PERFORMANCE AND ANALYSIS OF CHOPPER FED D.C. SERIES MOTOR UNDER REGENERATIVE BRAKING

ABSTRACT

The paper presents a method of analysis and performance of chopper fed dc series motor under regenerative braking. The method of analysis takes into account the nonlinearity of the magnetic circuit, armature reaction, effect of commutation pulse and source inductance. Equations have been derived for the calculation of (a) machine speed-torque characteristics (b) regenerative power and efficiency of regeneration, and (c) current ripple and filter inductance value. The method also shows the prediction of stability at low speeds and conditions for failure of regeneration. The effects of chopper operating frequency, source inductance, commutation capacitor and input-filter capacitor on regenerative power and efficiency of regeneration, and stability of braking have been described. Theoretical deductions have been verified experimentally     

GENERALIZED METHOD OF ANALYSIS OF CHOPPER-FED DC SEPARATELY EXCITED MOTOR UNDER REGENERATIVE BRAKING

ABSTRACT

A generalised method of analysis for predicting performance of d.c. separately excited motor under regenerative braking controlled by load current commutated chopper, has been presented. It has been shown that the source inductance, in the absence of filter capacitor at the source terminals, considerably influences the chopper commutation and machine performance. It has experimentally been shown that the use of a suitable filter capacitance at the source terminal neutralizes the effect of source inductance. Calculated characteristics agree well with the experimental results     

DYNAMIC MODEL OF CHOPPER FED DC SEPARATELY EXCITED MOTOR

ABSTRACT

This paper describes the transient response of a chopper fed dc separately excited motor using time ratio control. An approximate second order model for predicting the transient behaviour of the motor is developed using perturbation technique. The transient response for small and sudden variations of duty interval and load torque is deduced during discontinuous and continuous current mode operations. The effect of external inductance on the performance of motor in the armature circuit has also been investigated. The results are compared with those obtained from a digital computer by numerically solving the simultaneous differential equations valid for different intervals of chopper cycle and also with the first order model. It is shown that the second order model is more accurate than the first order model and much simpler and efficient than the numerical approach. The theoretical results obtained are also verified with an experimental set up. Experimental results closely agree with theoretical predictions.     

ANALYSIS OF STATE FEEDBACK CONTROL OF CHOPPER DRIVEN SEPARATELY EXCITED D.C. MOTOR

ABSTRACT

Armature voltage control of d.c. motor speed to a set point in the face of large step torque changes can be treated as a regulation problem in linear system theory. By proper pole assignment, one can have complete control over the dynamics of the closed loop system. The control input comes out as a function of the states, motor speed and armature current respectively, and integral of the output (speed error). The paper deals with separately exicited d.c. motors fed from a thyrister chopper circuit controlled by the state feed back signal. Discontinuous mode of current conduction in the chopper gives rise to unwanted swings in the dynamic response of the system. The proposed approach models the system taking discontinuous mode of current conduction into account, obtains the feed-back constants and predicts the oscillations that may come into picture at low shaft torques. Also a time varying model in proposed and this gives the designer an insight into the working of the system and guides him in his choice of the feedback coefficients. The proposed regulation method has been tested on a laboratory model d.c. motor, and the experimental and the theoritically predicted response curves are found to be in agreement     

SIMULATION OF CHOPPER FED D. C. MOTOR DRIVE SYSTEM-PROBLEM ORIENTED APPROACH

ABSTRACT

The purpose of this article is to develop an efficient simulation program for the steady state performance of a chopper fed separately excited D.C. motor drive system. The effectiveness of this method lies in the evaluation of the initial state vector of a state equation representing chopper-electromechanical system without passing through the transient region. Effects of source impedance, chopper circuit configuration/parameters have been discussed in detail to prove the generality of this simulation approach.     

TRANSIENT ANALYSIS OF CONVERTER-CONTROLLED DC SEPARATELY EXCITED MOTOR

ABSTRACT

Three methods of transient analysis of a de separately excited motor controlled by a phase-controlled converter have been derived. These methods are compared with regard to accuracy, computation time and usefulness.     

