Linear induction motor drive characteristic analysis equivalent circuit and analysis method

Abstract

The invention discloses a linear induction motor drive characteristic analysis equivalent circuit and an analysis method. A Maxwell equation is combined with a winding function method, and a primary winding function, a secondary fundamental wave winding function and a secondary end effect wave winding function of a linear induction motor are obtained in terms of distribution of an actual primary winding of the linear induction motor. According to a winding function basic theory, equivalent inductance and the motion potential coefficient of the linear induction motor are analyzed and calculated, a voltage and flux linkage equation of the linear induction motor is built, and further, a novel equivalent circuit model of the linear induction motor is built. By means of the novel equivalent circuit mode, steady-mode and dynamic characteristics of the linear induction motor are analyzed. On the basis of the distribution situation of actual windings of the motor, influences of a transverse edge effect, a longitudinal edge effect and a primary semi-filled groove of the linear inductance motor on motor inductance and secondary resistance are reasonably considered, and drive characteristics of the linear induction motor are accurately and effectively analyzed.

Description

technical field [0001] The invention belongs to the field of linear induction motors, and more specifically relates to an equivalent circuit and analysis method for analyzing the driving characteristics of a linear induction motor. Background technique [0002] As the core component of the linear traction system drive, the linear induction motor (Linear Induction Machine, LIM for short) plays a pivotal role. However, since the two ends of the primary longitudinal magnetic circuit of the linear induction motor are disconnected and the primary and secondary air gaps are large, it has the following characteristics: (1) Even if an asymmetrical three-phase current is generated under the action of a symmetrical external voltage, they will be in the air gap The positive-sequence forward magnetic field, reverse-sequence reverse magnetic field and zero-sequence pulsating magnetic field are generated in it. Among them, the reverse-sequence and zero-sequence magnetic fields will genera...

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Problems solved by technology

However, since the two ends of the primary longitudinal magnetic circuit of the linear induction motor are disconnected and the primary and secondary air gaps are large, it has the following characteristics: (1) Even if an asymmetrical three-phase current is generated under the action of a symmetrical external voltage, they will be in the air gap The positive-sequence forward magnetic field, reverse-sequence reverse magnetic field and zero-sequence pulsating magnetic field are generated in it. Among them, the reverse-sequence and zero-sequence magnetic fields will generate resistance and increase additional loss when the motor is stationary or running, thus affecting the force-energy characteristics of the linear induction motor and work efficiency

(2) The distribution of transverse magnetic flux density is uneven, the equivalent resistivity of the secondary conductor plate increases, the effective magnetic field of the air gap is weakened at the input end, and the output end is strengthened, making the traction force pulsate, the difficulty of motor control increases, and the traction coefficient decreases, seriously It will exacerbate the unbalance of three-phase current and generate greater resistance

(3) After the magnetic circuit is broken, the number of windings at the end is half of the middle, and the longitudinal magnetic flux density and current density have changed, which affects the equivalent parameters and traction characteristics of the motor

Electromagnetic field calculation methods include analytical method and finite element method, which require a large grid division area or special dynamic grid division technology. The electromagnetic field calculation takes a long time and data processing is very cumbersome. Under different working conditions , the setting of boundary conditions and grid division are very particular, if the setting is unreasonable, it is difficult to get a reasonable understanding

The equivalent circuit method mainly includes the series and parallel circuit model method, which has a clear concept and is simple and easy to implement, but there are many assumptions in the calculation and the accuracy is poor

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