High-voltage Motor Research Articles

Optimization of Magnetic Flux-path Design for Reduction of Shaft Voltage in IPM-Type BLDC Motor

In this paper, we propose a method for suppressing shaft voltage by modifying the rotor shape and the permanent magnets in interior permanent magnet type high voltage motors. The shaft voltage, which adversely affects the bearing by occurring bearing current, is induced by parasitic components and the leakage flux in motor-driven systems as well as inherent linkage flux between main magnetic flux and shaft according to rotor configuration. Thus, shaft voltage should be analyzed and considered under inverter-driven and non-inverter-driven conditions because inherent linkage flux can analyze under non-inverter-driven condition. In this study, we designed re-arrangement magnet and re-structuring rotor to minimize the shaft voltage. In addition, we optimized the proposed models. The shaft voltage suppression effect of the designed model was validated experimentally and by comparative finite element analysis.

Research on Motor Relay Protection of High-Voltage Variable Frequency Motor Drive System

Abstract – This paper regards motor differential protection and single phase grounding protection. Firstly, this paper introduces the traditional principle and setting methods of them, and points out that the traditional relay protection device is no longer applicable under the situation of high-voltage variable frequency motor driver applications. Secondly, according to the feature that variable frequency driver runs between 0 Hz to 50 Hz, the paper analyzes the characteristics of voltage and current waveforms at different frequencies when inter-phase short circuit or single-phase grounding occurs. Based on the analyses above, the paper goes a step further to study the configuration program and setting methods of differential protection and single phase grounding protection in the situation of the high-voltage inverter drive occasions.

Black-Out Test Versus UV Camera for Corona Inspection of HV Motor Stator Endwindings

As part of a factory acceptance test program for high-voltage (HV) motors, end users sometimes specify a black-out test. This is a traditional offline inspection where the stator is placed in complete darkness, each phase is energized to 115% of rated line-to-neutral voltage, and both ends of the stator are observed to determine the presence, location, and severity of endwinding surface partial discharges (PDs). The setup for the test may be complex and risky due to the need for observers to be standing in darkness close to the energized parts of the stator. The test results are qualitative and strongly depend on the observer's eyesight and individual perception. A safer and more accurate alternative is to use an ultraviolet (UV) camera or viewer. The observed PD activity may be observed in ambient lighting, recorded, and quantified through simultaneous offline PD measurements. This paper describes the two inspection techniques and presents experimental validation of the UV corona camera inspection method as a suitable replacement for a black-out test. Sample 13.8-kV coils were wound in a fixture simulating their relationship in a stator winding and subjected to high-potential tests while observed under black-out conditions and with a UV corona camera in ambient lighting. The stator windings from two HV compressor motors were inspected using the same camera. Recorded images of the observed discharges and measured PD activity in the sample coils and stator winding were used to compare the evaluation by each test method.

A Dynamic Reactive Power Compensation Method of Super High-Power and High-Voltage Motor

According to the low power factor and low running efficiency, a dynamic reactive power compensation method of the super high-power and high-voltage motor is proposed in this paper. The following works have been done in the study: topology of the dynamic reactive power compensation device; principle of the dynamic reactive power compensation method; control system of the dynamic reactive power compensation device; implementation of the dynamic reactive power compensation method. The amount of reactive power compensation can be adjusted smoothly and dynamically in the process of the super high-power and high-voltage motor soft-starting. The research of this paper has laid a theoretical foundation for this compensator in industrial applications. The novel design is characterized by flexible parameter setting, excellent soft starting performance of the super high-power and high-voltage motor and bright prospect in application.

FE analysis of current displacement phenomena in a squirrel cage motor working at cryogenic temperature

Abstract The paper presents the special software for transient FE analysis of coupled electromagnetic-thermal problems in a squirrel cage submerged motor working at cryogenic temperature. A time-stepping finite element method and transients analysis of an induction motor has been applied. The non-linearity of the magnetic circuit, the movement of the rotor, skewed slots, and the influence of temperature on electric and thermal properties of the materials has been taken into account. Developed on the basis of presented algorithm a computer program used to analyze the phenomenon of current displacement in the rotor bars of high-voltage cage induction motor working in cryogenic conditions. The results of the simulations are presented.

