Daily Archives: 16 March 2015

Design of Separately Windings Control System of Series/Compound DC Traction Motors

16 March 2015Fără categoriecburada

Abstract 

This paper focuses on the problem of the control system of Series/Compound DC motor in both areas of speed adjustment. Traditional field weakening is achieved by means of resistances  and contactors wich  inserting  and/or shunting in  field circuits. It is characterized by shock currents, torque and speed as well as by increased energy consumption. To eliminate these disavantages  paper proposes separate control of  armature,  series and shunt windings  of Series/Compound DC motor and supply their own power converters. Keeping hyperbolic mechanical characteristic of these motors requires setting the series field  current equal to or less than armature current. Developed control system is equipped with a single loop for series field and two loops for armature with a  current and speed controllers. Imposing series excitation current required is achieved through a special computer based on actual values ​​of current and rotor speed. Control system design was made based on a mathematical model and   use  of default instrument of Matlab-Simulink for tuning of PID controllers. Simulation results demonstrate the system’s ability to control separate windings for continuous speed adjustment in both areas, strictly limiting the rotor current, reducing energy consumption and ensuring the imposed  performance indicators. The proposed control method is recommended for use in electric

Transmission and Processing of the Measurement Signals Generated by a Transformer for the Current Measurement in Medium Voltage Networks

16 March 2015Fără categoriecburada

Abstract 

The trends to improve the performances of the classic instrument transformers was oriented to introducing new materials, components and methods in its design, manufacturing and operation. This paper presents the technical solutions adopted to implement the measuring system at medium voltage based on this current instrument transformer. The transformer uses a fiber optic link to send the measuring signal from the medium voltage point to the monitoring point. The structural block diagram of this transformer is presented and the operation of the main blocks is described. On the monitoring side, the measuring signal is converted from the voltage signal at the current signal which flows through a current loop for remote control and telemetry. Also, analog to digital conversion and the sending of the result of measurement at master monitoring system is possible. A simple algorithm for remote control of the operation of  transformer is presented. If the transformer is integrated into a digital measurement system then it operates as a slave unit under the control of the master unit. The samples taken from the measurement signal are used for digital processing. It is analysed the possibility to realize a network of transformers using the communication bus RS 485 . Finally, the waveforms, recorded during the performed tests, are presented.

Design and Analysis of Low-Cost Ferrite Permanent Magnet Assisted Synchronous Reluctance Rotor and Permanent Magnet Synchronous Rotor with Flux Concentrator

16 March 2015Fără categoriecburada

Abstract 

Rare-earth magnets which are the best solutions for PMSM rotors are expensive which makes that other types of motors are used in the applications. The solution of the replacement of these motors with PMSynRM that use low-cost type of ferrite magnets becomes more tempting lately. This paper proposes two different types of low-cost ferrite solutions: first a V permanent magnet assisted synchronous reluctance rotor (VPMSynRM) and the second a permanent magnet synchronous rotor with flux concentrator (PMSM-FC) as an alternative solution to the rare earth inserted tangential permanent magnet synchronous motor (PMSM). For the first situation, this paper proposes two topologies of PMSynRM: with one row and respective two rows of flow barriers, equipped with ferrite magnets Finite element (FEM) approach has been utilized to show the performance of the proposed rotors. The purpose of the proposed solution is to replace only the rotor of such a PMSM that is already in production, so the size of the stator and the number of windings will remain unchanged. Finally, for the PMSM-FC, the experimental results have been shown. This one is considered competitive, taking into account the resources required for a limited-series manufacturing. The motivation of this study is to reduce the cost of the rotor by changing the type of PM and by the choice of suitable rotor geometry.