http://hdl.handle.net/10016/10431 Sun, 26 May 2013 07:57:49 GMT 2013-05-26T07:57:49Z http://hdl.handle.net/10016/11214 Title: Inductively coupled probe for the measurement of partial discharges Author(s): Robles, Guillermo; Martínez-Tarifa, Juan Manuel; Rojas-Moreno, Mónica; Sanz Feito, Javier Abstract: Partial discharges are a transient phenomena whose measurement is remarkably important for electrical equipment diagnosis and maintenance. These discharges appear in the measurement circuit as very narrow current pulses of some nanoseconds. Therefore, discharge pulse detection is a particularly difficult problem, especially because they are superposed on the high voltage waveforms that cause them. In this paper, we present an inductively coupled probe able to measure this physical phenomenon by means of a very simple and inexpensive device that can be installed. in the equipment under test. After modeling the probe, its response will be compared to that of commercial devices using both calibrated discharges and partial discharges occurring at real power Wed, 30 Apr 2008 22:00:00 GMT http://hdl.handle.net/10016/11214 2008-04-30T22:00:00Z http://hdl.handle.net/10016/11002 Title: Study of an inductive sensor for measuring high frequency current pulses Author(s): Rojas-Moreno, Mónica; Robles, Guillermo; Tellini, Bernardo; Zappacosta, Carmine; Martínez-Tarifa, Juan Manuel; Sanz Feito, Javier Abstract: The objective of this paper is to present a simple sensor based on Faraday’s Law together with an integration and amplifying stage and used this for measuring fast current pulses. Its behavior in time and frequency is tested by measuring Partial Discharges (PD) in electric insulation systems following the guidelines given in the standard IEC 60270. The measurements are also taken with two other sensors, a commercial high frequency current transformer and a resistive transducer, with the aim of comparing the results obtained with the proposed probe and obtaining an estimation of its sensitivity. An estimation of the uncertainty of the measurements is also calculated obtaining an error similar to other commercial devices. Sat, 30 Apr 2011 22:00:00 GMT http://hdl.handle.net/10016/11002 2011-04-30T22:00:00Z http://hdl.handle.net/10016/10440 Title: Frequency domain modelling of random wound motor windings for insulation stress analysis Author(s): Martínez-Tarifa, Juan Manuel; Amarís Duarte, Hortensia; Sanz Feito, Javier Abstract: The use of conventional low voltage induction motors fed by pulse width modulated (PWM) inverters has begun to present important problems. These waveforms consist of steep-fronted pulses having very short rise times (about 100 ns in modern IGBT bridges) and high frequency repetition rates (up to 20 kHz) whose immediate consequences are additional electrical stresses in an induction motorrsquos insulation system. In this paper a frequency domain model for the analysis and characterization of the internal voltage distribution in random wound coils is presented. The model allows voltage prediction in time domain when an inverse fast Fourier transform (FFT) transformation is performed, and requires only a few frequency domain impedance measurements. This methodology will be useful for accurately predicting the voltage distribution in motor windings during the design stage, and reducing the risk of premature failure in motor insulation. Experimental and theoretical results are presented and compared and model effectiveness using different approximations is studied. Wed, 31 May 2006 22:00:00 GMT http://hdl.handle.net/10016/10440 2006-05-31T22:00:00Z