Induction Motor Computer Models in Three-Phase Stator Reference Frames: A Technical Handbook

When mathematical models of electromagnetic devices are described by ordinary differential equations, then the magnetization curves of their cores are often expressed with a help of nonlinear coefficients. Sometimes such an approach is considered questionable, and therefore, the purpose of this chapter is to prove its admissibility. 

This chapter is dedicated to an algorithm of approximate calculations of three-phase induction motor equivalent T-shaped circuit parameters such as resistances and inductances. These calculations are conducted with the use of catalog or reference book data containing information related to rated shaft power, angular speed or slip, efficiency, power factor, line RMS voltage and the ratio of starting to rated currents.

 In this chapter, authors suggest an approach to the shaft load simulations and calculations of the electrical machine efficiency with the use of OrCAD PSpice Designer Software, and in particular, visual programming of analogue component blocks. Also, a method for modifying the EM dynamic model is put forward. This method enables researchers and designers to acquire data for plotting static mechanical, electromechanical and performance curves vs the angular speed of the rotor. These data are obtained by modifications to the block-diagram of the motion equation of the drive where the instantaneous values of the electromagnetic torque of the motor and the load torque are equal by absolute values and opposite to each direction.

A new approach to the shaft load simulation with the different types of fluid coupling is introduced herein. The presented simulation results are obtained for an electrohydrodynamic drive at different load modes and types of fluid coupling such as: with constant filling; static self-emptying (traction fluid coupling) and dynamic self-emptying (limiting fluid coupling). The chapter also provides an example of fluid coupling parameters and characteristics as well as depicts the following operation modes of the system: acceleration; no-load; load and overload on the turbine shaft. 

The author proposes an improved version of the mathematical and computer model of a three-phase induction motor in the three-phase braked coordinates (in the three-phase stator reference frame), which proves the correctness of the starter winding asymmetry considerations in electrical machines. The chapter presents the parameters and characteristics of an induction traction motor type STA-1200 manufactured in Ukraine. A comparative analysis of the simulation results for intact and damaged motors has been carried out.

This chapter provides an electrical schematic diagram of the power circuits of an auxiliary electric drive with a capacitive phase splitter and 3-phase induction motors onboard of an AC electric locomotive and the statistics and root causes of typical failures of the induction motors operating as part of such a circuit. A conclusion is made about the expediency of simulating thermal processes in the auxiliary induction motors.

This chapter discusses the start-up simulation results of auxiliary drives of fan and piston-type air-compressor driven by three-phase induction motors. The computer model described in this chapter simulates a relay-contactor type system of auxiliary machines powered from the secondary winding of the traction transformer through the capacitive phase-splitter. The authors make an analytical comparison of the start-up process at different values of the grid voltages. Comparative assessments of the simulation-based and experimental oscillograms of voltages, currents and the rotational speed of the motor-fan and motor compressor during the start-up process are described. 

This chapter is dedicated to the consideration of the possibility of building a thermal computer model of an induction electric machine with a squirrel-cage rotor. The thermal model is considered as an add-on to the computer model that describes electrical and mechanical phenomena of the IM. Both models are included in a single OrCAD project. The structure and components of the developed thermal model are described. The thermal processes modeling results in an induction motor type NVA-55 as part of an auxiliary electric drive of a freight electrical locomotive are presented taking into account the unbalanced supply voltages and squirrel-cage defects.