The Design Of The Dynamic Magnetic Motor Control System For Compressors

In current global energy conservation environment,compared with the rotary compressor,linear compressors have advantages in energy saving and high efficiency.The structure of linear compressor plays a vital role in the performance of compressor,it improves the efficiency of linear compressor efficiency through optimizing the structure of the linear motor.Based on the relevant information from domestic and abroad,an efficient linear compressor is designed,and the compressor is driven by the moving magnets.The moving magnet linear motor is composed of an internal stator,external stator and permanent magnets.The external stator is wind with the excitation coil,and the permanent magnet which are radically magnetized as mover conduct linear reciprocating motion.The mathematical model of electromagnet system,control system and dynamical system for the linear compressor are established based on the theoretical analysis.The gas force is linearized by describing function method,which provides a theoretical foundation for linear compressor structure design.The structure parameter optimization is carried out through Ansoft Maxwell,and the simulation mainly includes five aspects: gas gap distance,thickness of permanent magnets,length of permanent magnets,position of permanent magnets,and thickness of internal stators.In term of compressor controls,this kind of compressor has for advantages of variable piston stroke and operating frequency.By keep the compressor running frequency close to the resonance frequency based,the equilibrium position of the piston is stabled by adjusting the RMS(Root Mean Square)of input voltage.About the prototype test,the microcontroller STM32F407 is selected as the central processor,and the program of the moving magnetic linear compressor is designed in the Keil u Vsion5 programming environment.By adjusting the amplitude and frequency of the input sinusoidal voltage,the operating characteristics of no-load and load situation are analyzed,and the load capacitors are compared for the output characteristics of the drive circuit.Under no-load condition,the influence of input voltage on piston position is analyzed.Under load condition,the influence of gas force on the piston position,influence of the piston position on the electromagnetic force,influence of the piston stroke on the electromagnetic force areanalyzed in detail.Finally,according to the characteristics of the movement of the linear compressor,a method of automatically adjusting piston position is designed to improve overall operation efficiency.The experiment indicates: piston motion frequency is same to that of the input voltage.Under load situation,the closer the piston moves to the bottom of the cylinder,the greater the exhaust force will be,however when the distance between piston and cylinder bottom is too short,it would affect the smooth operation of the system.Under 55 Hz,100V sinusodial voltage input,series capacitor can increase 3.2mm piston stroke,exhaust force would increases to 2kg/cm~2.In load operation,under 10 Hz 100V sinusodial voltage input,after automatic adjustment of the piston position,the piston stroke increases 2mm,and the exhaust force increases 1kg/cm~2.It shows that this control method can eliminate the clearance and improve system performance effectively.