抽油机用永磁同步电动机的研制及应用

针对目前永磁电动机在抽油机上使用存在的问题，我们联合研发了新一代适应抽油机工况的永磁电动机。本文介绍了抽油机用永磁同步电动机改进的创新点；通过室内、外试验，且与其他永磁电动机的比较证明了抽油机用永磁同步电动机的性能、特点都能满足抽油机的使用要求；在抽油机上使用具有很好的节能效果。     

Core loss in buried magnet permanent magnet synchronous motors

The steady-state core-loss characteristics of buried-magnet synchronous motors operating from a sinusoidal constant frequency voltage supply are investigated. Measured and calculated core loss, with constant shaft load, is shown to increase with decreasing terminal voltage due to an increase in armature reaction-induced stator flux-density time harmonics. Finite-element modeling is used to show that the additional loss due to the time-harmonic fields can increase core loss by a factor of six over the loss associated with only the fundamental component field at low motor flux levels. A simple air-gap model of motor flux components shows that this increased loss is due to localized rotor saturation. Thus, stator-core harmonic fields should be expected for all buried-magnet rotor synchronous motors (with or without a cage) operating at low flux levels. This factor becomes increasingly important when the motors are operated in the high-speed low-flux mode in conjunction with a variable-speed drive     

Transient performance of series connected three phase slip-ringinduction motors

The possibility of operating a three phase slip-ring induction motor as a series connected motor is explored. The merits and drawbacks of this mode of operation are discussed. For this purpose, the necessary mathematical models along with the corresponding computer simulation are developed and experimental verification of the theoretical results is also carried out. It has been found in general that operation of slip-ring induction motors as series connected motors is possible providing that the rotor winding is connected in a sequence opposite to that of the stator winding. This adds flexibility to the modes of operation of these motors. Moreover synchronous operation is also possible, providing that the series connected motor is driven initially at twice its synchronous speed and then connected to the supply     

Optimal efficiency control strategy for interior permanent-magnet synchronous motor drives

In this paper, the problem of efficiency optimization in vector-controlled interior permanent-magnet (PM) synchronous motor drives is investigated. A loss model controller is introduced that determines the optimal d-axis component of the stator current that minimizes power losses. For the implementation of the suggested controller, the knowledge of the loss model is not required since an experimental procedure is followed to determine its parameters. Furthermore, it is shown that the loss model of the interior PM motor can be used as a basis for deriving loss minimization conditions for surface PM synchronous motors and synchronous reluctance motors as well. Experimental results of an interior PM motor are presented to validate the effectiveness of the proposed method and demonstrate the operational improvements.     

Modeling and analysis of variable speed single phase induction motors with iron loss

Despite their usual low power ratings of single phase induction motors, they consume a considerable part of total motors energy consumption due to their large and ever-increasing quantity. The recent rising of oil prices and environmental crises has fortified the idea of energy saving practices in all applications; particularly in single phase induction motors due to their typical low efficiency. An essential requirement for this practice is the modeling and analysis of machine electrical losses under variable frequency operation. In this paper an improved steady state model of single phase induction motors is derived to investigate major motor characteristics like torque–speed, input power, output power, etc. A special emphasis is placed on accurately representing core losses at variable frequency. The winding currents phase difference is reintroduced as a fundamental motor variable to determine motor performances including losses and efficiency. An advanced computerized motor test setup is designed and built for on-line measurement of motor characteristics at different supply and operating conditions. The extensive experimental results, in good agreement with the simulation results based on the mentioned analysis, confirm the validity of the proposed model.     

Calculation of neutral voltage shift in LCI driven induction motors

Load commutated inverter (LCI) drives are being used for adjustable speed control of induction motors and synchronous motors. It has been found that the motors and transformers connected to these drives are subjected to higher than normal voltage stresses to ground and premature failures of motors have been reported. This has been shown to be due to a voltage difference between the source side neutral voltage and the motor neutral voltage. This voltage is known as the neutral shift. This neutral shift voltage is added to the normal line to neutral or phase voltage causing a much higher than normal line or terminal to ground voltage stress in the ungrounded side of any DC linked AC converter. Voltages as high as 3.3 pu normal phase voltage may be seen for certain types of inverters. A method of determining the neutral shift voltage is presented. Results of a computer simulation of an LCI circuit and test results are presented to verify this analysis     

The Use of Partial Discharge and Impulse Voltage Testing in the Evaluation of Interturn Insulation Failure of Large Motors

Several 13.2 kV, 21,000 HP synchronous motors failed as a result of interturn insulation breakdown. Investigation of motor failures indicated that the cause was related to high magnitude, steep fronted surge waves (References 1 and 2). Partial discharge (corona) related failures were discounted without any actual measurements. To confirm the validity of the previous investigation, partial discharge testing was conducted on four new 21,000 HP motors and on one failed 21,000 HP motor. Additionally, surge impulse testing was performed on the failed motor to assess interturn insulation endurance. This paper presents the results of above tests. It is concluded that failure of motors could not be caused by corona, Confirmation of previous investigation results indicated that partial discharge testing can be used as a diagnostic tool in the evaluation of interturn insulation of large motor.     

