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Öğe Bearing and misalignment fault detection in induction motors by using the space vector angular fluctuation signal(Springer, 2005) Arkan, M; Çalis, H; Tagluk, METhis paper describes the use of the space vector angular fluctuation (SVAF) method for bearing and misalignment fault diagnosis in induction motors. The theoretical background for SVAF is presented and it is shown how bearing and misalignment faults can be effectively diagnosed by the use of this non-invasive method. The proposed algorithm uses only stator currents as the input, without any other sensors. Both simulation and experimental results carried out on different motors show that these faults could be easily detected and differentiated from each other by fault-related frequencies, which occur in the spectrum of the SVAF.Öğe Closed rotor slot effect on negative sequence impedance(Ieee, 2001) Arkan, M; Kostic-Perovic, D; Unsworth, PJThis paper presents experimental results concerning the negative sequence impedance Z(n) of induction motors with different rotor slot constructions. Z(n) is used as a fault index for shorted turns in stator windings, or can be used distinguish negative sequence current due to unbalanced supply voltage from negative sequence current due to stator shorts. Although Z(n) is largely independent of speed changes, experiments show that it can vary strongly with motor loading. Results presented show that, depending on rotor slot type, negative sequence reactance can change by as much as 10% to 50%, especially in motors with closed rotor slots.Öğe Internal ionization process in polymer dielectrics in strong electrical field(Elsevier Science Bv, 2004) Alisoy, GT; Alisoy, HZ; Rustamov, SA; Arkan, MIn this paper, the effects of internal ionization process, which occur in the voids under strong electrical field, on the polymer dielectrics degradation with time are analyzed. Theoretical equations have been derived for partial discharge V-I characteristic, voltage and discharge current variation with time in the discharge channel, discharge channel cross-section area variation with time and voltage, and channel expansion. The results have shown that approximately 21% of released energy is used for channel expansion and similar to3% of released energy is used for atom ionization when resonant emission and heat transfer are ignored. Effect of discharge impulses on the surface of dielectric for different pi values has been compared. (C) 2003 Elsevier B.V. All rights reserved.Öğe Modelling and simulation of induction motors with inter-turn faults for diagnostics(Elsevier Science Sa, 2005) Arkan, M; Kostic-Perovic, D; Unsworth, PJThis paper presents two orthogonal axis models for simulation of three-phase induction motors having asymmetrical windings and inter-turn short circuits on the stator. The first model assumes that each stator phase winding has a different number of turns. To model shorted stator turns, the second model assumes phase as has two windings in series, representing the unaffected portion and the shorted portion. It uses the results of the first model to transfer phase as to qd so that shorted portion is transferred to the q axis. Simulations results from the models are in good agreement with other studies and are compared with experiment carried out on a specially wound motor with taps to allow different number of turns to be shorted. The models have been successfully used to study the transient and steady state behaviour of the induction motor with short-circuited turns, and to test stator fault diagnostic algorithms operating in real time. (c) 2005 Elsevier B.V. All rights reserved.Öğe Online stator fault diagnosis in induction motors(Inst Engineering Technology-Iet, 2001) Arkan, M; Perovic, DK; Unsworth, PThis paper presents a noninvasive and online method for detection of stator winding faults in three-phase induction motors from observation of negative sequence supply current. A power decomposition technique (PDT) has been used to derive positive and negative sequence components of measured voltages and currents. A fault detection algorithm has been developed to characterise the effects of supply imbalance and nonlinear motor effects (motor iron saturation, winding imbalance, rotor static eccentricity), which also generate negative sequence current. The effects of motor heating and variation in negative sequence resistance with slip change are minimised by using only motor negative sequence reactance to calculate supply negative sequence current. Change in the motor negative sequence impedance under supply imbalance due to load variation (mainly because of closed rotor slots effect) has been included. Experimental results on several motors show that negative sequence impedance can vary between 10% to 50%. Semiempirical formulas based on theoretical and experimental results have been proposed to eliminate the effects of supply imbalance, load, and voltage variation. Compensation for this negative sequence current before making the fault decision enables a high fault sensitivity to be achieved.