Engineering calculation of dynamic impedances and starting characteristics for high-voltage induction motors

Starting characteristics and dynamic impedances are the key parameters for the research of high-voltage induction motor. The measurement of starting characteristics and dynamic impedances for high-voltage induction motors can present problems for both manufacturers and users, so a practical and feasible calculation method is necessary. In order to facilitate the engineering application, this paper presents a set of useful calculation method for motor transient torque, current, and impedances. In the calculation, the influence of dynamic characteristics and impedances on each other, which are often neglected in previous calculation, is considered. So the influence of impedances on the characteristic curves can be analyzed more accurately using this method. Based on the earlier analyses, this paper further studies the influence of different start-up voltages on the stator leakage reactance. Finally, through the analysis and calculation results of many motors, it can be verified that only when the relation between starting characteristics and dynamic impedances is considered in calculation process will the results be better in line with the actual value. The algorithm is suitable for engineering use. Copyright © 2014 John Wiley & Sons, Ltd.

Motor soft starters in electric drives used in mining machinery

This paper analyzes the selection of the type of a starter for electric drives with high-voltage synchronous motors depending on the nature of the change in the load torque of the mechanism, the amount of driving synchronous motors to be started up (single motor or successive start of several motors), and the technological regime requirements, as well as the parameters of the synchronous motor. Single-line schemes of implementing the soft starters of driving high-voltage synchronous motors of large grinding machines and axial mine fans for main and auxiliary ventilation are given.

Оптимизация работы технологически связанных электроприводов газоперекачивающих агрегатов компрессорных станций

The flow diagram of electrically driven compressor station of the main gas pipelines with high-voltage MW electric motors is considered. The complex analysis of features of group parallel engaging of units on a uniform main pipeline is presented. It is shown that characteristics mismatch of centrifugal superchargers and electric motors causes load distribution irregularity between units with the raised electric power consumption. Methods of loads matching within the limits of work of technologically interconnected electric drives by means of frequency converters are suggested. Examples of group of units control algorithms within the limits of dual-purpose electrically driven compressor station and results of the numerical analysis of comparative effectiveness of frequency converters application are presented. It is shown that with increase of gas supply control range from 5 to 10 % the economy of the consumed electric power also increases from 1,05 to 1,74 MW. The optimality criterion of technologically interconnected electric drives of gas compressor units in the form of multifactorial quality functional is suggested. Practical recommendations for optimization of power consumption of the most widespread machines STD-4000 and STD-125000 in the electric drive of gas compressor units and prospects of their development are given.

High-Voltage Three-Phase Asynchronous Motor Soft-Starter via Hyristor for Water Cooling System of Steel Mill

This article introduces a high-voltage three-phase asynchronous motor soft-starter via thyristor that is suitable for water cooling system of steel mill. It improves motor start and stop characteristics, effectively eliminates water-hammer" effect caused by traditional direct start and stop, and is making more and more important positive impacts in the water cooling system of steel mill.

Problems structure-parametric optimization of oil pipelines by frequency-regulated electric drive

In recent years, much attention is paid to the development of variable frequency drive (frequency-adjustable electric drive) for pumps of pipeline transport of oil. One of the most important problems that must be addressed during the optimization of the technological process of pumping using frequency-adjustable electric drive is the choice of the number of pumps, frequency converters and electric motors rotation speed. In the article the objectives and criteria of optimization of pumping oil by pipeline with frequency-regulated drive the pumps are discussed. For drives of main pump for pumping stations are used high-voltage electric motors. Each motor together with the pump can be switched on or off, and each motor can be powered directly from the network or from the frequency converter. While there are many possible structures as each of pump stations and technological area as a whole, with different number and combination included pumps, motors and frequency converters. In the modern system of pumping out «from the pump in the pump» mode all pumps technological area of interrelated. Changing the mode of one of the pumps changes the mode of pumping technological area, and, consequently, regimes of all other pumps. The modes of operation of all the pumps, motors and frequency converters of all pump stations technological area are interrelated. Therefore, when optimizing the process of pumping motors, frequency converters and pumps should be regarded as components of a single process. Thus, related how the composition of a component technological area and modes of their work. Therefore optimization of pumping oil is advisable to use structural-parametric optimization, which is a combination of structural and parametric optimization. Structural optimization using frequency-adjustable electric drive is the determination of the optimal number and combination included in regulated and non-regulated pumps. Parametric optimization when using a frequency regulation lies in selecting the optimal speed of rotation of each of the pumps. All criteria of optimization of modes pipeline using frequency-adjustable electric drive proposed to divide into three groups: energy criteria, the purpose of which - reduction of energy costs for pumping, technological criteria, the purpose of which is the optimization of technological parameters and to increase reliability, and operational criteria, which purpose is to reduce the cost of maintenance and repair of objects of the main pipeline. A block diagram of the structural and parametric optimization of the technological process of pumping with two contours optimization is offered. In the contours of the structural and parametric optimization the same or different criteria optimization can be used. The principles of selection criteria optimization are proposed.