Average-Value Modeling of Brushless DC Motors With 120° Voltage Source Inverter

This paper describes average-value modeling of brushless dc (BLDC) motor-inverter systems, which is challenging due to the complicated switching patterns of the stator currents. A new average-value model (AVM) that appropriately includes commutation and conduction subintervals of the BLDC motor with a 120deg inverter is presented. The proposed model is explicit and uses a proper qd model of the permanent magnet synchronous machine. The required commutation angle is represented as a nonlinear algebraic function, which is readily obtained from the detailed simulation. The studies conducted are based on two typical industrial motors with different electrical time constants, and include hardware measurements, detailed simulation, and comparison with a previously published AVM. The proposed model is shown to be more accurate in terms of both large and small-signal analysis and is applicable to both types of motors.     

Transient Modeling and Parameter Estimation of Field Aligned Starting

Field aligned starting (FAS) is a new technique for starting three-phase cage induction motors on single-phase supply lines with minimal inrush currents. It uses a simple energy storage system to generate a very high impulsive torque by which the motor is started before being connected to the mains supply. The spinning motor can then be connected to the mains to operate in a standard Steinmetz connection without incurring high inrush currents, if the moment of mains connection is properly timed. This paper presents a transient model and an accompanying parameter estimation method through which the transient behavior of three-phase induction motors operated with FAS can be analyzed. The proposed model is based on instantaneous symmetrical components and is used to investigate a 3 kW motor started under various operating conditions. The proposed parameter estimation method and the developed transient model are both validated by experimental results.     

Coupling a dynein transport model with a model of anterograde and retrograde transport of intracellular organelles

A model of fast axonal transport of organelles that accounts for dynein transport in an inactive state toward the axonal synapse is developed. It is assumed that anterograde transport of inactive dynein in an axon is powered by kinesin motors. It is further assumed that the probability of organelle attachment to a dynein motor is directly proportional to the concentration of free dynein motors available at a particular location in the axon. The results predicted by two models (the first one is that which incorporates dynein transport and the second one is the traditional model that does not incorporate dynein transport) are compared. The obtained results suggest that the availability of dynein motors in a particular location in an axon can be a factor limiting fast axonal transport.     

Starting transients of three phase synchronous motors connected toa single phase supply

Balanced operation of three phase synchronous motors have been dealt with extensively in the literature. However, unbalanced operation has not received as much attention. One of the interesting unbalanced modes of these motors is their operation from a single phase supply. Such a mode of operation can be of special importance in remote areas where only single phase supply is available or in the case of an open circuited single line fault. In this paper, the possibility of operating three phase synchronous motors from a single phase supply through the use of a phase balancer capacitor is explored. The criteria for selecting the required phase balancer capacitor is presented and the analysis of the behaviour of such motors during the starting process is carried out. For this purpose, a rigorous state space mathematical model has been developed. The validity of this model have been verified experimentally     

Speed Control System for Brushless Cascade Induction Motors in Control Range of Slips s1>1 and S2>1

This paper describes principles together with analytical and experimental studies of a speed control system for brushless induction motors of cascade connection in the control range of the slips s1> 1 and s2>1 which was devised by one of the authors. Steady state analyses of the performances of the motor control system are discussed, and results of the tests are presented. It is found that the motor can be controlled widely and comparatively efficiently by controlling the converters which are connected electrically to one of the stator windings of the two motors.     

Methods for determining the intermediate-axis saturation Characteristics of salient-pole synchronous Machines from the measured D-axis Characteristics

In the analysis of the steady-state performances of saturated synchronous machines using the classical two-axis (d- and q-axis) frame model, the accurate calculation of the machine performances depends to a large extent on their saturation conditions. However, the effect of saturation depends not only on the saturation level in the axis of the resultant machine ampere-turns (intermediate-axis) but also on the phase angle between the resultant ampere-turns and the resultant magnetic flux. This work presents four analytical methods for determining the intermediate-axis saturation characteristics of salient-pole synchronous machines from the measured d-axis saturation characteristics. The accuracies of these four methods have been verified by comparing the measured field currents and load angles of two laboratory salient-pole synchronous machines of different designs with those calculated using an innovated approach which uses the intermediate-axis saturation characteristics directly in the modeling of the saturated synchronous machines. Moreover, the calculated intermediate-axis saturation characteristics have been compared with the measurable ones in the case of one of these machines.     

