An electro-quasistatic analysis of an induction micromotor has been realized by using the Cell Method. We employed the direct Finite Formulation (FF) of the electromagnetic laws, hence, avoiding a further discretization. The Cell Method (CM) is used for solving the field equations at the entire domain (2D space) of the micromotor. We have reformulated the field laws in a direct FF and analyzed physical quantities to make explicit the relationship between magnitudes and laws. We applied a primal-dual barycentric discretization of the 2D space. The electric potential has been calculated on each node of the primal mesh using CM. For verification purpose, an analytical electric potential equation is introduced as reference. In frequency domain, results demonstrate the error in calculating potential quantity is neglected (<3‰). In time domain, the potential value in transient state tends to the steady state value.
In this work, we have obtained a new constitutive matrix to calculate the induced Lorentz electric current of in a conductive disk in movement within a magnetic field using the cell method in 3D. This disk and a permanent magnet act as a magnetic brake. The results obtained are compared with those obtained with the finite element method (FEM) using the computer applications Getdp and femm. The error observed is less than 0.1173%. Likewise, a second verification has been made in the laboratory using Hall sensors to measure the magnetic field in the proximity of the magnetic brake.
This work demonstrates the equivalence of two constitutive equations. One is used in Fourier’s law of the heat conduction equation, the other in electric conduction equation; both are based on the numerical Cell Method, using the Finite Formulation (FF-CM). A 3-D pure heat conduction model is proposed. The temperatures are in steady state and there are no internal heat sources. The obtained results are compared with an equivalent model developed using the Finite Elements Method (FEM). The particular case of 2-D was also studied. The errors produced are not significant at less than 0.2%. The number of nodes is the number of the unknowns and equations to resolve. There is no significant gain in precision with increasing density of the mesh.
In this work we analyse the temperature distribution in a conductor disk in transitory regime. The disk is in motion in a stationary magnetic field generated by a permanent magnet and so, the electric currents induced inside it generate heat. The system acts as a magnetic brake and is analysed using infrared sensor techniques. In addition, for the simulation and analysis of the magnetic brake, a new thermal convective matrix for the 3D Cell Method (CM) is proposed. The results of the simulation have been verified by comparing the numerical results with those obtained by the Finite Element Method (FEM) and with experimental data obtained by infrared technology. The difference between the experimental results obtained by infrared sensors and those obtained in the simulations is less than 0.0459%.
In this paper, a new method for characterizing the dielectric breakdown voltage of dielectric oils is presented, based on the IEC 60156 international standard. In this standard, the effective value of the dielectric breakdown voltage is obtained, but information is not provided on the distribution of Kelvin forces an instant before the dynamic behavior of the arc begins or the state of the gases that are produced an instant after the moment of appearance of the electric arc in the oil. In this paper, the behavior of the oil before and after the appearance of the electric arc is characterized by combining a low-cost CMOS imaging sensor and a new matrix of electrical permittivity associated with the dielectric oil, using the 3D cell method. In this way, we also predict the electric field before and after the electric rupture. The error compared to the finite element method is less than 0.36%. In addition, a new method is proposed to measure the kinematic viscosity of dielectric oils. Using a low-cost imaging sensor, the distribution of bubbles is measured, together with their diameters and their rates of ascent after the electric arc occurs. This method is verified using ASTM standards and data provided by the oil manufacturer. The results of these tests can be used to prevent incipient failures and evaluate preventive maintenance processes such as transformer oil replacement or recovery.
In this paper, a new constitutive matrix for thermal conduction in transient thermal regime is developed and tested. We use cell method as a numerical method that is included in finite formulation methodology. The constitutive matrix defines through the cell method the behavior of solids when they are under a thermal potential. We have demonstrated that this matrix is equivalent to the electrical conduction constitutive matrix in steady state. We have applied this constitutive matrix to thermal analysis of asynchronous electric machines in transient regime. This constitutive matrix has been validated with comparisons based on finite element method. In finite formulation, the physical laws governing the electromagnetic fields and the physical thermal phenomena are expressed in integral formulation. The final algebraic equation system is tailored directly without discretizing of the differential equations. This is an important advantage because we omit a complex differential formulation and the discretization of the respective equations.
Reducing power consumption leads to improve wireless sensor autonomy, increase battery life, and reduce radiated power. State-of-the-art blood pressure sensors based on piezoresistive transducers in a full Wheatstone bridge configura tion uses low ohmic values because high sensitivity and low noise approach. In this work, the piezoresistance values are increased in order to reduce one order of magnitude the power consumption.The noise introduced by this improvement was proved that does not limit the accuracy for 8-bit applications. Therefore, a low power consumption pressure sensor with high sensitivity and low noise is proposed. Power consumption versus sensitivity tradeoff is analyzed in detail. I. IN T RODUCTIONWireless blood pressure sensors are especially suitable for surgery rooms, intensive care or post-anesthetic recovery units, even small laboratory animals. Low power consump tion is a critical point to improve the distance between the wireless sensor and monitoring equipments and improve the battery life of the sensors, reducing at the same time the power radiated to establish the wireless communication. State of-the-art blood pressure transducers, based on four resis tors in a full Wheatstone bridge configuration, are usually optimized for sensitivity [1]-[3] and linearity. Temperature effect on sensitivity in silicon piezoresistive transducer has been studied in detail in [3]- [5]. Analysis of the noise in piezoresistive transducer has been presented in [5]. Most of the piezoresisitive transducer are ion-implanted into a thin silicon monocrystalline membrane. Ty pical values are in the range between 100 fl and 3 kfl, powered between 3 V and 5 V. This means a power consumption between 3 m W and 250 m W, typically 20 mW, only for the full Wheatstone bridge without the required signal conditioning circuit -a signal conditioning circuit with at least one operational amplifier is required.In this work, the piezoresistance ohmic values are increased in order to reduce the power consumption. It was proved that the noise introduced by this improvement does not limit the accuracy for 8-bit applications. The achieved power con sumption results are below 322 /-l W, including both the full Wheatstone bridge (62/-lW) and the signal conditioning sys tem, for a mixed signal technology of 1.0 /-lm CMOS process, including integrated sensors -XC 10 technology process from XFAB. This work proposes optimal tradeoff design points for piezoreslstlve transducer and sensor in terms of sensitivity, power consumption and noise. This paper is organized as follows. In Section II mechanical behavior of a diaphragm -pressure sensor-is analyzed in detail. In addition, the layout dimensions and positions of several piezoresistances -250, 500 and 1000 kfl-are calculated. The analysis of both sensitivity and power consumption of a full Wheatstone bridge and differential amplifier circuit to achieve optimum power and sensitivity design points is presented in Section m. Finally, conclusions are presented in Section IV. II. ELECTROMECHAN...
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