THE METHODIC OF CALCULATING THE CURRENT DENSITY DISTRIBUTION IN THE DISK-SHAPED ROTOR OF ELECTRODYNAMIC BRAKE

• Дата: 2018
• Автор: Tsygankova, G.
• Формат: Стаття
• Мова: Українська
• Опубліковано: Institute of Renewable Energy National Academy of Sciences of Ukraine 2018
• Теми: electromagnetic field; current density; electrodynamics brake.
• Онлайн доступ: https://ve.org.ua/index.php/journal/article/view/181
• Назва журналу: Vidnovluvana energetika

The article deals with the disk electrodynamic brake, which can be used to control the rotation of the rotor of wind power plants of low power. Due to its simple construction and small dimensions, the brakes are conveniently integrated into the working bodies of the wind turbines. It is accepted that a stationary inhomogeneous magnetic field is excited by a direct current of a ring winding of an inductor with a rack-and slot working surface. The methodic of calculating the current density in the disk-shaped rotor of electrody namics brake with a working air-gap in the rack-and-slot configuration of the magnetic stator, taking into account the thickness of the disk is worked out. To solve the system of equations in the rotor and the air gap, a model for replacing an inductor with a double-toothed gap by a uniform interval formed by flat smooth surfaces of the inductor is adopted, on which the imaginary surface currents are located, that causes the inhomogeneity of the magnetic field. The superficial density of imaginary currents is chosen depending on the harmonic composition of the magnetic field strength in the working gap at a motionless rotor.The system of equations of the electromagnetic field in the electroconductive environment reduced to equations for component of harmonic component of current density, recorded in a cylindrical coordinate system. The system is reduced to the equation in partial derivatives of the second order relative to the radial component of the current density. The solution of this equation is obtained - the formula for calculating the current density in a disk rotor, depending on its size, according to a given initial value of the harmonic component of the magnetic induction in the working gap at a motionless rotor. The given ratios for calculation of losses on the density of currents allow determining the electromagnetic moment. Since the frequency of rotation is explicit included in the expression for the electromagnetic moment, it is possible to estimate the behavior of a wind turbine unit equipped with such a braking device, with a sudden change in wind speed. The found analytical relations concerning characteristics of an electromagnetic field give an opportunity to conduct their analysis and solve the problem of calculating the size and design of such disc-shaped devices for practical application in wind power plants.