A NEW APPROACH TO PERFORMANCE ANALYSIS OF CHOPPER CONTROLLED D.C. MOTOR DRIVE

ABSTRACT

An analytical method for performance analysis of a d.c. separately excited motor fed from a chopper is presented. The motor input voltage is represented as a series of step-voltages with a time phase difference. The system equations are solved to obtain closed-form solutions for motor current and speed, for transient as well as steady state conditions. The method presented is superior to existing methods in that the solution is in closed-form, and does not make recourse to recursive numerical techniques. The solutions for steady state condition corresponding to any set of operating conditions (voltage, chopper duty factor, load torque) can be directly obtained. The computational effort and time needed is therefore extremely small as compared to other methods.     

TRANSIENT ANALYSIS OF BRAKING MODE OPERATION OF INDUCTION MOTOR FED FROM A VARIABLE FREQUENCY SOURCE

ABSTRACT

The transient behaviour of a three phase induction motor in the braking mode is investigated when the motor is fed from a variable frequency source. Appropriate voltage and frequency conditions to ensure minimum stopping time for plugging as well as for the case when plugging is used in conjunction with regenerative braking are identified. A dynamic model has been developed using the theory of instantaneous symmetrical component and associated operational equivalent circut and therefrom the transient performance of the motor in both the cases are compared with that of the normal plugging.     

3kW开关磁阻电机的再生制动实现

该文分析了开关磁阻电机再生制动的原理和控制方法,给出了一套3kW开关磁阻电机再生制动的设计实例,在电流控制的基础上解决了位置检测、优化控制以及系统保护等再生制动过程中不容忽视的问题.理论和实践表明,在电流控制的基础上,中小功率开关磁阻电机具有优良的再生制动性能,这对降低系统成本、提高系统性能/价格比和开拓开关磁阻电机的多种应用具有重要意义.     

PARAMETER IDENTIFICATION OF A SEPARATELY EXCITED OC MOTOR FOR SPEED CONTROL

ABSTRACT

This paper presents the application of the least error squares (LES) parameter identification algorithm to. obtain parameters of a separately excited DC motor. The parameters of interest are; the resistance and inductance of the armature windings (Ra.Lt). the motor inertia (J), the damping constant (D), the torque and back emf constant (K) and the load torque constant (μ.). The data used are the motor input voltage, and the corresponding rotor speed. It is assumed that the trajectory of the motor speed as well as the corresponding input voltage are known and sampled at a preselected rate. Simulation results for a separately excited dc motor used in robotics are reported showing good agreement with actual parameter values.     

PERFORMANCE ANALYSIS OF LOAD COMMUTATED INVERTER FED CAGE INDUCTION MOTOR DRIVE

ABSTRACT

An approach, to analyse the performance of a variable speed cage induction motor drive fed from load commutated inverter (LCI), is presented. Induction motor with an appropriate capacitor across its stator terminals constitutes the load on the inverter. A fully controlled bridge converter, supplied by a variable dc voltage source, commutated with the back emf of the motor, acts as an inverter. An algorithm to compute the motor performance, is developed using equivalent circuit representation of the system. Strategies for the selection of control variables, in order to achieve the desired speed range for satisfactory performance of the drive are given. The performance of a 3-hp, cage induction motor fed from LCI is computed, using the developed algorithm for wide range of speed; and is verfied experimentally.     

具有弱磁调速的他励直流电机非线性多输入多输出控制器的设计

针对具有弱磁调速的他励直流电动机模型，该文将常规励磁电流调节器、电枢回路速度调节器、电流调节器合而为一，将励磁电流同电机的速度、电枢电流一样取为状态变量，按照多输入多输出(MIMO)非线性系统，尝试性地设计了一种MIMO励磁及速度控制器。该控制器结合负载转矩自适应估计技术，并利用状态反馈线性化技术和极点配置方法进行设计。仿真结果表明，针对冷连轧机某机架驱动用他励直流电机所设计的非线性MIMO励磁及速度控制器，对负载转矩摄动有较强的自适应性和鲁棒性。电机从低速启动到基速及最高速度运行时，动静态性能优良，从而验证了该文所提出方法的有效性。     

ANALYSIS AND CONTROL OF TORQUE PULSATIONS IN CURRENT FED INDUCTION MOTOR DRIVES

ABSTRACT

Three types of feedback compensation schemes are described which can be used to reduce the torque pulsations which normally occur when induction machines are supplied from a current source inverter. The approach is verified both by a detailed computer simulation and also by test results from an actual system. Limitations of the method near zero slip frequency (no load) is discussed and a means suggested for elimination of the problem.     

