Kumar V Jagadeesh

Bio: Kumar V Jagadeesh is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Bushing & Transformer. The author has an hindex of 3, co-authored 5 publications receiving 23 citations.

Tunneling magneto-resistor based angle transducer

Abstract: An angle transducer that provides a linear output for full-circle range (0–360°) of operation is presented in this paper. The sensor part of the transducer is made of two pairs of Tunneling Magneto-Resistors (TMR) and the signal conditioning part consists of a couple of sinusoids having same frequency but differing in phase by 90° and a phase detector. The novel signal conditioning circuit proposed here operates on the sine/cosine outputs of the TMRs and provides a voltage that is linear to the angle being sensed. Simulation studies conducted using SPICE demonstrate the efficacy of the transducer in providing a linear output across the entire full-scale range with a worst case error less than ± 0.15 %. Results obtained from a prototype unit built and tested establish the practicality of the proposed transducer. The worst case error of the prototype was < ± 1 %.

Online assessment of winding deformation based on optimised excitation

Abstract: On line assessment of winding deformation in a power transformer can be performed via a bushing tap excitation with optimized high frequency excitation. A benchmark layer winding is used to validate the use of the specific high frequency excitation. Axial displacement, compression and buckling of the winding are simulated and the changes identified. Measurements are performed on a voltage transformer to verify the suitability of the technique. The procedure will result in a considerably shorter time for measurement.

A novel measurement technique for performance comparison of sun tracker systems

Abstract: Comparative performance analysis of fixed or oriented (single axis or twin axis type) sun tracking systems in the field requires that the solar PV arrays mounted on the test tracker and the reference tracker, not only have to be identical, but also tested under identical operating conditions. In order to satisfy the above criteria as well as to extract the maximum output, the identical operating condition for a comparison test is chosen to be the maximum power point operation. Use of an electronic load, realized with a MOSFET serving as a variable load resistor, in conjunction with a microcontroller for maximum power point operation of a PV array during such comparative tests is presented in this paper. A prototype measurement system based on the proffered technique is developed to carryout comparison studies on sun tracker systems in the filed. Using the prototype, tests were conduced to compare the performances of a fixed PV array system and a two step, stepwise manual tracker. Simulation results and experimental results obtained using a prototype unit built and tested establish the efficacy of the proposed technique for proper comparison of sun tracking systems, in the field.

Successive Approximation Type Direct Displacement to Digital Converter Suitable for Floating-Wiper Resistive Displacement Sensor

Abstract: A novel signal conditioning circuit that operates on a floating wiper resistive displacement sensor and provides a digital output proportional to the displacement of the wiper is presented here. Floating wiper resistive displacement sensors possess long operational life due to reduced wear and tear as the wiper does not rub against the resistive element. However, the air gap between the floating wiper and the resistance introduces a coupling capacitance whose value varies as the wiper moves, making it difficult to obtain an output proportional to the displacement of the wiper. The successive approximation logic-based method presented here, operates on a floating wiper resistive displacement sensor and provides a digital output that is linear to the displacement of the wiper. More importantly the output is independent of the value of coupling capacitance. The efficacy of the scheme has been established through simulation studies, the results of which are also presented here.

On-line assessment of moisture in a power transformer

Abstract: An online method for the assessment of moisture in a power transformer is presented in this paper. It is experimentally tested on simple insulating materials as well as on a sample bushing insulation. It is finally tested during the drying of a 110 kV transformer. The results are presented and show that the method is clearly able to distinguish between levels of moisture in the range of interest.

Current Status and Future Trends in Frequency-Response Analysis With a Transformer in Service

Abstract: This paper presents the current status and future trends in the application of the frequency-response analysis (FRA) technique with the transformer in service (online) through bibliographic review and analysis. As a result, three basic stages of the online FRA test have been identified and defined: injection and excitation signal measurement; recording, filtering and processing of measured signals; and curve analysis and interpretation. This work presents an overview of the online FRA technique, useful for subsequent research in this area.

A Novel PLL Resolver Angle Position Indicator

Abstract: This paper describes a novel and high-performance phase-locked loop (PLL) resolver converter for the measurement of mechanical angles. The proposed method does not require the use of demodulators, voltage-controlled oscillator, digital-to-analog converter, counter, and lookup tables, that are associated with conventional PLL converters. The proposed method employs full-wave rectifiers to obtain the absolute values of the modulated resolver signals. This scheme results in a triangular output voltage and two binary outputs that represent a measure of the input angle. The required sine and cosine of the estimated angle, which are needed for PLL converters, are determined using simple approximation techniques. The proposed method can be used to measure angles in the full 360° range, is simpler than the available techniques, and may be easily implemented using digital or basic analog electronic circuitry. This paper describes the proposed method, full details of its implementation using standard electronic components, and experimental results. The performance of the proposed converter is comparable with that of a commercial product.

Position Measurement Using Sinusoidal Encoders and All-Analog PLL Converter With Improved Dynamic Performance

Abstract: This paper describes a phase-locked loop (PLL) converter with improved dynamic response for the determination of mechanical angle from sinusoidal encoders and resolvers. PLL converters are tracking-type converters that use the sine and cosine signals of the transducer in a closed-loop arrangement aiming to match an estimated output angle to the true angle encoded in the sine and cosine input signals. Such a scheme requires means to determine the sine and cosine of the estimated output angle; conventional converters achieve this by using voltage-controlled oscillators, digital-to-analog converter (DAC), counter, and lookup tables. The proposed converter simplifies implementation by making use of the estimated output angle signal to approximate its sine and cosine using analog triangle-sine conversion technique. A new method is also proposed to enhance the dynamic performance of the converter enabling near instantaneous response. This paper describes the proposed method, full details of its analog implementation, and experimental results. Results demonstrate agreement with theory and computer simulation.