Matching of DC motors to photovoltaic generators for maximum dailygross mechanical energy

The matching to solar-cell generators of both separately excited and series DC motors driving pumping loads is addressed. It is shown that the maximum gross mechanical power can be obtained at slightly higher voltages and slightly lower currents compared to the maximum electrical-power points on the solar-cell generator characteristics at different insolation levels. Guidelines for constructing the loci of the motor voltage-current points for maximum mechanical power and for determining the optimal motor parameters to match the solar generator are derived in terms of the mechanical load characteristics and the solar array parameters. Results of applying these design criteria to practical case studies enabled the assessment and comparison of both kinds of motors, especially as far as the daily utilizable output mechanical energy is concerned. The superiority of the separately excited motors in such systems is quantitatively indicated. The results are also compared to corresponding information available in the literature     

Field test of motor efficiency and load changes through air-gaptorque

Although air-gap torque equations have been known for several decades, this is the first known paper suggesting the use of air-gap torque to measure efficiency and load changes of electric motors in the field. Very few assumed values are required, and the method is applicable for induction motors as well as brushless-DC adjustable-speed and synchronous motors. Theoretical foundation for this proposed method is presented. Experiments conducted on an adjustable-speed motor show the validity and potential of this approach     

Harmonic reduction in adjustable-speed synchronous motors

Adjustable-speed synchronous motors (ASSM) are very popular in high-power high-speed applications. The Chilean mining industry uses them in milling operations in ranges of several thousands hp. Although a high pulse number for the inverter would be beneficial, it never goes beyond 12, due to complicated connections. Thus, a distorted harmonic-rich current feeds the synchronous motor, increasing the inverter commutation angle and causing additional rotor-heating and pulsating electric torque. Harmonic suppression by filters is not viable due to the variable frequency nature of the motor. In this paper, a new design for the inverter, without complicated circuitry, is proposed, so that it works with 36 pulses and then the motor is fed with a highly sinusoidal current. Also, the same technique is applied to the rectifier end, so that an effective harmonic reduction is carried out at both ends of the system, i.e., the motor as well as the AC supply system. A 20 kVA laboratory development drive system has been built and experimental waveforms for the conventional (12-pulse) and proposed (36-pulse) configurations are included     

基于ANFIS-PI的同步磁阻电机矢量控制

针对同步磁阻电机在正常运行过程中磁路饱和导致的电感变化问题,提出一种采用自适应神经模糊推理系统(ANFIS)的PI参数整定方法,以提高电机控制的响应速度。先采用电流调节系统对样机有限元模型进行仿真,得到电流电感数据并拟合电感表达式,进而计算最大转矩电流比的电流角,然后搭建了基于ANFIS-PI的同步磁阻电机矢量控制模型,将经过神经网络训练后的控制模型与有限元软件进行联合仿真。结果表明,与常规PI控制相比,采用ANFIS-PI法可更准确地调整PI参数,进而提高电机动态响应速度。     

弯游梁抽油机与低转差电机的优化匹配仿真对比分析

针对大庆九厂油田的井况特点,以弯游梁式抽油机、永磁系列电机和双速双功率电机为对象,建立相应的有杆抽油系统的数学模型,在此模型基础上,从仿真的角度出发,讨论弯游梁式抽油机与两种节能电机的优化选配问题,为弯游梁抽油机与节能电机的合理选配提供了理论依据和解决方法。     

An improved model for saturated salient pole synchronous motors

An improved model for the transient analysis of saturated salient pole synchronous motors is presented. With the aid of saturation factors obtained by test or with finite elements, Park's equations for a synchronous machine are modified to independently account for the saturation of the magnetizing flux linkages in the region of the stator teeth and rotor pole face as well as saturation of the total flux linking the stator core. The model is used to calculate the starting performance for a direct online start as well as the transient performance during a load change. The model shows improvement over more traditional models, indicating that representation of both main flux and core saturation are important for synchronous machine analysis     

Characterization of coil faults in an axial flux variable reluctance PM motor

Variable-reluctance (VR) and switch-reluctance (SR) motors have been proposed for use in applications requiring a degree of fault tolerance. A range of topologies, of brushless SR and VR permanent-magnet (PM) motors are not susceptible to some types of faults, such as phase-to-phase shorts, and can often continue to function in the presence of other faults. In particular, coil-winding faults in a single stator coil may have relatively little effect on motor performance but may affect overall motor reliability, availability, and longevity. It is important to distinguish between and characterize various winding faults for maintenance and diagnostic purposes. These fault characterization and analysis results are a necessary first step in the process of motor fault detection and diagnosis for this motor topology. This paper examines rotor velocity damping due to stator winding turn-to-turn short faults in a fault-tolerant axial flux VR PM motor. In this type of motor, turn-to-turn shorts, due to insulation failures, have similar I-V characteristics as coil faults resulting from other problems, such as faulty maintenance or damage due to impact. In order to investigate the effects of these coil faults, a prototype axial flux VR PM motor was constructed. The motor was equipped with experimental fault simulation stator windings capable of simulating these and other types of stator winding faults. This paper focuses on two common types of winding faults and their effects on rotor velocity in this type of motor.