Energy Consumption Characteristics Of Variable Speed Motor Systems Under Different Load Types

A reliable and reasonably accurate loss model of variable speed motor systems is important for its performance prediction and energy consumption analysis.Most of the existing methods are based on the finite element analysis,but the disadvantage lies in the computational difficulty,which is not suitable for practical application.This thesis establishes a practical simulation model of variable speed motor systems based on MATLAB/Simulink.The converter losses are calculated by analytical model of IGBT and Diode,and the iron losses in variable-frequency motor is considered as variable iron loss equivalent resistance.The efficiency of the motor system under different conditions is analyzed,and it shows that traditional models of motor systems may cause errors when determining the optimal system operating point,with the converter losses neglected.The main work is as follows:1.Through the principle of the PWM inverter and load test results of the analysis shows that the drive loss and load rate and power supply frequency;study of the frequency power supply on the loss of induction motors,the power of harmonic components revealed The effect of skin effect on rotor copper loss is discussed.A frequency-variable motor model based on S-function is established.A practical model based on MATLAB / Simulink is proposed and validated by experiments.2.The simulation of inverter motor system with constant torque load and fan and pump load is carried out.The influence of carrier frequency on energy consumption of frequency converter is analyzed in detail.The variation of loss of inverter and motor under different frequency and load rate And the overall energy consumption level,and gives the best energy-saving operating point.The results show that there is a certain deviation between the optimal operating point of the motor system and the motor itself,which means that the whole system can not reach the most energy-saving running state when considering energy-saving control of inverter motor.3.The experimental validation is also performed on a 5.5kW motor.The achievement of this thesis can provide technique support for the optimal control strategy for motor systems.At the same time,taking into account the inverter output waveform contains a large number of high-frequency components,the actual measurement of the instrument sampling accuracy of the PWM voltage waveform.