Fortifying Subsea Wells: A Comparative Analysis of Mainwall Insulation Materials Used in Natural Gas Production

Natural gas recovery from subsea wells is increased by an artificial lift, which can be provided by a compressor installed at the wellheads. Such a machine is driven by a high-speed, high-voltage electrical motor that is integrated into the same casing as the compressor. The motor is cooled by the process gas bled from the compressor itself. Because the insulation system is in direct contact with the process gas, it must have good chemical resistance and high mechanical strength to withstand the environment.

Differential Protection for High-Voltage Variable Frequency Motor Based on Sampled Values Algorithm

With the application of inverter in high-voltage motor, the traditional current differential protection cant be used because of the variable frequency. So it adopts low sensitive current instantaneous protection as main protection, which doesnt meet the security standard of grid state. In order to improve the sensitivity and reliability of high-voltage motor protection, a new method based on current sampled values is proposed in this paper, which adapts to the variable frequency system. After a brief description about the impact of inverter on main protection of motors, it introduces the principle of sampled value current differential protection and variable RS sampled value algorithm. A matlab example is used to simulate. On the whole, the simulation and analysis of the calculation results verify the feasibility and reasonableness of the method. Therefore, it provides a new approach for the protection of high-voltage motor in variable frequency system.

Suppression of Shaft Voltage by Rotor and Magnet Shape Design of IPM-Type High Voltage Motor

In this paper, we propose a method for suppressing shaft voltage by modifying the shape of the rotor and the permanent magnets in interior permanent magnet-type-high-voltage motors. Shaft voltage, which is induced by parasitic components and the leakage flux in motor-driven systems, adversely affects their bearings. In order to minimize shaft voltage, we designed a magnet re- arrangement and rotor re-structuring of the motor. The shaft voltage suppression effect of the designed model was confirmed experimentally and by comparative finite element analysis.

Calculation for the Heating and Safe Operation Time of YKK Series High-voltage Motors in Starting Process

In order to analyze the heating and cooling conditions of high voltage motors of YKK series in starting process, the starting characteristics and ventilation systems are calculated. The starting characteristics calculation method is improved and compared with the static characteristic, dynamic characteristics come to more consistent with the actual situation. The calculation result of heating is more accurate according to the calculation of dynamic characteristics. A windresistance network model is built combined with the motor cooling structure to calculate the distribution of air flow in the motor. The locked-rotor safety running time in starting process is calculated based on the accurate calculation of heating and cooling condition. The result is more close to the experiment and it has an important significance to the design and improvement of YKK series high voltage motor.

Analysis of Water Friction Loss and Calculation of Rotor 3D Temperature Field for Wet Submersible Motor

The water friction which is produced in the high-voltage wet submersible motor is much more than that of General motor, and it plays an important role in total consumption of motor. It is difficult to calculate the consumption of water friction. In order to study the high-voltage wet submersible motor water friction loss and temperature field distribution more accurately, this paper take the 6kV-3150kW motor as an example. Based on the Fluid Theory and the Heat Transfer Theory, it establishes the model of the loss of water friction and rotor temperature field. At last, the finite element software is used to analyze the water friction loss of motor and calculate the rotor temperature field .The rationality of the model and the validity of the calculated value are verified by the experimental results, which lay a theoretical foundation for the optimum design of high-voltage wet submersible motor for future application.

