1. We know that when a magnetic field is established, only reactive power needs to be fed from the power supply. Therefore, the current that generates a magnetic flux Φm is in phase with the magnetic flux Φm, and the phase of the backward voltage source voltage UA is 90º, which is called the magnetizing current, expressed by Iro, also known as the reactive component of the excitation current. The permeability μ of ferromagnetic materials is much larger than that of non-ferromagnetic materials, about several hundred times. Under the condition of alternating magnetization, there exists hysteresis phenomenon and hysteresis loss in the iron grid. The establishment of the magnetic flux Φm in addition to feeding reactive power from the power supply, also needs to feed active power to provide the active power required for hysteresis loss in the grid. Obviously, active power is only sent through a current that is in phase with the power supply UA. In addition, with alternating magnetic flux Φm, there is a large eddy current in the grid, and a large heat loss is also generated under the action of eddy current, that is, eddy current loss.

2. The current of hysteresis loss and eddy current loss in the grid is called the active component of the excitation current Ioa. The result of hysteresis and eddy current loss consumes the active power and is converted into heat energy in the grid. The grid is made of iron material, and the magnetic permeability μ is very large. In the process of magnetization, the magnetic domains in the ferromagnetic material are arranged according to the applied magnetic field. Due to the reciprocating oscillation of the magnetic domains, they encounter resistance between each other and consume a certain amount of energy. The energy lost in the form of heat due to hysteresis is hysteresis loss. The higher the frequency of alternating magnetization, the more hysteresis loss. It can be shown that the hysteresis loss is proportional to the frequency of the current used in magnetization, so the hysteresis loss in the grid is also lost in the form of heat. In addition, when the Φm of the alternating flux passes through the cross section of the grid, the induced current is generated on the cross section, and the heat loss is generated under the action of eddy current. Eddy current loss is proportional to the square of the current frequency in the reactor coil, and the grid is a closed loop composed of iron materials with strong magnetic permeability, so that the eddy current generated by Φm is also relatively large, that is, Ioa is relatively large. From IA=Ior+Ioa, it can be seen that when Ioa increases, if IA remains unchanged, Ior will decrease accordingly. In other words, in the excitation current IA=Ior+Ioa of the reactor, the active component increases and the reactive component decreases, which is very unfavorable for the substation, and the active component in the grid will be converted into a lot of heat.

3. We do not have a specific measurement of this active power component, but from the operation of the site, when the reactor is put into operation, the grid vibration, the bottom of the reactor insulator insulator connected to the ground wire vibration is relatively large (emit a large vibration sound), and the grid heat. The longer the reactor is invested, the hotter the grid, the lock of the grid door is hot, and the grid is hot. In response to the above situation, we replaced all the grids and used brick walls. In this way, it is not only economical, economical and beautiful, but also eliminates all the unfavorable factors analyzed above, which is safer and more reliable for people and equipment. The practical application proves that this is an effective and good method to ensure the safe and reliable operation of dry hollow reactor.