Research On Application Of Pre-excitation Start Of Mine Hoisting Machine

The motor the mine hoist used is belong to high power AC Induction motor, and itis necessary to involve the AC speed regulation during the operation of mine hoist. TheAC speed regulation is becoming more and more popular because of its excellentcontrol performance and wide adaptability. Now,the main method of the AC speedregulation is Vector control. Although the Vector control has its advantage during theoperation of motor, it also does not have good performance at the moment of thestarting. The peak current will achieve three to five than the steady current when themotors used the general Vector control to start. This phenomenon can cause device’sfailure,and have bad effections on the whole mine hoist system.In the light of the peak current is too large for this phenomenon when the motorstarts, this thesis presents a new type of pre-excitation compound control scheme basedon traditional vector control: establish magnetic field before the motor starts, thecontroller makes sure that flux linkage is established in some phase of stator, then turnto traditional vector control when the motor starts. The flux component and torquecomponent are decoupled dynamically during this process. After the motor takes thisnew method,the results show that the start current vary smoothly which avoidsignificant pulse contrast to other start-up method. Meanwhile output torque responseis rapid. It has important meanings to improve the safety of the motor’s starting.In this paper, the application of certain depth of induction motor vector controlpre-excitation and the start of pre-excitation start frequency control system in practicecarried out,the main content:1. Summarize and analyze the development and current situation of mine hoistAC frequency converter and motor starting. From the control strategy for inductionmotor VVVF start-up, to explain the necessity to reduce the peak current when the motor starts. Summary several kinds of induction motor control method to reducestarting current, and analyzes the characteristics and limits of each method.2. According to the basic theory of mathematical model of the induction motor,the basic equation of voltage and current in the rotor flux oriented vector control isanalyzed. Pick out the parameter equations which can affect the starting current toanalysis deeply.3. Research a new type of pre-excitation compound control scheme based ontraditional vector control. Through analysis the vector control DQ current equations ofvariable frequency speed regulation system model, find out the reasons for the motorstarting current is so large. Aiming at the shortcomings of traditional vector control atthe start moment, put forward corresponding AC pre-excitation and DC pre-excitationmethod in motor starts. Through these two methods can significantly reduce the peakcurrent when motor starts,and the motor can obviously improve the performance at thestart moment.4. Build the whole induction motor pre-excitation system, from the hardwarecircuit perspective-schematic diagram design and the selection of devices, and fromthe DSP software program compilation perspective. Comprehensive and systematicdescription of the simulation platform of pre-excitation start, and some simulation andexperimental results and illustrations are also presented.