APPROXIMATE ANALYSIS OF TEMPERATURE RISE IN AN INDUCTION MOTOR DURING DYNAMIC BRAKING

ABSTRACT

The problem of two-dimensional transient heat flow in the stator of induction motor is solved by use of a finite element formulation and arch-shaped elements in the r-θ plane of the cylindrical co-ordinate system. The shape functions and exact solution matrices are derived algebraically for utmost economy in computation. The temperature distribution has been determined considering convection from the stator frame and cylindrical airgap surface. Finally the temperatures obtained by this two dimensional approximation have been compared for different stator currents considering the time required for each stator current during the transient.     

实心转子永磁同步电动机的动态转子参数及起动特性的计算

采用场路结合的方法,建立了求解了二维涡流场方程－－定子电压方程的耦合有限元方程。并借助了电路分析,计算实心转子永磁同步电动机起动过程 的动态转子参数,同时用端部系数计入端部效应的影响,从而获得转子胡滑差ｓ的变化曲线。在此了建立永磁同步电动机卢动过程的计算机仿真数学模型,用龙格－库解之,便可得到各种动态特性。此法可用于研究电机的起动特性、分析电机参数和永久磁钢特性及电机劝性能的影响,进而可改进电机的     

基于瞬态模型的不对称供电三相感应电动机分析

三相电压不对称对感应电动机性能影响较大，本文建立了三相感应电动机瞬态模型，基于该模型和复数不平衡因数（CVUF)的概念，研究不对称供电电压对感应电动机性能的影响，对不对称三相电压供电感应电动机起动过程进行了仿真，计算了不同CVUF时感应电动机的起动过程，研究了起动过程中的峰值转矩，起动时间、达到稳态后的三相电流不平衡因数，转速，转速波动，转矩波动与CVUF的关系，得出了相应结论。     

永磁磁滞同步电机运行特性分析

对一种新型的永磁磁滞同步电机进行了实验测试和理论分析。考虑磁滞内涡效应和磁滞效应,对电机地全面的仿真。实验的测试数据与仿真结果相吻合,这说明仿真模型及作为其理论基础的数学模型的结构是正确的。结合实验和仿真的结果,就永磁体对电磁转矩、电流特性、转速特性的影响进行了深入分析．实验测试的数据以及仿真的结果表明,在稳态电流与同步牵入转矩方面的产滞电机相比永磁磁滞同步电机的性能有明显的改善,它是一种很有实用     

PERFORMANCE ANALYSIS OF A D.C. DRIVE ELECTROMECHANICAL SYSTEM WITH ELASTIC COUPLING AND PULSATING LOAD TORQUE

ABSTRACT

This paper presents the analysis of a d.c. motor drive with a pulsating load torque and elastic mechanical link between the motor and the load. A mathematical model of the system using State Space technique is given and the equations are solved to obtain closed-form solutions for motor speed and current under transient and steady state conditions. The analysis reveals that the system performance is significantly affected by elasticity of the shaft and the nature of pulsation of load torque     

PERFORMANCE ANALYSIS OF THE REPULSION MOTOR CONTROLLED VIA ROTOR TRIAC

ABSTRACT

This paper investigates the solid state speed control of a repulsion motor using a triac in the rotor circuit. The speed control is accomplished by varying the triac firing angle. In addition, this paper investigates the harmonic contents of the rotor current, stator current and rotor voltage The waveforms of these variables were generated and then analyzed numerically for their harmonic content using a Fouries Series Subroutine. The results were validated by comparison with obtained experimental results. More over, the harmonics generated using this type of speed control are compared with those generated when the motor is controlled via a triac in the stator cicuit.     

PERFORMANCE ANALYSIS OF A HIGH STARTING TORQUE SINGLE-PHASE INDUCTION MOTOR

ABSTRACT

The objective of the work described is to make an assessment of the possible use of three-phase induction motor working as a single-phase motor. The analysis is performed on the proposed winding arrangement, introduced previously by same authors. The analysis includes all motor windings, whereas the conventional analysis is performed on the running winding only. The motor windings are analyzed through the stationary direct and quadrature axes. The magnetic field and E.M.F's of the motor are studied at starting, run-up and running operation. Hence, d-q axis equivalent circuits are deduced to represent the motor at different modes of operation, taking into consideration the core losses and sturation effects. Prediction of the run-up and running characteristics of the motor under investigation is achieved by solving the equations of equivalnet circuits in a simple manner. The predicted results are compared with the releavant experimental results. Good agreement has been achieved, and this confirms the validity of proposed analysis.