Impedance matching of high frequency induction heating equipment

Generally speaking, impedance matching is to make the high-frequency induction heating equipment work in the best state and give full play to the best performance of the equipment. The power of the whole machine will eventually heat the workpiece through the inductor, so the heating effect of the workpiece is inseparable from the inductor. The heating effect of the workpiece not only depends on the working current of the inductor, but also is directly related to the shape of the inductor, the number of turns, the length of the lead copper tube, the material of the workpiece, the shape and other factors. The design of the inductor should generally follow the following principles:

1. The shape of the inductor should be determined according to the shape of the induction heating surface of the workpiece. The manufacturing principle should make the copper tube at the induction part parallel or equidistant from the workpiece surface and the current flow direction between adjacent turns should be consistent.

2. To determine the number of turns of the inductor, a double-turn or multi-turn structure should be used in the following situations:

A. Non-ferromagnetic materials such as copper, aluminum, etc.

B. Workpiece diameter ≥ 20mm

C. Plane heating

D. Heating with an external magnetic field

3. The principle of adjusting the gap between the sensor and the workpiece is as follows:

A. The gap between the small workpiece and the sensor should be controlled within 1-3mm.

B. The gap between the larger workpiece and the sensor is determined according to the following principles. When the power adjustment knob has been adjusted to the maximum, the current indication is also at the maximum but the heating speed is very slow. At this time, the gap between the workpiece and the sensor should be reduced or the sensor should be increased. number of turns. When the power adjustment knob is adjusted to the maximum but the current display does not reach half of the maximum current, the gap between the workpiece and the inductor should be increased or the number of turns of the inductor should be appropriately reduced.

4. For heating with an external magnetic field (such as plane heating, internal quenching of the workpiece, etc.) or heating of non-magnetic metals, different shapes of ferrite materials can be used to gather magnetism, which can greatly improve the heating efficiency of the equipment.

5. The lead-out length of the sensor should not be too long, which will increase the loss of equipment.

6. When the shape of the inductor is determined by the heating method and the heating efficiency is low, consider choosing high-power high-frequency induction heating equipment.

7. Production of sensors

A. The material is copper tube with a diameter of φ5 or more (thick wall is more than 1mm), and the copper tube with a diameter of more than 10mm is better to use a square copper tube.

B. Anneal the copper pipe first, then plug one end, and pour dry fine sand or lead liquid from the other end.

C. According to the shape of the designed sensor, it is gradually bent and beaten to shape. It is better to use a wooden or rubber hammer when knocking, so as not to damage the inner diameter of the copper pipe, resulting in poor water flow and damage.

D. After the bending is completed, tap the sensor with a copper pipe to shake out the fine sand. If the lead liquid is poured, the sensor should be heated until the lead is melted, and then all the lead liquid should be poured out to check whether the sensor is ventilated. For the inductor with multi-turn structure, in order to prevent the short circuit between the turns of the inductor, it should be covered with high temperature resistant insulating material (such as glass conduit or glass fiber tape, etc.), and the surface oxide layer should be polished clean on the electrical contact part connected to the machine.