In terms of the characteristic of instantaneous magnetizing inductance reflecting the saturation stage in transformer, an improved method is proposed to distinguish between the magnetizing inrush current and short-cir...
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In terms of the characteristic of instantaneous magnetizing inductance reflecting the saturation stage in transformer, an improved method is proposed to distinguish between the magnetizing inrush current and short-circuit fault based on the ratio of average equivalent instantaneous inductances between the non-saturation and the saturation zone, which are divided according to a threshold of differential current. During the inrush, the value of equivalent instantaneous inductance varies severely from small to large as the transformer entering into the saturation and withdrawing from it, so the ratio of average equivalent instantaneous inductances between the non-saturation and the saturation zone is very large in one cycle. However, for the short-circuit fault in transformer, the equivalent instantaneous inductance is very small, and keeps little variation, so the ratio is approximately equal to one. The principle and setting of this method is simple and easy, and its identification time is short. The experimental results verify that the method is correct and effective
In the medium voltage adjustable speed drive (MV-ASD) systems, low switching frequency results in high harmonics in the output voltage waveform, which is harmful to the isolation of the induction motor. Therefore, the...
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In the medium voltage adjustable speed drive (MV-ASD) systems, low switching frequency results in high harmonics in the output voltage waveform, which is harmful to the isolation of the induction motor. Therefore, the power filter is usually set between inverter and motor. However, self-excitation oscillation easily occurs under this structure due to the filter capacitor, which could continuously bring up the DC-link voltage of the inverter, and even destroy the devices in inverters. One of the effective ways to eliminate the self-excitation oscillation is to set the inverter to three-phase short-circuit braking state, which is described and analyzed in detail in this paper. Three-phase short-circuit braking could be easily realized in the inverter-motor system. It can be verified by both simulation based on PSIM and test results that this is an efficient way in real applications. Finally, the characteristics of the short-circuit braking is summarized and beneficial suggestions on using this braking method are presented
The permanent magnet assisted synchronous reluctance (SR-PM) machine can not only offer higher torque capacity and improved power factors compared with the conventional synchronous reluctance machine, but also own wid...
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The permanent magnet assisted synchronous reluctance (SR-PM) machine can not only offer higher torque capacity and improved power factors compared with the conventional synchronous reluctance machine, but also own wider adjustable speed range compared with the permanent magnet machine. This paper presents a new method to optimize the key parameters of the machine under keeping the torque of the machine as large as possible by controlling the stator current. Nonlinear optimization and functional analysis are used to obtain the maximal torque at a certain speed. The investigation of many groups of the parameter data shows that the performance of a machine is influenced by various factors such as magnetic materials, the quantities of the material in the rotor, the turns of windings in the stator and so on. The best one should be chosen for applications. The trend of all the curves verifies the simulation results.
Computer control and monitoring system (CCMS) is quite important for high power converters (HPCs) operation. This paper presents a novel CCMS, which integrates a database management system (DBMS) into the monitoring s...
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ISBN:
(纸本)7506274078
Computer control and monitoring system (CCMS) is quite important for high power converters (HPCs) operation. This paper presents a novel CCMS, which integrates a database management system (DBMS) into the monitoring software to get the beneficial features such as simple configuration and compact structure. In its communication system, an advanced optical fiber communication (OFC) technology is applied and priority-based communications is proposed to improve the reliability and the real time of the communications. Furthermore, a friendly standard Windows human-machine interface (HMI) is provided. The reliability and performance of the system are verified by system tests and practical operations.
Two axially-laminated glued axially-laminated synchronous reluctance permanent magnetic (SR-PM) motors are designed and tested. Compared to general axially-laminated synchronous reluctance (SR) motors, the steel brack...
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Two axially-laminated glued axially-laminated synchronous reluctance permanent magnetic (SR-PM) motors are designed and tested. Compared to general axially-laminated synchronous reluctance (SR) motors, the steel bracket is replaced with iron lamination for reduction of iron loss in rotor. The axially-laminated iron and magnet are glued on the bracket with high strength cement with the help of special clamping device. Then the rotor is grinded to the cylinder and a stainless steel rotor sleeve is added to enhance the strength. The design flow starts with initial sizes trade-off and static performance analysis followed by high speed performance validation and dynamic operation simulations. The electromagnetic parameters measurement, no-load and load test are carried out on test bed to verify the design. The comparison of these two sample motors are given for future design reference. It can be concluded that very poor max energy product PM material is not a good choice for application that requires high power density
In view of the impossibility of current measurement in actual grounding plane in power electronic equipment, an equivalent circuit model is set up in this paper using the partial element equivalent circuit (PEEC) meth...
