Asynchronous Performance Prediction of AC Permanent Magnet Motor

many permanent magnet synchronous motors are run up from standstill by a sudden connection with an ac supply. The cage windings in rotor slots produce induction motor torque to run up the rotor, but two torque dips are produced in the torque-slip curve of the permanent magnet motor; one is caused by the rotating permanent magnet, and the other by the magnetic and the electric asymmetry between the direct and quadrature axes. Therefore, the prediction of the asynchronous performance is very important, as motors cannot be run up, unless the minimum values of the torque dips exceed the load torques at the slips. In this paper, ``harmonic permeance coefficient' is newly introduced, which is used to combine the finite element field solution with the calculation of air gap inductance, and equations for the calculation of asynchronous performance of permanent magnet motors are also expressed. The calculated value by these equations agreed well with the experimental results.     

Design features and protection of valve actuator motors in nuclearpower plants

A status report on an effort of the Working Group IEEE-NPEC-SC4.7 is presented and the performance requirements, selection, design, and protection of valve actuator motors (VAMs) commonly used as components in direct gear driven valve actuator assemblies in nuclear power plants are discussed. VAMs are short-time-rated, high torque-to-inertial ratio motors. The actuator manufacturer selects the performance parameters for the VAM based on the maximum thrust required by the valve for tight shutoff. Since valve actuators require a high starting torque, the rating system begins with the assignment of nominal starting torque. The requirement of minimum frame size dictates a minimal (running) torque and a minimum run time. Design features of the VAM leading up to its design as a short-time-duty rated motor are described and compared with a continuous-duty motor designed to NEMA MG1. The unique features of the speed-torque characteristics and performance at varying voltages and temperatures are described     

Analysis of torque developed in axial flux, single-phase brushless DC motor with salient-pole stator

An analysis of the torque developed by a single-phase disc brushless permanent magnet motor with salient-pole stator is presented. The machine represents a new family of brushless disc motors with the starting torque issue appearing to be most challenging. To produce a starting torque, the permanent magnets on one of the rotor discs are distributed nonuniformly. However, this significantly distorts a shape of the cogging torque versus rotational angle characteristic which, in turn, affects a waveform of the overall torque. A three-dimensional (3-D) finite-element model is used for the purpose of determining of angular variations of the torque developed by the motor. To find how the torque varies with time, a model of the source-inverter-motor circuit is developed. A simulation study on an influence of the commutation angle on the electromagnetic torque is also a subject of this paper. The results obtained show that the motor performance can be improved by a proper selection of the current commutation angle to reach the maximum efficiency. The simulation results are in good agreement with measurements obtained from a prototype motor.     

Asynchronous performance analysis of a single-phase capacitor-start, capacitor-run permanent magnet motor

This work presents a detailed analysis of the asynchronous torque components (average cage, magnet braking torque and pulsating) for a single-phase capacitor-start, capacitor-run permanent magnet motor. The computed envelope of pulsating torque superimposed over the average electromagnetic torque leads to an accurate prediction of starting torque. The developed approach is realized by means of a combination of symmetrical components and d-q axes theory and it can be extended for any m-phase AC motor - induction, synchronous reluctance or synchronous permanent magnet. The resultant average electromagnetic torque is determined by superimposing the asynchronous torques and magnet braking torque effects.     

Analytical model for permanent magnet motors with surface mounted magnets

This paper presents an analytical method of modeling permanent magnet (PM) motors. The model is dependent only on geometrical and materials data which makes it suitable for insertion into design programs, avoiding long finite element analysis (FEA) calculations. The modeling procedure is based on the calculation of the air gap field density waveform at every time instant. The waveform is the solution of the Laplacian/quasi-Poissonian field equations in polar coordinates in the air gap and takes into account slotting. The model allows the rated performance calculation but also such effects as cogging torque, ripple torque, back-EMF form prediction, some of which are neglected in commonly used analytical models.     

Determination of NEMA Design Induction Motor Parameters From Manufacturer Data

This paper proposes a simple method of determining the equivalent circuit parameters of National Electrical Manufacturers Association (NEMA) design A and B types of induction motors from standard manufacturer data such as rated output power, starting torque, breakdown torque, and efficiency and power factor at rated output power. A set of nonlinear equations for various quantities is first derived from the equivalent circuit with a single-cage rotor model, and then, equate to the corresponding actual values supplied by the manufacturer. These equations are then solved using a least-squares based algorithm to determine the motor parameters. The rotor parameters are considered as slip dependent to predict the starting torque of the motor and that requires refining the breakdown torque equation as well as the slip at which the breakdown torque occurs. The proposed method of determining the motor parameters is then tested on more than 300 large-size HV induction motors. The effectiveness of the proposed method is evaluated by calculating various external quantities of the motors through the estimated parameters and comparing them with the corresponding actual values supplied by the manufacturer.      

