Study On The Harmonic Character Of The Magnetic Controllable Reactor In The Soft-starting Of Asynchronous Motor

Direct start of larger and medium-sized power rating motor will generate highstarting current surge which could possibility cause voltuge drop, protection devicestripping and other abnormalities. Now, soft start is widely used to solve theseproblems caused by direct start.The soft starting device based on magneticcontrollable reactor (MCR) has become of a important soft starter of high voltage andlarge current AC motor.Simulation work and experimental analysis of magnetic soft start is studied inthis paper. Harmonic characteristic of the soft-start magnetron reactor is studied inaddtion. The main contents are as follows:(1) Detailed description of basic principles and operating characteristics of themagnetron reactor. Electromagnetic equations and the simplified equivalent circuit ofthe magnetic control reactor is deduced and the working characteristic of magneticcontrol reactor were analyzed. Build the equivalent circuit of the magnetic controlreactor and analyse this simulation model in the simulation software MATLAB.(2) Put forward a new type of MCR work with independent excitation.MCRwork with self-excitation presently widely used for magnetic controlled soft starter onthe market, this scheme has a certain advantage of no requirement of the externalexcitation source. On this basis, this paper puts forward the MCR with independentexcitation. Compared with the former, while the new scheme need the excitationsource, but the power capacity only for about2%of the reactor volume, with overallcost advantage.(3) Analysis of the harmonic characteristic of the three-phase MCR, it showsthat the star connected three-phase MCR’s harmonic characteristic can be improved ifthere is a delta-connected zero-order winding on the magnetic circuit of three-phaseMCR, which is used for harmonic suppression.(4) Analysis of the basic principle of asynchronous motor reduced voltagestarting and the structure of the magnetic controlled soft starting system. Build a simulation model of magnetic soft start system to realize the simulation of currentlimit soft-start. Then we conduct an experiment based on existing soft starter, theresult shows that the new scheme has a good performance on current-limiting starting.(5) Analysis of the harmonic characteristic of the current in the magneticcontrolled soft starting. It shows that preliminary excitation can improve thewaveform of the starting current in the initial stage, and the harmonic generated by themagnetic controlled soft starter is small.This paper research the magnetic controlled soft starter with independentexcitation based on simulation analysis and experimental validation. The analysis ofthe harmonic characteristic of the current in the magnetic controlled soft starting ishelpful to guide the design of magnetic control soft starting system..