Study On Air-core Reactor Wound By Large-Inductance Wire

With the rapid development of power systems, the number of demand for powerreactors in power system is greatly increased compared to earlier. Among them,dry-type air-core reactor has a simple structure, easy maintenance, long-term outdooroperation, no magnetic saturation, strong anti-short-circuit ability, etc, so it is widelyused. But, in order to meet the requirements of design values of inductance and heatdissipation, conventional air-core reactor’s volume is larger, and the power loss islarger, also electromagnetic radiation pollution and noise pollution caused byvibration are more serious to the surrounding environment; in addition, the analyticalcalculation method for air-core reactor inductance is more complicated.To solve these problems, the winding wire of the conventional air-core reactor isinnovated and improved: the magnetic particle layer is added outside of theconventional aluminum core by learning from large-inductance power cable patentedtechnology; the magnetic layer makes the inductance of wire increased greatly, thus itbecame a large-inductance wire. The windings of air-core reactor are wound withlarge-inductance wire alternative to conventional wire, and the number of staysbetween encapsulations is increased reasonably, so the air-core reactor wound bylarge-inductance wire is get. Secondly, the calculated method of air-core reactorinductance is innovated: the inductance of air-core reactor is calculated by finiteelement energy method, taking a practical conventional air-core reactor for example,and it is verified that this energy method is feasible. Finally the air-core reactorwound by large-inductance wire which has the same inductance with the actualconventional air-core reactor is designed by finite element method, and the two kindsof air-core reactor are made a comparative study.The study of this paper focuses on the following aspects:Firstly, classification of reactors and air-core reactor’s structural characteristics,trends and research status are introduced; inductance calculation methods of theair-core reactor are introduced in detail, then the advantages and disadvantages of thedifferent calculation methods are summarized and compared.Secondly, the analytical formulas of magnetic field, the EMF and inductance ofair-core reactor are derived; the traditional design approach of air-core reactor isbriefly described, and the field of application of the different design methods is summarized.Again, the numerical calculation, finite element analysis technique and theANSYS finite element software are overviewed briefly; the theory of the finiteelement energy method to calculate the air-core reactor inductance is analyzed indetail; taking a practical conventional air-core reactor for example, its inductance issolved by finite energy method, and it is verified that the energy method to calculatethe inductance of the air-core reactor is feasible by contrast to the actual inductancevalue.Then, the overall finite element design steps of the air-core reactor wound bylarge-inductance wire are given; the innovative structure and size selection of thelarge-inductance wire as well as the overall structure of air-core reactor wound bylarge-inductance wire are elaborated; and the calculated methods of initial number ofturns and temperature rise are given. The optimal finite element model is got byoptimizing air-core reactor wound by large-inductance wire.Finally, using ANSYS software, the three-dimensional finite element models ofthe air-core reactor wound by large-inductance wire and practical conventionalair-core reactor are established, and the electromagnetic field distribution, size of theinductance value, power loss and electromagnetic force distribution of both modelsare analyzed comparatively. The results show that: the air-core reactor wound bylarge-inductance wire has larger inductance, lower electromagnetic radiation pollution,lower power loss, lower electromagnetic force than that of the conventional; under thecondition of the same inductance, the volume of the air-core reactor wound bylarge-inductance wire is decreased by24.4%than that of the conventional air-corereactor, and the AC power loss is decreased by20.83%than that of the conventionalair-core reactor.The basic principles of modal analysis are introduced; using ANSYS software,the finite element modal models of encapsulation and stays of the air-core reactorwound by large-inductance wire and practical conventional air-core reactor areestablished, and these two models are made modal analyses comparatively. Theanalyses show that: the encapsulated winding vibration deformation is consistent tothe force distribution of the reactor windings; the modal frequency of the winding ofthe air-core reactor wound by large-inductance wire is greater than that ofconventional air-core reactor, so the possibility of resonance is less than that of theconventional air-core reactor; the magnitude of the five kinds of vibrations of air-corereactor wound by large-inductance wire are all less than that of the conventional air-core reactor, so the noise caused by vibration is significantly lower than that of theconventional air-core reactor.In summary, the air-core reactor wound by large-inductance wire solves theproblems of the conventional air-core reactor, such as small inductance, large volume,serious electromagnetic radiation pollution, large power loss, big vibration noise andso on. Therefore, the research of air-core reactor wound by large-inductance wire hasan important practical engineering significance.