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DC-link capacitor is one of the reliability-critical components in motor drive applications, which contributes to a considerable cost, size and failure. Its reliability performance depends on both inherent physical strength and external loading. The grid unbalances could alter the electro-thermal stresses of key components in a motor drive. Therefore, this paper investigates the impact of grid voltage...
In recent years, the introduction of solar power generation equipment has increased as distributed power supply has increased. A power conditioning subsystem (PCS) of a solar power generation system is an apparatus using an integrated circuit. Switching noise is generated because the inverter, which is the main constituent element of the PCS, performs DC-AC conversion through high-frequency switching...
This paper describes two concepts of automatic systems for accuracy testing of current transformers. Advantages and disadvantages of both concepts are discussed. The concept of multi channel testing is used for developing of the measuring device for current transformer accuracy testing for factory FMT Zajecar. The short description of the device is presented as well as the results of its testing.
This paper describes the design and testing process of low power current sensors using PCB rogowski-coil for high current application. The design and testing process of PCB rogowski-coil transducer and electronic circuit are explained in deeply analyze based on the physical structure. It also reveals the linearity and error rates of PCB rogowski-coil current sensors. Tests carried out using Current...
Precise control methods of the electric drives with induction machines like field oriented control (FOC) or direct torque control (DTC) need an accurate model of the machine they control. Certain parameters of the model have to be obtained with sufficient accuracy before the drive can be put into the operation. This article concerns an offline parameter identification method that is suitable for on-site...
A system for evaluating instrument current transformer errors using a lock-in amplifier is described in the paper. The difference between the standard and the transformer under test is evaluated as the ratio error and the phase displacement. The attention is focused to measurement of errors at the range of primary currents less than 20% of the nominal value. The measurement accuracy of current and...
This paper investigates significant changes in the performance of switch-mode power supplies used in standard desktop PCs (PC-SMPS'), which might occur when a PC-SMPS transfers from high to low operating powers. Using the experimental results, it is shown that due to a partial discharging of dc link capacitor at low powers, the input ac current of tested PC-SMPS' loses its periodicity with supply...
In standard power cycling tests, forward conduction generates heat in the die and therefore the ther-momechanical stress in the package. In application, however, a significant part of the power losses are switching losses, so that the load current is lower than in standard power cycling test, for an equal temperature swing. A new concept for power cycling tests is presented, which allows the generation...
The Phasor Measurement Unit (PMU) is a modern instrument that measures magnitude, phase angle, frequency and rate of change of frequency (ROCOF) from voltage and current signals in electric networks. It is designed to be used in the monitoring and control of electric transmission systems. For each measurement, the PMU assigns a timestamp from an accurate time source; in this way, it is possible to...
Renewable energy resources have become an integral part of the power and energy industry in the world today. Photovoltaic (PV) systems are one of the most common and established forms of renewable energy technologies. With the increased installation of PV systems both on a small and large scale, it is critical that the impacts and operations of PV systems are accurately modeled, simulated and studied...
An estimator of the dynamic state of an electric power system (EPS) is presented in this paper. The developed algorithm involves two stages which are based on the weighted least square (WLS) technique. The first stage uses conventional measurements (delivered by RTU — SCADA meters) and synchronized phasor measurements (delivered by PMU meters) in order to estimate the state of the system forming an...
In order to assess the microshock risk, the automatic detection of currents during surgery is important. To this aim, a prototype, called Protegemed, was designed. In order to introduce the device in Italian operating rooms the compliance assessment with international standards is essential. The results of some electrical safety tests and the identification of a measuring method to detect the microshock...
The photovoltaic (PV) array is one of the main components of the PV system, and the accuracy of the PV array model is directly related to the validity of the simulation results. The parameters of the PV array may change with the operation conditions. Therefore, it is important to identify the parameters of the PV array model according to the measured data. In this paper, the conventional four-parameter...
According to the problem of high cost of standard apparatuses and complex operating for the traditional AC current measurement, this paper introduces a method to measure the AC current with high performance which is based on using digitizing system and the AC-DC difference calculable resistance. Compared verification tests indicate a maximum deviation of 2.3 × 10−5 between the digital sampling measurement...
A control circuit to stabilize the flux of electrons transmitted through an extractor electrode is presented. By controlling the emission current a fluctuation with a standard deviation of 0.015% is observed. However, the achievable stability of the transmitted electron current is limited due to a variation of the extraction grid current ratio showing a standard deviation of 4.33%. By regulating the...
In this paper, a portable field inspection device based on industrial control computer is developed, which is used to carry out electrical performance test, charging interoperability test and electric energy metering test of singlephase or three-phase AC charging pile. The paper describes the field inspection principle, system structure test process and technical parameters of the device, and finally...
In this paper, we present a technique for local measurements of the surface potential in the presence of a biasing current flow through a sample. This technique can be implemented by using standard scanning tunneling microscopy (STM) equipment. It is demonstrated that this potentiometry technique can be useful for in-situ sample characterization in ultra-high vacuum (UHV).
Nowadays, one standard therapy for advanced heart failure is the implantation of left ventricular assist devices (LVAD). The LVAD is a mechanical pump, which supports the heart to pump blood to the rest of the body. However, there are serious complications including pump thrombosis. Pump thrombosis is a formation of blood clot inside the LVAD pump, which can result in pump stop and worst case leads...
Objective measurement is an essential part of the assessment process in neurological dysfunction such as stroke. However, current clinical scores are insensitive and based on subjective observation from experts. Technology provides an opportunity for enhanced accuracy and specificity of objective measurement. This study describes the use of an interactive force-sensitive table-top platform for the...
In the process of the lens production it is extremely important that a total time of measuring the lens thickness, taking into account also the time needed to insert the lens into a system, should be short enough to test the substantial part of the series of products. Currently used methods of measuring lens thickness apply various solutions [1, 2], but none of them offers a fast and cost effective...
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