The impact of winding type on overvoltages in an induction motor operating with a frequency converter

A technique for calculation of wave parameters and overvoltages in one- and two-layer windings of an induction motor powered by a pulse-width modulation converter is introduced. A mathematical model and simulation results for wave processes in these windings are presented.     

Damping circuit to suppress motor terminal overvoltage and ringingin PWM inverter-fed AC motor drive systems with long motor leads

This paper proposes an equivalent circuit analysis to suppress overvoltage and ringing in pulsewidth modulation inverter-fed ac motor drive systems where long motor leads are required. Conventional analysis of the phenomenon is based on voltage reflection theory for the terminal end of the long cable. The authors implemented another analytical method using equivalent lumped L and C of the cable, and a transfer function for the equivalent circuit with a simple damping circuit, C-R or L-R damping circuit constants are determined from the nonoscillatory condition of the transfer function. Digital simulations and experiments are used to verify that a simple damping circuit can satisfactorily suppress overvoltage and ringing in a drive system with a long cable, such as a 100-m cable     

Results of an investigation on the overvoltages due to a vacuumcircuit-breaker when switching an HV motor

The results of a study of overvoltages arising when an HV motor is switched by a vacuum circuit breaker are presented. A laboratory test circuit was devised that would reproduce the actual network conditions in a generating plant, and special measurement and acquisition systems were used to enable the switching-surge amplitude and waveform to be recorded with accuracy. Statistical processing of the data was followed by estimation of the probability of occurrence of overvoltages and by evaluation of the number of the surges impinging on the motor-winding during its operating life. The results are discussed, and a number of conclusions are drawn     

Wavelength constants and interturn overvoltages in a multiturn random winding of an induction motor supplied from a PWM converter

A calculation procedure for wavelength constants and interturn overvoltages in a multiturn random winding of an induction motor supplied from a frequency converter is described. A mathematical model and modeling results for wave processes in sections (turns) of the multiturn random winding of the induction motor with a cage rotor are presented.     

AC motor drive systems with a reduced-switch-count converter

This paper presents two reduced-switch-count AC drive systems. One of the configurations was conceived to operate with a two-phase motor and the other one with a three-phase motor. The drive systems provide both bidirectional power flow and power factor control. Pulsewidth modulation techniques for the converter control are discussed. Experimental results are presented.     

Theory and operation of a four-quadrant switched reluctance motor drive with a single controllable switch-the lowest cost four-quadrant brushless motor drive

Low-cost motor drives are being sought for high-volume energy-efficient home appliances. Key to the realization of such low-cost motor drives is the reduction of the power electronic converter to the barest in terms of its components, particularly the active devices, finding the motor with the least complexity for manufacturing and a controller that can extract the desired performance from the machine and converter combination. These and other factors such as self-starting, speed control over a wide range, and, most of all, the crowning aspect of four-quadrant operation with a bare minimum number of controllable switches remain as formidable challenges for low-cost motor drive realization. An innovative four-quadrant switched reluctance motor (SRM) drive with only one controllable switch is realized in this paper, for the first time, in the opinion of the authors. The motor drive is realized using a two-phase machine and a single controllable switch converter. The theory and operation of the proposed four-quadrant SRM drive with the proposed control algorithm for its realization are described. The motor drive is modeled, simulated, and analyzed to verify its feasibility for self-starting, speed control, and for four-quadrant operation, and the simulation results are presented. Experimental results confirm the validity of the proposed control algorithm for four-quadrant control of the SRM drive. The focus of the paper is mainly directed toward the control algorithm for realizing the four-quadrant operation of the two-phase SRM drive with a single controllable switch converter.     

Compensation for the radial forces in an electric motor drive with a field-regulated reluctance machine

Ways to reduce radial loads on the bearings of electric machines with an electric traction drive are considered. An idea of compensation for radial loads is proposed, and a mathematical model of the electric motor drive with the controlled radial forces in the vertical direction is developed on the basis of a field-regulated reluctance machine. The model takes into account the influence of the vertical forces that are generated by various machine windings and wear in the mechanical part of the electric motor. Additional winding is used to appropriately assess the influence of the radial force. The maximum vertical force acting on the machine is calculated from the obtained waveforms. This fact allowed us to identify the future direction of research. Methods of mathematical modeling construct the dependence of the vertical force from the currents flowing in the windings of the electric machine. The minimum force is created when the field current changes, and the maximum force is created when the armature circuit current is varied. This indicates that the winding provides maximum compensation for the radial force.     

