MATHEMATICAL MODEL OF OVERHEAD PARAMETRIC EDDY CURRENT PRIMARY MEASURING TRANSDUCER OF ABSOLUTE MOVEMENT

To date, even in the developed countries of Europe, more than 50% of the power generating equipment of hydropower plants have worked their design life. In the CIS countries, the percentage of such equipment is even higher. The complete replacement of such equipment requires a large amount of investment, while a significant part of the latter has a satisfactory technical condition for the further extension of the service life. However, with an increase in the operating time of every electrical equipments, the probability of its failure inevitably increases, which can lead to significant material losses and to a significant danger to the life and health of the power plant personnel. Therefore, in view of the foregoing, monitoring and early diagnosis systems, which are entrusted with the protection function of both hydraulic turbines and auxiliary power equipment, are becoming increasingly relevant. One of the most promising methods of technical control and diagnostics of hydraulic units is the analysis of their vibro-acoustic characteristics. Including the axial component. However, a significant technical problem that arises in the construction of such systems is the limited use of known absolute vibration displacement sensors due to the lack of their high-precision mathematical models. In the article a mathematical model of an overhead parametric eddy current primary measuring transducer of absolute displacement has been developed. It is shown that both the effective value of the output current and the shift of its initial phase are found to be functionally dependent on the distance between the sensor and the conductive medium with a stable supply voltage. It has been established that, while ensuring acceptable overall dimensions, this sensor has sufficient sensitivity to convert the displacement to the effective (amplitude) value of the output current, which is constant in the range of movement from 0 to 5 mm, to ensure the required measurement accuracy.

Rationale for the parameters of the measuring transducer in RFID technology with inductive coupling

In the work the technology of radio-frequency identification of objects with inductive coupling is considered, using passive electric oscillating circuits tuned to fixed frequencies from the working frequency range as identification features of the object. The choice of the primary measuring transducer and the informative parameter is based on the results of the analysis of the system of inductively coupled active and passive electric oscillation circuits, known from the theory of radio engineering circuits. The parameters of the measuring transducer ensuring the fulfillment of the requirements for identification and localization of objects specified by technological conditions are substantiated. Factors that are potentially dangerous with respect to reducing the information reliability of the measuring transducer are considered, as well as the possibility of reducing their influence to a minimum. The problems of experimental research are formulated. It is shown that the analysis can be performed by software discrete adjustment of the primary measuring transducer and the generator feeding it. In this case, the task of increasing the speed is targeted at decreasing the duration of the step of tuning the primary measuring transducer. The required reliability of object identification is achieved by: ensuring high stability of the frequencies of the generator supplying the primary measuring transducer; accuracy and stability of tuning of the primary measuring transducer to the frequencies of the supplying generator; protection of the primary measuring transducer from the influence of interference generated by external sources and other measuring converters of the object identification system (electromagnetic compatibility of the object identification system); sufficient magnitude of the response of the primary measuring transducer to the introduction of passive electrical oscillation circuits; sufficient frequency tuning interval for passive electric oscillation circuits; accuracy and stability of tuning of passive electric oscillation circuits; stability of the detection threshold relative to the initial level of the informative parameter. Electromagnetic compatibility of measuring transducers, whose sensing elements are in the zone of mutual influence, is provided by synchronizing the operation of measuring transducers with shunting of inactive sensors, screening, mutual orientation and spacing of sensing elements.