Effect of repetitive square voltage frequency on partial discharge features

The inverter-fed motor is a key component of environmental-friendly hybrid cars, high-speed trains, and other industrial applications. After the widespread use of inverter-fed motors, the repetitive impulse surges from inverters were found to cause new insulation problems in inverter-fed motors that were linked to premature insulation failure. The partial discharge (PD) induced by the overvoltage inner stator windings was found to be the root cause of insulation reliability problems. To mitigate this problem, PD detection and life testing at repetitive square voltages should be performed on new types of insulation models and entire motor insulation systems. The obtained partial discharge inception voltage (PDIV) and lifetime of insulation in the tests can be used to evaluate the insulation status of inverter-fed motor insulation systems and thus to improve the insulation designs. At AC voltage conditions, the voltage frequency can significantly affect PD activity. At repetitive square voltage with rapid rise time, the influence of the square voltage frequency on PD activity should be investigated (1) to suggest values for the repetitive square voltage frequency selection for the PDIV and lifetime tests, and (2) to increase the signal-to-noise ratio when extracting PD pulses from strong disturbances generated by the operating switch of impulse generators. Therefore, the main purpose of this paper was to investigate the effects of repetitive square voltage frequency on PD events. Insulation models of both Type I (low-voltage inverter-fed motor) and Type II (high-voltage inverter-fed motor) were used to obtain single-PD and multi-PD statistical features, respectively. Experimental results indicated that higher frequencies caused less PD events with lower PD magnitudes and shorter delay times in one square voltage cycle. This phenomenon was attributed to the different surface charge decay ratios and the initial electron emission probabilities resulting from different square voltage frequencies. Finally, a number of considerations for PD measurements on inverter-fed motors were provided to improve the sensitivity of the PD test system and to obtain high objective insulation lifetime test results, which are used to assess the insulation status of inverter-fed motors.

진공차단기 스위칭 써지 특성 해석 및 저감 방안

Vacuum circuit breaker(VCB) has been widely used for interruption of load current and fault current for high voltage motor in the industrial field. Its arc extinguishing capability is excellent compared to other breakers. But it has the potential to cause multi reignition surge by high extinguishing capability. Surge voltage is generated by the opening and closing of VCB. Multi reignition surge of VCB is steep-fronted waveform. It may have a detrimental effect on the motor winding insulation. So, most of users install a protection device to limit steep-front waveform at the motor terminal or breaker side. So, most of users install a protection device at the motor terminal or breaker side. This protective device is surge absorber(SA) such as ZnO and RC type. In this study, we analyzed whether there is any effect when two type SA is applied to the VCB multi reignition surge. We confirmed that ZnO SA is slightly more effective than RC SA for reduction of multi reignition surge.

실란처리된 Epoxy/MICA 콤포지트의 열적, 기계적 전기적 특성연구

In this study, epoxy/mica composite was prepared by mixing with mechanical stirrer together with homogenizer, and the effect of amino-type silane coupling agent was also studied. To reduce the viscosity without any decrement of other properties, 1,4-Butanediol diglycidyl ether (1,4-BDGE) as an aliphatic epoxy reactive diluent was introduced to the epoxy/mica composite in order to use as vanish for high voltage motor and generator stator winding. It was confirmed by scanning electron microscopy (SEM) observation that interfacial characteristics between organic epoxy and inorganic mica was modified by coupling agent treatment so that glass transition temperature increased, and tensile strength and electrical breakdown strength increased. The properties were estimated by Weibull statistical analysis and the ac electrical breakdown strength was 20.2% modified by treating silane coupling agent.

Impact of Geomagnetically Induced Currents Secondary Event on the High-Voltage Synchronous Motors

It is justified that during geomagnetic storms the high voltage synchronous engines are being impacted by high current harmonics of even sequences powered by power transformer due to geo-induced high voltage currents flowed through the windings. Equivalent circuits of step down substation and HV synchronous motors are made for making it possible to consider a saturation of power transformer magnetic system and higher current harmonics availability in stator windings. Analytic expressions for higher current harmonics and extra capacity losses calculation in stator windings are received, as well as the calculation of induction torques allowing to denote a rate of geomagnetic processes impact on synchronous engine operation at various step down substation parameters.

Study on Capacitor Voltage Balancing Control of Modular Multilevel Converter at Low Frequency

 Abstract—This paper describes a control method and the operating performances of Modular Multilevel Converter (MMC) for high-voltage motor drive. The magnitude of capacitor voltage ripples increases when operating frequency decreases. To deal with the significant voltage fluctuation under low frequency conditions, theoretical analysis is presented in this paper, and a new capacitor voltage balancing control strategy is proposed, which is based on carrier phase-shifted sinusoidal pulse width modulation (CPS-SPWM). The simulation results show that MMC works well and capacitor voltages are balanced with the control strategy at low frequency.