High-voltage Motor Research Articles

Influence of Single/Dual Ventilation Path on Fluid Field and Temperature Field of HVLSSR-PMSM with Air-Cooled Hybrid Ventilation Systems

Due to the solid rotor structure, High-Voltage Line-Start Solid Rotor Permanent Magnet Synchronous Motor (HVLSSR-PMSM) operates with high rotor temperature rise. If the ventilation path cannot take the rotor heat away in time, the rotor will overheat or even may led to the thermal demagnetization for permanent magnet. Therefore, it is of great significance to study the thermal issues of HVLSSR-PMSM. In the paper, the fluid field and temperature field of a 315 kW, 6 kV HVLSSR-PMSM with air-cooled hybrid ventilation systems are investigated. Firstly, the electromagnetic analysis of the machine is done by using the finite-element method, the loss distributions then are obtained, which will be assigned as the heat source for thermal analysis. Then, the three -dimensional (3-D) fluid thermal coupled mathematical model for thermal analysis of HVLSSR-PMSM is established. The temperature field and the fluid flowing state of HVLSSR-PMSM with single ventilation path air-cooled system are investigated by using the established 3D fluid thermal coupled mathematical model. A dual ventilation path air-cooled system for HVLSSR-PMSM is proposed to reduce the operating temperature rise. Then, the temperature field and fluid field of HVLSSR-PMSM with dual ventilation system are analyzed by comparing with single ventilation system. Moreover, the temperature experiments are carried out on the machine with dual ventilation system to validate the accuracy of the established mathematical models. The results show that the proposed dual ventilation path air-cooled system can effectively improve the thermal distribution of HVLSSR-PMSM, whilst it can also reduce the working temperature rise of the machine.

진공차단기 다중 재발호시의 서지 특성 해석

Vacuum circuit breakers are widely used as power switches for high voltage motors. This breaker generates a high switching surge voltage at the time of opening under lower power factor conditions such as start-up or no-load. When the breakdown voltage of the vacuum interrupter is lower than the transient recovery voltage, high frequency current flows and multiple reignition phenomena occur. Especially, the steep-fronted surge voltage which occurs in multiple re-ignition can act as electrical stress to the motor winding. Therefore, it is necessary to identify the causes and measures to reduce the electric stress.BR In this paper, we analyzed the effect of steep surge voltage and its reduction method when multiple reignition and high frequency quenching current occurred under the condition that the high voltage induction motor is shut off immediately.

Heat transfer characteristics of external ventilated path in compact high-voltage motor

This paper investigates the heat transfer characteristics of the external ventilated path of a compact, 6 kV, 4-pole, 2500 kW motor using flow-thermal coordination mechanism. A computational model is set up and validated by experimental test results. A series of simulation is performed. It is found that the deflection angle α and outlet angle β of the fan blades are the key parameters affecting the efficiency of the cooling effect of the fan. Optimal measures are adopted by changing the deflection angle and outlet angle of fan blades. External fan efficiency is improved from 28.80% to 29.96% and outlet flow is increased by 0.08 m3/s by optimizing the deflection angle α and outlet angle β. According to the optimization results of external fan, heat transfer characteristics and temperature distribution of the cooler is obtained by the fluid and temperature coupling field. The cooler is optimized by adjusting the height of the windshield, increasing the number of the windshield, changing the shape of inclined plate. It is found that the temperature of hyperthermal fluid of inner ventilated path is decreased from 75 °C to 53.7 °C; at the same time the temperature of cryogenic fluid of external ventilated path is increased from 23 °C to 49.4 °C. The outlet temperature of internal fluid of post-optimized cooler is dropped by 3 °C, and the external fluid temperature is increased by 2.5 °C. The performance of fan and the cooling effect is improved. The results from this study can provide an effective method for structural optimal design of compact high-voltage motors.