Self-tuning control of a switched-reluctance motor drive with shaftposition sensor

The control of the switched-reluctance motor (SRM) is usually based on the inductance profiles as a function of position. This paper addresses the problem of obtaining optimal performance from an SRM in the presence of parameter variation, which can alter the phase inductance profiles. The operation of an SRM drive in the controlled current mode from zero to base speed is considered. New self-tuning algorithms are presented which optimize the steady-state performance of the drive as measured by torque per ampere (TPA). Computer simulations are employed to show the existence and uniqueness of a solution to the optimal TPA problem. The application of the new control strategy is explained in the content of a speed controlled drive system. Experimental results are provided to demonstrate the validity of the self-tuning controller     

PM brushless DC motor drive with a new power-converter topology

With the growing potential for widespread use of permanent magnet brushless DC motor (PMBDC) drives in many low-cost applications, such as HVAC, refrigerators, and freezers in houses and small-velocity servos in process industries, it has become important to minimize the cost. One obvious place for cost reduction is in the cost of the inverter and its associated controller. With that perspective, a novel application of the converter topology for the PMBDC known as “C dump” in switched reluctance motor drives is proposed in this paper. The advantages and disadvantages of this topology vis-a-vis the conventional three-phase H-bridge converter, are highlighted from the points of view of economy in switches, volt-ampere rating, associated controller cost, and packaging. Design considerations for the PMBDC are derived for use with the proposed converter topology. The operational and design characteristics of this converter-driven PMBDC drive are derived for four-quadrant performance. Guidelines for the design of the proposed topology are derived, and presented in the paper. Experimental results from a laboratory prototype are presented to validate the feasibility of the proposed PMBDC drive system     

Mechanism analysis and output characteristics experiments of an ultrasonic motor with circumferential surface drive

A kind of ultrasonic motor, whose rotor is driven by stator’s inner circumferential surface, has been designed and fabricated. The paper has analyzed the stator deformation characteristics under bending mode by using finite element method, identified the motor’s working mechanism with two-phase voltage drive, and studied the different functions of tangential and radial displacements of the stator’s inner circumference small teeth under bending mode and pointed that the above mentioned displacements along two directions of small teeth could drive the rotor continuously with single-phase voltage. The paper has discussed the motor’s rotary direction reversing and put forward a concrete scheme of reversing with single-phase voltage drive. The mode of the stator was obtained by experiment. Under two-phase and single-phase voltages, running experiments of the motor have been accomplished and the corresponding characteristics curves have been drawn. Taken above analysis result as driving mechanism, a kind of thin-type standing ultrasonic motor can be developed further.     

Optimization of a variable-frequency induction motor drive with a scalar control system

The structure of an upgraded frequency control system and procedures for calculating control laws for induction motor drives under static and dynamic conditions are considered. The results of mathematical simulation and experimental investigation of the processes in a standard and an upgraded scalar control system are discussed.     

Indirect determination of the displacement components in an electric motor drive

High technological process quality requires the use of deviation closed-loop systems and the formation of appropriate informational support for a control process. The article discusses two approaches to obtaining information on displacement components: direct measurement of speed and/or position with the help of a sensor on the motor shaft and indirect determination of the object state vector using the available variables for the direct measurement without the shaft sensor (current and voltage). The main disadvantages of optical encoders are identified. An overview, a classification, a comparative analysis, and the ranges of application of indirect methods of determining displacement components are given (calculation for a model of an electric machine with the measurement of current and voltage of the stator and calculation of the static functional dependence).     