Starting and Steady-State Characteristics of DC Motors Powered by Solar Cell Generators

The performance of dc motors (series, separately-excited, and shunt motors) powered by a solar cell generator and loaded by two different types of loads, one a constant load and one a ventilator load, were analyzed with respect to the transient (starting) and steady state operation. Direct current motors are employed in photovoltaic water pumping systems; therefore, the understanding of the system operation and the matching of the system components (solar cells, dc motor type, and load type) are important factors of the system design. Since the solar cell generator in a nonlinear and time-dependent power supply with an output that varies with the insolation (hourly and daily), the performance characteristics of the dc motor are different when supplied by a solar cell generator than when supplied by a conventional constant voltage source. The transient solution was obtained by using an available computer program - SUPER SCEPTRE. The separately - excited (or permanent magnet) motor with a ventilator load was found to be the most suitable for the solar cell generator. The series motor is quite acceptable, but the shunt motor gives poor performance. In all cases the ventilator load is more compatible with the solar cell generator than with the constant load.     

Control of a linear permanent magnet brushless DC motor via exactlinearization methods

The author develops a position controller for permanent magnet brushless DC motors (PMBDCMs) which systematically determines control laws for operation in both the transient and steady-state with consideration of reluctance force. The controller design is based on a differential geometric approach which assists the motor in overcoming its inherent deficiencies, such as effects of torque ripples and reluctance torque. This is achieved by transforming the nonlinear state equations into an exact linear model. Computer simulations of the resulting closed-loop system were performed to demonstrate the effectiveness of the proposed control laws. Simulation results of the control variables were injected into the actual nonlinear system in an experimental open-loop setup to validate the design procedure     

A direct torque-controlled interior permanent-magnet synchronous motor drive without a speed sensor

This paper reports results of further investigation of the so-called direct torque control (DTC) technique to an interior permanent magnet (IPM) synchronous motor drive. This torque control technique for IPM motors requires no dq-axes current controllers and coordinate transformation networks. A completely sensorless IPM motor drive with DTC, which uses a new speed estimator from the stator flux linkage vector and the torque angle, is presented. It is shown that including the torque angle in the estimation process results in a far more accurate transient speed estimator than what is reported in the existing literature.     

Estimation of induction motor double-cage model parameters from manufacturer data

This paper presents a numerical method for the estimation of induction motor double-cage model parameters from standard manufacturer data: full load mechanical power (rated power), full load reactive electrical power, breakdown torque, and starting current and torque. A model sensitivity analysis for the various electrical parameters shows that stator resistance is the least significant parameter. The nonlinear equations to be solved for the parameters determination are formulated as a minimization problem with restrictions. The method has been tested with 223 motors from different manufacturers, with an average value of the normalized residual error of 1.39/spl middot/10/sup -2/. The estimated parameters of these motors are graphically represented as a function of the rated power.     

Control-based reduction of pulsating torque for PMAC machines

Control methods in torque pulsating reduction for surface-mounted permanent magnet motors are discussed in this paper. The pulsating torque is a consequence of the nonsinusoidal flux-density distribution caused by the interaction of the rotor's permanent magnets with the changing stator reluctance. The proposed control method is estimator based. To assure parameter convergence, Lyapunov's direct method is used in estimator design for the flux Fourier's coefficients. A novel nonlinear torque controller based on flux/torque estimate is introduced to reduce the influence of the flux harmonics. The influence of the cogging torque is considerably reduced at lower motor speed using the internal model principle and adaptive feedforward compensation technique. The overall control scheme and experimental results are also presented     

The operation of permanent magnet DC motors powered by a commonsource of solar cells

In a photovoltaic water-pumping system, the solar cell array is usually designed to power a single motor-load pump. Several water-pumping systems of the same or different types that are in close proximity to each other can be powered by separate solar cell arrays (sources) for each one, or, alternatively, by a common solar cell source for all the water pumping systems. The authors introduce a procedure for comparing the performances of these two setups. One system includes a permanent magnet DC motor and a volumetric pump, and the other a permanent magnet DC motor and a centrifugal pump. The comparison was also done for the same systems when a maximum-power point tracker (MPPT) was included for both the separate and the common solar cell source. It is shown, for example, that in systems not including MPPTs the total performance of the two motor-pumps in the common source system is improved as compared to the performance of the two motor-pumps when they are powered separately by individual sources     

A new method for quality monitoring of induction motors

Catalog data of three-phase induction motors specify values of some operational parameters in addition to the nameplate information. These parameters include the efficiency, power factor, starting current, maximum torque, rated torque, and starting torque. At the end of the manufacturing process, extensive testing is required to ensure that a specific motor meets the specifications. In this paper, a method is presented to ensure that the motor meets the operational parameter specifications, including the tolerances that might be imposed using the results only of the no-load test and the blocked-rotor test     

