Application Catalog

195 - Torque characteristics analysis of three-phase induction motors using 3D correction function

2014-12

Module: DP, TR

Overview

An induction motor is a motor in which the rotating magnetic field of the stator winding causes induced current to flow in an secondary conductor, which exerts force on the rotor in the rotational direction and causes it to spin.
In an induction motor, magnetic flux in the axis direction, such as leakage flux in the coil end, can have a large effect on motor characteristics. However, transient phenomena are strong in the inductance motor, and analysis time is needed in order to achieve a steady state solution. Due to this, being able to evaluate characteristics in a 2D analysis is desirable, but 3D effects such as leakage flux in the coil ends are ignored in a 2D analysis, and there are cases when an accurate analysis cannot be obtained. In JMAG, highly accurate results can be quickly obtained by performing corrections on 3D effects.
This document introduces introduces a case study which obtains inductance correction values, and then obtains N-T characteristics (revolution speed-torque characteristics) using the 3D correction function.

Leakage Inductance

Fig. 1 compares torques between one that does not account for eddy current inside the magnetic steel sheet during magnetic field analysis, and one that does. It shows that transient phenomena occur in the early stages of analysis when accounting for eddy current. Table. 1 shows the average value of an electric angle between180 to 360deg. When the revolution speed is high like in this motor, the torque is overestimated when eddy current is not accounted for in the magnetic steel sheet.

N-T Characteristics

Fig.2 shows those N-T characteristics of 2D, 3D and 2D analysis with 3D correction and fig.3 shows N-I characteristics.
Fig. 2 shows that N-T characteristics becomes the same as 3D by using 3D correction. As shown in fig.3, this is because current flowing in the coil has come closer by accounting for leakage inductance.