Invariant protection of high-voltage electric motors of technological complexes at industrial enterprises at partial single-phase ground faults

Development results of invariant protection of high-voltage motors at incomplete single-phase ground faults are observed in the article. It is established that current protections have low action selectivity because of an inadmissible decrease in entrance signals during the shirt circuit occurrence in the place of transient resistance. The structural functional scheme and an algorithm of protective actions where correction of automatic zero sequence currents signals of the protected accessions implemented according to the level of incompleteness of ground faults are developed. It is revealed that automatic correction of zero sequence currents allows one to provide the invariance of sensitivity factor for protection under the variation conditions of a transient resistance in the place of damage. Application of invariant protection allows one to minimize damages in 6-10 kV electrical installations of industrial enterprises for a cause of infringement of consumers’ power supply and their system breakdown due to timely localization of emergency of ground faults modes.

Relay protection features of frequency-adjustable electric drive

The features of relay protection of high-voltage electric motors in composition of the frequency-adjustable electric drive are considered in the article. The influence of frequency converters on the stability of the operation of various types of relay protection used on electric motors is noted. Variants of circuits for connecting relay protection devices are suggested. The need to develop special relay protection devices for a frequency-adjustable electric drive is substantiated.

Changes in Insulation Characteristics of High-Voltage Motor Stator Windings with Temperature and Moisture

This research shows that all of the insulation characteristics (insulation resistance, partial discharge, dissipation factor, and alternating leakage current) of HV motor become worse at high temperature. It is also shows that partial discharge and insulation resistance are reduced at moisture absorption. Therefore, to accurately analyze the insulation degradation trend, it is necessary that those tests always be conducted under the same conditions (temperature and moisture content).

Calculation method of reliability of high-voltage winding asynchronous motors

Calculation method of reliability of high-voltage winding asynchronous motors

Analysis of Correlationship between Partial Discharge and Ozone Emission in High Voltage Motor Stator Windings as the Index of the Insulation Diagnosis

In this study, it turned out that the magnitude of Partial Discharges(PD) and the emission of Ozone(O3) were in a strong positive relation by performing insulation diagnostic tests on artificially defect high voltage motor statorwindings. In this sense, the O3 measurements can be a powerful index of the insulation deterioration during normal operation especially in case of surface PD activity.

Precise analytical formula for starting time calculation of medium- and high-voltage induction motors under conventional starter methods

Large medium- and high-voltage (MV and HV) squirrel-cage induction motors are widely used in most industrial processes. Their starting times are very much required for suitable setting of over-current-protective devices and assessing power quality of distribution power system. Mostly, the starting time can be precisely computed from time-domain numerical computation. This approach is rather tedious and time-consuming. Therefore, this paper presents precise analytical formula to evaluate the starting times of large MV and HV induction motors under conventional starting techniques. The motor simplified first-order dynamic model is employed to derive the formula. An accuracy of the newly proposed formula is evaluated by comparing the obtained starting times against those from laboratory measurement and numerical time-domain simulations under full fifth-order motor model. The studied results confirm that the starting times analytically calculated by the proposed compact formula closely agree with the measured and simulated time-domain results.

Calculation of Iron Loss of Medium-sized High Voltage Motor which Have Axial Ventilation Holes in Rotor

When optimizing the ventilation and cooling system of medium-sized high power density asynchronous motor, it is found that the temperature rise of the motor can be greatly reduced after punching the axial ventilation holes in the rotor yoke, but the traditional method based on the magnetic circuit method cannot accurately calculate the motor iron loss of this new structure. In this paper combined with the finite element field-circuit-motion coupled analysis method, taking YXKK355-4, 355kW and YKK400-4, 400kW medium-sized high voltage asynchronous motor for example, a two-dimensional geometric model and mathematical model of the motor are established, then the iron loss calculation method is improved. Using this method not only the iron loss value of the whole motor can be obtained, but also the specific distribution of iron loss in different areas of the motor can be known, and the correctness of the simulation results is proved by experiments.