A control scheme with performance prediction for a PV fed water pumping system

This paper focuses on modeling and performance predetermination of a photovoltaic (PV) system with a boost converter fed permanent magnet direct current (PMDC) motor-centrifugal pump load, taking the converter losses into account. Sizing is done based on the maximum power generated by the PV array at the average irradiation. Hence optimum sizing of the PV array for the given irradiation at the geographical location of interest is obtained using the predetermined values. The analysis presented here involves systems employing maximum power point tracking (MPPT) as they are more efficient than directly coupled systems. However, the voltage and power of the motor might rise above rated values for irradiations greater than the average when employing MPPT, hence a control scheme has been proposed to protect the PMDC motor from being damaged during these conditions. This control scheme appropriately chooses the optimum operating point of the system, ensuring long-term sustained operation. The numerical simulation of the system is performed in Matlab/Simulink and is validated with experimental results obtained from a 180 V, 0.5 hp PMDC motor coupled to a centrifugal pump. The operation of the system with the proposed control scheme is verified by varying the irradiation levels and the relevant results are presented.     

Accurate Prediction of Magnetic Field and Magnetic Forces in Permanent Magnet Motors Using an Analytical Solution

This paper presents an analytical model suitable for analyzing permanent magnet motors with slotted stator core. By including the effect of the interaction between the pole transitions and slot openings, the model is able to predict the airgap field and magnetic forces with high accuracy, which cannot be achieved using the previously available analytical methods. The results of electromagnetic forces, i.e., the cogging torque and unbalanced magnetic pull, computed analytically agree well with numerical simulations using the finite-element method. The model is used to analyze the magnetic forces developed in permanent magnet brushless motors when the design parameters vary in wide ranges. The model is useful in design and optimization of permanent magnet motors.      

基于模糊控制的新型永磁开关磁阻电机控制系统研究与设计

提出了一种新型永磁式开关磁阻电机。通过对传统电机结构上进行了改进,在定子上加入永磁材料,使得电机成为混合励磁电机,分析了其结构及原理等,并探讨了其调速方式,把模糊控制运用于调速系统,设计了其调速系统的软硬件,最后对其样机进行了试验,对开关磁阻电机的改进具有一定指导意义。     

旋转式力矩马达电液转换器的研究

本文推荐了一种用永磁直流伺服电动机作为力矩马达的电液转换器，永磁直流伺服电动机具有不易卡涩、成本低、安装调试方便等优点，通过仿真的这种电液转换器用于中小机组的DEH系统，是一种合理的选择。     

A novel high power density permanent magnet variable-speed motor

A novel polyphase, multipole, permanent magnet (PM) motor which possesses high power density, high efficiency and excellent controllability, yet can be produced by conventional fabrication techniques, is proposed. The basic operating principles, design features, performance analysis and control system are described. The experimental results for a 5 kW, 1500 RPM prototype PM motor and its comparison with other types of motors such as switched reluctance motors and induction motors are given. This motor also has superior dynamic performance     

Line start permanent magnet synchronous motors: Challenges and opportunities

Future energy challenges, likewise the environmental crises such as fossil fuel emissions and global warming urge the world to focus on energy saving programs more than ever. An effective way to face these challenges is to improve electric motors efficiency as one of the greatest energy consumption apparatuses in the world. Induction motors constitute, by far, the largest portion of electric motors both in terms of quantity and total power ratings among all electric motors. However, more efficient motor types gradually appear as alternatives. In this paper, line start permanent magnet motors as a powerful candidate with growing market are investigated in some details. The motor opportunities like high efficiency, high power factor and high power density are explored against the challenges associated with this motor including higher cost, extra manufacturing burden and transient and synchronization behaviors. Finally, some concluding comments and remarks are drawn for future research and manufacturing of line start permanent magnet motors.     

Performance of interior permanent magnet motor drive over widespeed range

This paper investigates the performance of an interior permanent magnet synchronous motor (IPMSM) drive over wide speed range for high precision industrial applications. The scheme incorporates the maximum torque per ampere (MTPA) operation in constant torque region and the flux-weakening operation in constant power region in order to expand the operating limits for an IPMSM. Improved mathematical expressions are derived to analyze the performances of the IPMSM. The power ratings of the motor and the inverter are considered. The effects of motor parameters particularly, the saliency ratio (X_q/X_d) on the voltage limit constraint and the power capability of the inverter are also investigated. The efficacy of the above mentioned drive system and the improved steady-state analysis are evaluated by both experimental and computer simulation results. The complete drive is implemented in real-time using digital signal processor (DSP) controller board DS 1102 on a laboratory 1 hp interior permanent magnet synchronous motor