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In view of the impossibility of current measurement in actual grounding plane in power electronic equipment, an equivalent circuit model is set up in this paper using the partial element equivalent circuit (PEEC) method to simulate and calculate current distribution in grounding plane. The inductance parameters calculated are fairly coincident with experiment results, and some conclusions of current distribution are summarized. It is shown that the equivalent circuit model using PEEC method presented in this paper is a feasible and promising way to model and calculate current distribution in grounding plane
This paper presents an accurate flux observer used in distributed multi-processor (DMP) adjustable speed drive systems. The stator flux linkage is estimated with a full-order observer, while the rotor speed is identif...
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This paper presents an accurate flux observer used in distributed multi-processor (DMP) adjustable speed drive systems. The stator flux linkage is estimated with a full-order observer, while the rotor speed is identified by using Lyapunov theorem. In order to improve the system performance in a wide speed range, the stator resistance is estimated simultaneously. In this paper, the structure of the DMP system, the principle of the full-order observer and the method for identifying the rotor speed and state resistance are all described in details. Relevant simulation results based on MATLAB/SIMULINK are given to prove the performance of the method. Experiments of a real system also verify the feasibility of this scheme
The voltage increment in MV-ASD systems deteriorates the electromagnetic environment, therefore the communication system is facing a formidable challenge in the attempt to achieve the numerous real-time interactivitie...
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The voltage increment in MV-ASD systems deteriorates the electromagnetic environment, therefore the communication system is facing a formidable challenge in the attempt to achieve the numerous real-time interactivities among those subsystems under such electromagnetic circumstance. This paper focuses on the real-time communication system for the MV-ASD systems, in which electromagnetic compatibility (EMC), real-time performance and system reliability are considered simultaneously. A novel fiber-CAN network is designed and implemented, which remarkably increases EMC compared to the conventional ones. The CAN system that serves in the multiprocessor controlsystem for the MV-ASD system with the rated power of 1 MW is implemented. From the experiment results in the MV-ASD system with a 690 kW motor, it can be verified that the requests of timing performance and the reliability for the communication system are well accomplished
Based on the simulation of ultraviolet (UV) radiation in the Sun's rays and in corona, the aging effect of UV radiation on composite insulators was studied in this paper, especially the effect on hydrophobicity pr...
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ISBN:
(纸本)0780385845
Based on the simulation of ultraviolet (UV) radiation in the Sun's rays and in corona, the aging effect of UV radiation on composite insulators was studied in this paper, especially the effect on hydrophobicity properties. It is found that after irradiation with UV, no matter whether a short time of less than 24 hours or a long time of 2000 hours, the hydrophobicity and the hydrophobicity transfer properties of silicone rubber (SIR), which are described by contact angle, slowly turns better. Four different kinds of samples with different prescriptions were used in the test. As UV sources, a special setup to simulate the UV rays of corona and a xenon light to simulate the sunlight were both used. The change of rigidity of silicone rubber was also measured. Infrared spectra of the silicone rubber surface, irradiated by UV for various times, show that the content of the low molecule weight on the surface is different, and this can be due to the discrepancy of hydrophobicity properties of the samples.
In this paper, high-density polyethylene (HDPE) films were prepared by three kinds of annealing methods which were different in cooling speed. The crystallinity of those HDPE samples were measured and compared. A high...
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In this paper, high-density polyethylene (HDPE) films were prepared by three kinds of annealing methods which were different in cooling speed. The crystallinity of those HDPE samples were measured and compared. A high DC voltage was applied to the samples and the space charge formed was measured. Homo-charges were found in samples that were applied with a negative high voltage. The space charge properties were discussed, based on crystallinity. From these results, it is found that the space charge formed in samples cooled at high speed is more than that of the samples cooled at normal and low speed.
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