Research On The Theory And Design Of Variable Polar Distance For The Double-sided Linear Induction Motor

The electromagnetic ejection system consists of four subsystems, energy storage system,power electronic system, linear motor drive system and control system. Linear motor is the power source of the driving system, which is used to drive the load directly. It is applicable to electromagnetic catapult mainly including linear induction motor, permanent magnet linear synchronous motor and superconducting excitation linear synchronous motor. Since linear induction motor is of secondary structure which claims as strong, small mass, low manufacture cost and running cost, as well as safe and reliable operation and high power inverter switch device with low switching frequency, therefore, long primary double-sided linear induction motor is selected to be the driving motor of the acceleration.A new drive method has been proposed for acceleration drive, a double-sided linear induction motor with constant frequency and varying pole pitch by analyzing the core drive system and the particularity of electromagnetic acceleration. The traditional linear motor control usually adopts control frequency of current to control the electromagnetic thrust output, and requires a real-time detection speed displacement feedback. When operating at high speed, the current frequency it requires increases thus getting subject to the limitation of the switching frequency of the inverter. Therefore, the current frequency of the proposed variable distance of linear induction motor is invariable in the acceleration, and there is no need to feedback control. In this way it can optimize control mode as well as reduce the motor loss.In this thesis, establish one-dimensional and two-dimensional field equation of the variable distance bilateral linear induction motor and analysis of air gap magnetic field components, solve the air gap magnetic induction intensity expression, and analyze the influence of end effect on air gap magnetic field, and change in the spacing of the intensity of magnetic field and end effect influence. It also analyzes the influence on the dynamic performance of the motor according to the magnetic induction intensity expression of the air gap magnetic field.Secondly, the equivalent circuit of long primary double linear induction motor is deduced.The end effect co-effects on end effect correction, and calculates the correction coefficient of expression. It also manages to analyze the spacing of the changes of equivalent circuit parameter values, and also conduct the theoretical simulation analysis of the impact of changes in the distance of end effect characteristic parameters.Again, according to the actual requirements, the distance of linear induction motor design parameters changes calculation and selection, simulation analysis of the spacing of the changes of magnetic circuit and circuit parameters. Meanwhile putting forward two design methods of the distance transform and piecewise continuous transformation of two kinds of variable distance linear motor.Subsequently, the variable pole model developed into disguised width and inferred size expression based on an arbitrary position facies width and at any position of anode.Meanwhile analyzes the effect of secondary parameter, air drag and other external factors on the performance of the motor. Other than that, it also analyzes the change of air gap magnetic field of the polar distance continuous and calculate the magnetic induction intensity of different regions of the variable distance long primary double-sided linear induction motor. It derives the variable pole motor, the winding self-inductance and mutual inductance formulas,and also derives the electromagnetic force and maximum electromagnetic thrust value, and makes a simulation analysis of the spacing of the changes on the performance of the motor.On top of these, it makes the simulation analysis of the distribution of magnetic flux and magnetic flux density; verify the validity of the theoretical calculation by using the finite element simulation software.Finally, with a linear induction motor equivalent circuit as the basis, q-d-0 coordinate system as a benchmark, it proposes a new drive control strategy and constant current frequency, optimal acceleration control thus establish variable distance linear induction motor dynamic model and conduct an imitation analysis of motor in frequency control of the dynamic characteristics.