Instantaneous Electromagnetic Torque Components in Synchronous Motors Fed by Load-Commutated Inverters

Gabriel Ekemb,Fouad Slaoui-Hasnaoui,P M Lingom,Issouf Fofana,Joseph Song-Manguelle

doi:10.3390/en14113223

Abstract

This paper proposes time-domain analytical expressions of the instantaneous pulsating torque components in a synchronous machine air gap when supplied by a load-commutated-inverter (LCI) system. The LCI technology is one of the most used variable frequency drives when very high power and low speed are required in applications such as pipeline recompression and decompression, as well as liquefied natural gas compression. In such applications, synchronous motors are used because of their high efficiency resulting from a separated supply of the current to their rotor through the excitation circuit. These applications usually have long and flexible shafts, which are very sensitive to torsional vibration excitation when their natural frequencies interact with any external torque applied to the shaft. A torsional analysis is required by international standards to assess the survivability of the shaft through the overall speed range of the motor. Therefore, the magnitude and frequencies of the motor air-gap torque are needed for such evaluation. The proposed developments are supported by numerical simulations of LCI systems in a large range of operation range. From the simulation results, torque harmonic families are derived and expressed in a parametric form, which confirm the accuracy of the proposed relationships.

Highlights

IntroductionCrude oil produced by a set of wells is usually a mixture of gas, oil and water compositions
This paper proposed analytical expressions of the instantaneous electromagnetic torque in the air gap of a synchronous motor supplied by load-commutated inverters (LCIs) systems
These relationships are written based on voltage and current harmonic components in the stationary orthogonal reference frame

Summary

Introduction

Crude oil produced by a set of wells is usually a mixture of gas, oil and water compositions. These components are separated such that water is cleaned, disposed or reinjected into wells to improve wells pressure. Energy can be manipulated by changing the work or the heat of the molecules, which impacts their volumes. This is done by manipulating temperature with exchangers and coolers and by manipulating the system pressure with pumps and compressors [1]. The mechanical energy produced pumps and compressors is generally converted from electrical energy by using electric motors [2]. Hybrid drivers combining electric and gas-turbine drivers are used for large compressors, where a high-power electric motor (which power possibly exceeding 45 MW) is combined to a large gas turbine [3]

Objectives

Methods

Results

Conclusion