A novel transformer fault diagnosis method using self-powered radio frequency identification (RFID) sensor tag, deep belief network (DBN), and multiple kernel support vector machine (MKSVM) is presented. The self-powered RFID sensor tag is applied to measure transformer vibration signals, which has advantages of convenience, long-term monitoring, low power consumption and fast location. Then, the DBN is employed to extract features from the measured signals, and the DBN method’s extraction performance is improved by optimizing its learning rates and momentum factors. The extracted features of the same fault are highly centralized and features of the different faults are obviously separated. Based on the features, the MKSVM is utilized to construct a transformer fault diagnosis model, and the MKSVM’s penalty factor and kernel weights are optimized through a quantum-behaved particle swarm optimization (QPSO) algorithm. Finally, a mean signal deviation (MSD) metric is presented to locate the fault position. In the experiment, a 10 kV transformer is used to demonstrate the proposed transformer fault diagnosis procedure, and the diagnosis results reflect that the proposed method can effectively measure the transformer vibration signals, extract the essential features, construct an accurate diagnosis model, and locate the fault position.

Numerous studies show that power semiconductors are significant contributors to the overall failure rate of PWM voltage source rectifier (VSR) systems. Aimed at this problem, this paper presents an improved diagnosis system for opencircuit faults of a three-phase PWM VSR based on AC current distortion characteristics, which consists of a diagnosis module, a register module and a decision module. The diagnostic module employs a hysteresis comparator to judge the change trend of the currents, and thereby diagnoses the single OC faults. The register module is employed to achieve multi-switch OC fault diagnosis, and the decision module is used to output the final result. The proposed method extends the previous work to multi-switch OC fault conditions as well as improves the diagnosis accuracy. The experimental results show that the proposed method can correctly achieve fault diagnosis, including 6 kinds of single switch faults and 15 kinds of different double switches faults. Additionally, the proposed method also shows superior antiinterference performance and high robustness on abrupt load transient conditions, different power factor conditions, unbalanced and/or distorted grid voltage conditions and different AC filter structure conditions. Furthermore, the average diagnostic time of this method is only 3.68 ms.

This paper presents a passive wireless humidity sensor for concrete monitoring. After discussing the transmission of electromagnetic wave in concrete, a novel architecture of wireless humidity sensor, based on Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) technology, is proposed for low-power application. The humidity sensor utilizes the top metal layer to form the interdigitated electrodes, which were then filled with polyimide as the humidity sensing layer. The sensor interface converts the humidity capacitance into a digital signal in the frequency domain. A two-stage rectifier adopts a dynamic bias-voltage generator to boost the effective gate-source voltage of the switches in differential-drive architecture. The clock generator employs a novel structure to reduce the internal voltage swing. The measurement results show that our proposed wireless humidity can achieve a high linearity with a normalized sensitivity of 0.55% %RH at 20 °C. Despite the high losses of concrete, the proposed wireless humidity sensor achieves reliable communication performances in passive mode. The maximum operating distance is 0.52 m when the proposed wireless sensor is embedded into the concrete at the depth of 8 cm. The measured results are highly consistent with the results measured by traditional methods.

Due to its low harmonic, high efficiency and high power factor (PF), the multi-pulse autotransformer has been frequently used in the aviation sector. Many studies have been carried out on the theoretical calculation and simulation analysis of the autotransformer. However, the practical application of the multi-pulse rectifier in practical engineering field is inevitable. This work investigates an 18-pulse rectifier power supply of 11 kW being constructed using a multi-pulse autotransformer to suppress the harmonics of a radar power system, in which the parameters of the various parts are designed in detail, and test results are simulated using MATLAB/Simulink software. The actual test suggests that, at the rated condition, the PF of the rectifier is 0.99, the total harmonic distortion (THD) of the input current is below 6.7%, and the efficiency is more than 96%. The power supply is successfully applied to the radar power supply system of a large transport aircraft, and meets the requirements of an environmental test. Furthermore, the results also provide powerful application support for the power supplies and distribution systems in other fields.

This paper firstly introduces the importance of temperature control in concrete measurement, then a passive radio frequency identification (RFID) sensor tag embedded for concrete temperature monitoring is presented. In order to reduce the influences of concrete electromagnetic parameters during the drying process, a T-type antenna is proposed to measure the concrete temperature at the required depth. The proposed RFID sensor tag is based on the EPC generation-2 ultra-high frequency (UHF) communication protocol and operates in passive mode. The temperature sensor can convert the sensor signals to corresponding digital signals without an external reference clock due to the adoption of phase-locked loop (PLL)-based architecture. Laboratory experimentation and on-site testing demonstrate that our sensor tag embedded in concrete can provide reliable communication performance in passive mode. The maximum communicating distance between reader and tag is 7 m at the operating frequency of 915 MHz and the tested results show high consistency with the results tested by a thermocouple.