Research on a direct torque control for an electrically excited synchronous motor drive with low ripple in flux and torque

The electrically excited synchronous motor (ESM) has typically small synchronous inductance values and quite low transient values because of the damper windings mounted on the rotor. Therefore, the torque and stator flux linkage ripples are high in the direct torque control (DTC) drive of the ESM with a torque and flux linkage hysteresis controller (basic DTC). A DTC scheme with space vector modulation (SVM) for the ESM was investigated in this paper. It is based on the compensation of the stator flux linkage vector error using the space vector modulation in order to decrease the torque and flux linkage ripples and produce fixed switching frequency under the principle that the torque is controlled by the torque angle in the ESM. Compared with the basic DTC, the results of the simulation and experiment show that the torque and flux linkage ripples are reduced, the maximum current value is decreased during the startup, and the current distortion is much smaller in the steady-state under the SVM-DTC. The field-weakening control is incorporated with the SVM-DTC successfully. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2006, 26(7): 152–157 [译自: 中国电机工程学报]     

Improvement of motor design for a synchronous drive of an automation system in nuclear-power plants

The condition and prospects of development of special electrical machinery intended to replace regulating units in automatic-control systems of nuclear-power plants are considered. Technical solutions to ensure the operation of such machines in a controlled self-running regime are proposed. Two different methods of motor design are described in relation to the type of actuator: on the basis of electromagnetic loads and on the basis of the ratio of the moments of inertia of the motor and drive. Variants with different ratios of copper to steel parts are analyzed, and the conclusion is drawn that it is necessary to coordinate this relation with the size and weight requirements and overload capacity.     

Examination and location of partial discharge sites in severelyaged underground distribution cables

This paper presents the results of laboratory investigations of partial discharge (PD) in field aged XLPE underground power cables. PD measurements were made on sixty-one cable samples over a three year period. When PD was detected, the magnitude was measured and a site location was determined. PD site locations were predicted using time delay estimations between PD pulses arriving at opposite ends of the test cable. Fourteen of the samples tested had detectable levels of PD. Some of these PD sites extinguished during the measurement period and were returned to rated voltage aging. When samples had continuously active PD sites, they were either dissected or returned to the aging test. Four sites of this type were found allowing two for dissection and two for aging. Seven of the samples failed after PD measurements. All seven failed near the predicted PD location. During the PD testing, no test cables contained PD which initiated at or below operating voltage. When PD detection equipment was monitoring cables which failed, the failures occurred from 2 to 80 minutes after the presence of PD pulses was detected     

High-performance speed-sensorless control of an induction motor drive using a minimalist single-phase PWM converter

Home appliances and comfort conditioners are yet to benefit from the recent developments in power electronics because of cost constraints. In this paper, a speed-sensorless induction motor drive system using converters with reduced device counts (minimalist, sparse converters) and actuated from a single-phase system is proposed for such low-cost applications. The analysis, control, dynamic, and steady-state characteristics of the proposed drive are experimentally illustrated.     

Identification of the machine parameters in a vector-controlledinduction motor drive

High dynamic performance of pulse-width-modulated (PWM) inverter-fed induction motor drives was achieved by using the method of field-oriented control. This method requires the actual value of the rotor time constant as essential system information, based on how the magnitude and the position of the rotor flux are calculated. An online identification technique for the rotor time constant and for other machine parameters is described. The identification is based on an evaluation of the stator current trajectory, which is the dynamic response of the induction motor to the PWM-switching sequence. An analytical machine model is operated in parallel to the actual machine, having the stator voltages and the mechanical speed of the induction motor as input signals. The coincidence of the two stator current trajectories of the model and the machine serves as an error indicator for the parameter identification scheme, permitting repetitive updates of the model parameters     

EMI characterization and simulation with parasitic models for a low-voltage high-current AC motor drive

In this paper, a 12-V 1-kW permanent-magnet ac motor drive is tested extensively at a wide frequency range, and the frequency spectra are partitioned for identification of noise sources and their propagation paths. Switching characterization of the power MOSFET and its body diode reverse-recovery characterization are evaluated for circuit modeling. The parasitic components and common mode path are identified and measured with the time-domain reflectometry (TDR) method. The inverter circuit model is then constructed with major parasitic inductance and capacitance in device modules, passive components, leads, and interconnects. To verify the validity of the inverter model, a comparative study is performed with computer simulations and hardware experiments. The fundamental mechanisms by which the electromagnetic interference (EMI) noises are excited and propagated are analyzed, and the significant roles of parasitic elements coupling with device switching dynamics in EMI generation are examined. The results indicate that the identification of parasitic inductance through TDR measurement helps verify the voltage spike during turn-off, or vice versa. The conducted EMI noise caused by parasitic components of bus capacitor, dc bus, and devices is proven to be identifiable with the characterization and simulation techniques used in this paper.