature and easy to break if the bending frequency is high. The pure nickel wire of the inner lead does not have this problem.