The Effect of Temperature on Slot Discharge for High Voltage Stator Windings

During the operation of HV (high voltage) motor, the abrasion of stator windings because of vibration caused by electromagnetic force will give rise to slot discharge. Furthermore, the superheat induced by overcurrent or poor heat dissipation will aggravate the slot discharge. To understand the effect of different temperatures on slot discharge, two laboratory experiments, under different temperatures, were carried out to simulate the slot discharge for 120h. The experiment results indicate that the temperature greatly promotes the development of the slot discharge.

The Effect of Temperature on Slot Discharge for High Voltage Stator Windings

During the operation of HV (high voltage) motor, the abrasion of stator windings because of vibration caused by electromagnetic force will give rise to slot discharge. Furthermore, the superheat induced by overcurrent or poor heat dissipation will aggravate the slot discharge. To understand the effect of different temperatures on slot discharge, two laboratory experiments, under different temperatures, were carried out to simulate the slot discharge for 120h. The experiment results indicate that the temperature greatly promotes the development of the slot discharge.

Аналитический метод оценки нагрева обмотки ротора высоковольтных асинхронных двигателей в пусковых режимах

Аналитический метод оценки нагрева обмотки ротора высоковольтных асинхронных двигателей в пусковых режимах

Electric drives of mining installations

Ventilation systems are one of the most important and energy-consuming systems in the manufacturing process of modern mining enterprises. Variable-frequency asynchronous and synchronous electric drives with frequency converters based on self-commutated inverters or variable-frequency synchronous electric drives based on the LCI scheme are considered as advanced drives for ventilation units. When upgrading electric centrifugal fans with slip-ring asynchronous motors and unexhausted performance potential, it is effective to apply a wound-rotor slip-recovery system. A converter with natural commutation with an intermediate dc link is used in the LCI scheme. Robicon frequency converters are used for variable-frequency high-voltage electric motors. An important advantage of these converters is that they can be used for standard 6- and 10-kV motors.

Detection of large induction motor cage failure by novel analysis of the waveform of the start up current

In the case of large induction motors, it is very important to quickly and safely identify the onset of failure. In that way one should take appropriate corrective measures to prevent significant damage. In this paper, the comparative diagnostics between two high-voltage large induction motors using the specific proposed waveform analysis of current during the direct-on-line start is presented. Using the previously recorded signals, a rotating current vector amplitudes for both machines are determined. Their shapes are analysed and the presence of the initial 100Hz stator current component, indicating the existence of a rotor failure, is observed.

Analysis of Correlation Among Partial Discharges, Ozone Emission, and Ultraviolet Radiation in High Voltage Motor Stator Windings

In this research, a normal winding and simulated defective winding were created to examine the correlation between partial discharges, ozone concentration, and ultraviolet radiation in high-voltage motor stator windings. In the simulated defective winding, the semiconductor layer was removed so that discharges could occur easily between the winding surface and the iron core. A high voltage was applied to both normal and defective windings to measure the partial discharge magnitude, ozone concentration, and ultraviolet radiation. Subsequently, the results were compared and analyzed. The electrical partial discharge magnitude, ozone emission, and ultraviolet radiation measurement methods and properties were explained, and all test results and correlations were analyzed.

The Effect of Distributed Parameters on Conducted EMI from DC-Fed Motor Drive Systems in Electric Vehicles

The large dv/dt and di/dt outputs of power devices in DC-fed motor drive systems in electric vehicles (EVs) always introduce conducted electromagnetic interference (EMI) emissions and may lead to motor drive system energy transmission losses. The effect of distributed parameters on conducted EMI from the DC-fed high voltage motor drive systems in EVs is studied. A complete test for conducted EMI from the direct current fed(DC-fed) alternating current (AC) motor drive system in an electric vehicle (EV) under load conditions is set up to measure the conducted EMI of high voltage DC cables and the EMI noise peaks due to resonances in a frequency range of 150 kHz–108 MHz. The distributed parameters of the motor can induce bearing currents under low frequency sine wave operation. However the impedance of the distributed parameters of the motor is very high at resonance frequencies of 500 kHz and 30 MHz, and the effect of the bearing current can be ignored, so the research mainly focuses on the distributed parameters in inverters and cables at 500 kHz and 30 MHz, not the effect of distributed parameters of the motor on resonances. The corresponding equivalent circuits for differential mode (DM) and common mode (CM) EMI at resonance frequencies of 500 kHz and 30 MHz are established to determine the EMI propagation paths and analyze the effect of distributed parameters on conducted EMI. The dominant distributed parameters of elements responsible for the appearing resonances at 500 kHz and 30 MHz are determined. The effect of the dominant distributed parameters on conducted EMI are presented and verified by simulation and experiment. The conduced voltage at frequencies from 150 kHz to 108 MHz can be mitigated to below the limit level-3 of CISPR25 by changing the dominant distributed parameters.

Large-Motor High-Voltage Insulation Systems Testing: Qualification and Acceptance for the Petrochemical Industry

The insulation system of a large, high-voltage (HV) industrial motor stator winding experiences various and significant stresses while in service. Motor manufacturers are responsible for designing and executing detailed test programs that ensure the proven reliability of an insulation system before its use in production. Qualification programs are designed to certify whether an insulation system is designed well enough to sufficiently handle its anticipated usage stress. These programs typically employ a rigorous series of tests for purpose-built samples, including system characterization, electrical breakdown, accelerated life tests, and detailed laboratory analysis. In contrast, factory-acceptance testing of a new rotating machine stator winding must be nondestructive yet still apply sufficient stress to ensure that its insulation system has been manufactured per the design. This article describes the typical insulation system components used for a multiturn form-wound coil design and the stresses that various parts of the system will face while in service. A recommended qualification plan is presented using industry-standard test methods to evaluate the long-term reliability of a vacuumpressure impregnated (VPI) insulation system under sinusoidal-voltage supply. It describes the diagnostic and withstand electrical tests for routine and special acceptance tests, especially those employed for petrochemical industry, where data may be used to establish a baseline condition assessment that is unique to the machine.

A METHOD OF AUTOMATIC DETERMINATION OF THE NUMBER OF THE ELECTRICAL MOTORS SIMULTANEOUSLY WORKING IN GROUP

Purpose. Propose a method of automatic determination of the number of operating high voltage electric motors in the group of the same type based on the determination and analysis of the account data of power consumption, obtained from of electric power meters installed at the connection of motors. Results. The algorithm of the automatic determination program for the number of working in the same group of electric motors, which is based on the determination of the motor power minimum value at which it is considered on, was developed. Originality. For the first time a method of automatic determination of the number of working of the same type high-voltage motors group was proposed. Practical value. Obtained results may be used for the introduction of an automated accounting run of each motor, calculating the parameters of the equivalent induction motor or a synchronous motor.

Assessment and improvements of inorganic insulation for high temperature low voltage motors

The increase of internal temperature capability of electrical machines is a major challenge for building high power density actuators for many applications in transport systems and in aerospace industry. Today, the main limit is the thermal class of the organic Electrical Insulation System (EIS), but a breakthrough toward very high temperature is possible with inorganic insulation technologies. An inorganic EIS is proposed and tested for designing motors able to work permanently up to 500 °C in the heart of windings. After a review of several high temperature (HT°) insulation solutions, the paper focuses on currently available ceramic-coated wires insulated with a very thin inorganic layer, which is a favorable solution for high current densities in machines of small sizes. The electrical limits of this technology are investigated, the weak points of the HT° wire are circumvented using impregnating cements able to provide adequate mechanical and electrical properties up to 500°C for designing HT ° electrical machines fed by a standard PWM inverter connected to the HVDC bus of the more electric aircraft, for example.